污染物对细菌氧化应激的影响

Nanoplastics (NPs), an emergent pollutant in wastewater treatment plants, include both biodegradable and non-biodegradable types, and their impact on the metabolism relationship of bacteria in activated sludge is a valuable investigation. This study explored the impacts of biodegradable polybutylene adipate-co-terephthalate NPs (PBAT-NPs) and non-biodegradable polyethylene NPs (PE-NPs) (0-1.5 mg/L) on the short-cut nitrification-denitrification (SCND) performance of a sequencing batch reactor (SBR), focusing on metabolic links among reactive oxygen species (ROS), extracellular polymeric substances (EPS), and SCND performance. Results showed that alterations in EPS synthesis, oxidative stress, and metabolic intermediate and electron supply in the tricarboxylic acid (TCA) cycle were closely associated with disrupted nitrogen metabolism, accompanied by severe deterioration of SCND performance at different NPs stresses, and PE-NPs induced a stronger inhibition on the SCND performance than PBAT-NPs. Compared to the control without PBAT- and PE-NPs, PE-NPs increased the ROS production by up to 194.17 %, whereas PBAT-NPs induced an increase in the ROS level of 129.28 %. PE-NPs primarily elicited a greater number and more important ROS-generating genes and enzymes than PBAT-NPs. Compared to PE-NPs, PBAT-NPs strongly reduced the protein (PN) level of LB/TB-EPS by affecting a greater number of enzymes, while comparably suppressed polysaccharides (PS) of LB/TB-EPS by disturbing the same number of enzymes. The TCA cycle could join the metabolic associations between ROS and EPS. This study reveals the metabolic correlation by which biodegradable and non-biodegradable NPs induce toxicity in the SCND system, providing a scientific basis for implementing targeted risk mitigation.

Plasticizer dibutyl phthalate (DBP) pollution has received more and more attention. In this study, a DBP degrading bacteria Enterobacter sp. DNB-S2 was found to suffer membrane damage and oxidative stress during DBP degradation. Physiological and transcriptome analysis showed that 100 μmol L-1 anthraquinone-2,6-disulfonate (AQDS) could enhance the ability of strain DNB-S2 for biodegradation of DBP. AQDS adjusted the cell surface structure, including increase levels of hydrophobic and unsaturated fatty acids. These changes increased the chemotactic ability of the strain DNB-S2 to the hydrophobic pollutant DBP and the fluidity of the cell membrane. The expression of methyl chemotactic protein and genes associated with cell membrane-fixed components were up-regulated. AQDS also improved the scavenging ability of ·OH and H2O2 of DNB-S2 by promoting expression genes related to glutathione metabolism, thereby reducing oxidative stress. These results will provide new insights into the biodegradation of DBP.

Since siderophores have been widely exploited for agricultural, environmental, and medical applications, the identification and characterization of new siderophores from different habitats and organisms will have great beneficial applications. Here, we identified a novel siderophore-producing gene cluster in C. necator JMP134. This gene cluster produces a previously unknown carboxylate siderophore, cupriabactin. Physiological analyses revealed that the cupriabactin-mediated iron acquisition system influences swimming motility, biofilm formation, and oxidative stress resistance. Most notably, this system also plays important roles in increasing the resistance of C. necator JMP134 to stress caused by aromatic compounds, which provide a promising strategy to engineer more efficient approaches to degrade aromatic pollutants. ABSTRACT Many bacteria secrete siderophores to enhance iron uptake under iron-restricted conditions. In this study, we found that Cupriavidus necator JMP134, a well-known aromatic pollutant-degrading bacterium, produces an unknown carboxylate-type siderophore named cupriabactin to overcome iron limitation. Using genome mining, targeted mutagenesis, and biochemical analysis, we discovered an operon containing six open reading frames (cubA–F) in the C. necator JMP134 genome that encodes proteins required for the biosynthesis and uptake of cupriabactin. As the dominant siderophore of C. necator JMP134, cupriabactin promotes the growth of C. necator JMP134 under iron-limited conditions via enhanced ferric iron uptake. Furthermore, we demonstrated that the iron concentration-dependent expression of the cub operon is mediated by the ferric uptake regulator (Fur). Physiological analyses revealed that the cupriabactin-mediated iron acquisition system influences swimming motility, biofilm formation, and resistance to oxidative and aromatic compound stress in C. necator JMP134. In conclusion, we identified a carboxylate-type siderophore named cupriabactin, which plays important roles in iron scavenging, bacterial motility, biofilm formation, and stress resistance. IMPORTANCE Since siderophores have been widely exploited for agricultural, environmental, and medical applications, the identification and characterization of new siderophores from different habitats and organisms will have great beneficial applications. Here, we identified a novel siderophore-producing gene cluster in C. necator JMP134. This gene cluster produces a previously unknown carboxylate siderophore, cupriabactin. Physiological analyses revealed that the cupriabactin-mediated iron acquisition system influences swimming motility, biofilm formation, and oxidative stress resistance. Most notably, this system also plays important roles in increasing the resistance of C. necator JMP134 to stress caused by aromatic compounds, which provide a promising strategy to engineer more efficient approaches to degrade aromatic pollutants.

A novel integrated sulfur fixed-film activated sludge in SBR system (IS0FAS-SBR) was proposed to treat the low C/N ratio municipal wastewater. The effluent total inorganic nitrogen (TIN) and PO43--P decreased from 17 mg/L and 3.5 mg/L to 8.5 mg/L and 0.5 mg/L, and higher nitrogen removal efficiency was contributed by the autotrophic denitrification. Microbial response characteristics showed that catalase (CAT), reduced nicotinamide adenine dinucleotide (NADH) and extracellular polymeric substance (EPS) alleviated the oxidative stress of sulfur carrier to maintain cell activity, while metabolic activity analysis indicated that the electron transfer rate was enhanced to improve mixotrophic denitrification efficiency. Meanwhile, the increased key enzyme activities further facilitated nitrogen removal and sulfur oxidation process. Additionally, the microbial community, functional proteins and genes revealed a niche equilibrium of C, N, S metabolic bacteria. Sulfur autotrophic in-situ coupled SBR system enlarged a promising strategy for treatment of low C/N ratio municipal wastewater.

BackgroundSoil bacteria typically thrive in water-limited habitats that cause an inherent matric stress to the cognate cells. Matric stress gives rise to accumulation of intracellular reactive oxygen species (ROS), which in turn may induce oxidative stress, and even promote mutagenesis. However, little is known about the impact of ROS induced by water limitation on bacteria performing important processes as pollutant biodegradation in the environment. We have rigorously examined the physiological consequences of the rise of intracellular ROS caused by matric stress for the toluene- and xylene-degrading soil bacterium Pseudomonas putida mt-2.MethodsFor the current experiments, controlled matric potential stress was delivered to P. putida cells by addition of polyethylene glycol to liquid cultures, and ROS formation in individual cells monitored by a specific dye. The physiological response to ROS was then quantified by both RT-qPCR of RNA transcripts from genes accredited as proxies of oxidative stress and the SOS response along with cognate transcriptional GFP fusions to the promoters of the same genes.ResultsExtensive matric stress at −1.5 MPa clearly increased intracellular accumulation of ROS. The expression of the two major oxidative defense genes katA and ahpC, as well as the hydroperoxide resistance gene osmC, was induced under matric stress. Different induction profiles of the reporters were related to the severity of the stress. To determine if matric stress lead to induction of the SOS-response, we constructed a DNA damage-inducible bioreporter based on the LexA-controlled phage promoter PPP3901. According to bioreporter analysis, this gene was expressed during extensive matric stress. Despite this DNA-damage mediated gene induction, we observed no increase in the mutation frequency as monitored by emergence of rifampicin-resistant colonies.ConclusionsUnder conditions of extensive matric stress, we observed a direct link between matric stress, ROS formation, induction of ROS-detoxifying functions and (partial) activation of the SOS system. However, such a stress-response regime did not translate into a general DNA mutagenesis status. Taken together, the data suggest that P. putida mt-2 can cope with this archetypal environmental stress while preserving genome stability, a quality that strengthens the status of this bacterium for biotechnological purposes.

No abstract available

Nanomaterials can empower microbial-based chemical production or pollutant removal, e.g., nano zero-valent iron (nZVI) as an electron source to enhance microbial reducing pollutants. Constructing bio-nano interfaces is critical for bio-nano system operation, but low interfacial compatibility due to nanotoxicity challenges the system performance. Inspired by microorganisms’ resistance to nanotoxicity by secreting extracellular polymeric substances (EPS), which can act as electron shuttling media, we design a highly compatible bio-nano interface by modifying nZVI with EPS, markedly improving the performance of a bio-nano system consisting of nZVI and bacteria. EPS modification reduced membrane damage and oxidative stress induced by nZVI. Moreover, EPS alleviated nZVI agglomeration and probably reduced bacterial rejection of nZVI by wrapping camouflage, contributing to the bio-nano interface formation, thereby facilitating nZVI to provide electrons for bacterial reducing pollutant via membrane-anchoring cytochrome c. This work provides a strategy for designing a highly biocompatible interface to construct robust and efficient bio-nano systems for environmental implication.

Chromate has become an environmental pollutant present in different ecosystems due to its use in industry. Bacteria have evolved to resist stress produced by chromate. Among chromate-resistance mechanisms we can list Reactive Oxygen Species detoxification systems. CmeSOD (ChrC) protein from Cupriavidus metallidurans CH34 is a superoxide dismutase that mitigate oxidative stress caused by chromate. Cme-SOD protein belongs to Fe and Mn-dependent SOD family (pfam02777). The objective of this study was to analyze the threedimensional structure of the Cme-SOD protein, for which monomer and tetramer models of the enzyme were built. In the monomer model it was observed that Cme-SOD has a characteristic two-domain structure from iron-dependent SOD, additionally, Cme-SOD has an iron-binding site formed by conserved residues H26 and H75 in the Nterminal domain, and D157 and H161 in the domain Cterminal domain. It was show that chromate stress response SODs have a non-conserved residues in the active site (R37, N59, S71, D143 and Y164). These findings suggest the presence of a novel active site in this family of enzymes.

Microbiological degradation is often considered as an important strategy to reduce the risks of polybrominated diphenyl ethers (PBDEs), which are environmentally widespread and harmful to human health and wildlife. With the well-identified aerobic bacteria, i.e. B. xenovorans LB400, the biodegradation of 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) occurred efficiently in conformity to the first-order kinetics and showed the strong dependence on initial concentration of pollutant and bioavailability regulation by biosurfactant. The mild increase of initial concentration of BDE-47 would enhance biodegradation whereas the excessive increase failed due to the oxidative stress or cytotoxicity to bacteria. Rather than the bacterial extracellular adsorption that was bioactively-mediated in thermodynamics, the intracellular accumulations at different time gradients showed the negative correlation with biodegradation efficiency of BDE-47. The spontaneous biodegradation of pollutant should be sourced from the gradual reduction of intracellular accumulation. Though the improved bioavailability of BDE-47 by sucrose fatty acid ester (SFAE) hardly altered the extracellular adsorption, the bacterial intracellular accumulation was indicated to increase continuously with used amount of biosurfactant and then decrease for the cellular morphological damage, and interestingly it appeared to be temporary reservoir for prompt delivery to biodegradation in light of the opposite variation tendency with time.

Co-contamination of metals and organic pollutants is a global problem as metals interfere with the metabolism of complex organics by bacteria. Based on a prior observation that metal tolerance was altered by the sole carbon source being used for growth, we sought to understand how metal toxicity specifically affects bacteria using an organic pollutant as their sole carbon source. To this end metabolomics was used to compare cultures of Pseudomonas pseudoalcaligenes KF707 grown on either biphenyl (Bp) or succinate (Sc) as the sole carbon source in the presence of either aluminum (Al) or copper (Cu). Using multivariate statistical analysis it was found that the metals caused perturbations to more cellular processes in the cultures grown on Bp than those grown on Sc. Al induced many changes that were indicative of increased oxidative stress as metabolites involved in DNA damage and protection, the Krebs cycle and anti-oxidant production were altered. Cu also caused metabolic changes that were indicative of similar stress, as well as appearing to disrupt other key enzymes such as fumarase. Additionally, both metals caused the accumulation of Bp degradation intermediates indicating that they interfered with Bp metabolism. Together these results provide a basic understanding of how metal toxicity specifically affects bacteria at a biochemical level during the degradation of an organic pollutant and implicate the catabolism of this carbon source as a major factor that exacerbates metal toxicity.

No abstract available

No abstract available

Silver and copper nanoparticles (AgNPs and CuNPs) coated with stabilizing moieties induce oxidative stress in both bacteria and mammalian cells. Effective antibacterial agents that can overcome existing mechanisms of antibacterial resistance will greatly improve biomedical interventions. In this study, we analyzed the effect of nanoparticle-induced stress. Escherichia coli and normal human bronchial epithelial (BEAS-2B) cells were selected for this study. The nanoparticle constructs tested showed low toxicity to mammalian cells except for the polyvinylpyrrolidone-surface-stabilized copper nanoparticles. In fact, both types of copper nanoparticles used in this study induced higher levels of reactive oxygen species than the surface-stabilized silver nanoparticles. In contrast to mammalian cells, the surface-stabilized silver and copper nanoparticles showed varying levels of toxicity to bacteria cells. These data are expected to aid in bridging the knowledge gap in differential toxicities of silver and copper nanoparticles against bacteria and mammalian cells and will also improve infection interventions.

Ever since the “great oxidation event,” Earth’s cellular life forms had to cope with the danger of reactive oxygen species (ROS) affecting the integrity of biomolecules and hampering cellular metabolism circuits. Consequently, increasing ROS levels in the biosphere represented growing stress levels and thus shaped the evolution of species. Whether the ROS were produced endogenously or exogenously, different systems evolved to remove the ROS and repair the damage they inflicted. If ROS outweigh the cell’s capacity to remove the threat, we speak of oxidative stress. The injuries through oxidative stress in cells are diverse. This article reviews the damage oxidative stress imposes on the different steps of the central dogma of molecular biology in bacteria, focusing in particular on the RNA machines involved in transcription and translation.

Soil acidification is causing more and more attention, not only because of the harm of acidification itself, but also the greater harm to bacteria brought by some pollutants under acidic condition. Therefore, the toxicities of two typical soil pollutants (perfluorooctane sulfonate (PFOS) and chromium (Cr(VI)) to growth and metabolisms of soil bacteria (Bacillus subtilis as modol) were investigated. Under acidic condition of pH = 5, Cr(VI), PFOS and PFOS + Cr(VI) show stronge inhibition to bacteria growth up to 24.3%, 42.3%, 41.6%, respectively, and this inhibition was about 2-3 times of that at pH = 7. Moreover, acid stress reduces the metabolism of bacteria, while PFOS and Cr(VI) pollution futher strengthens this metabolic inhibition involving oxidative stress and cell permeability. The activities of dehydrogenase (DHA) and electron transport system (ETS) at pH = 5 exposed to Cr(VI), PFOS and combined PFOS + Cr(VI) was 21.5%, 16.9%, 23.2% and 8.9%, 32.2%, 19.1% lower than the control, respectively. However, the relative activity of DHA and ETS at pH = 7 are 5-8 and 2-13 times of that at pH = 5, respectively. Isoelectric point, cell surface hydrophobicity and molecular simulation analysis show that the corresponding mechanism is that acidic conditions enhance the interaction between bacteria and PFOS/Cr(VI) through hydrogen bonding, hydrophobic and electrostatic interactions. The results can guide the remediation of acid soil pollution, and provide a reference for the combined toxicity evaluation of heavy metals and micro-pollutants in acid soil.

Copper(II) oxide nanoparticles (CuO NPs) are used in different industries and agriculture, thus leading to their release to the environment, which raises concerns about their ecotoxicity and biosafety. The main toxicity mechanism of nanometals is oxidative stress as a result of the formation of reactive oxygen species caused by metal ions released from nanoparticles. Bacterial biofilms are more resistant to physical and chemical factors than are planktonic cells due to the extracellular polymeric matrix (EPM), which performs a protective function. Hydrocarbon-oxidizing bacteria of the genus Rhodococcus, well-known biodegraders of toxic organic pollutants and bioremediation agents, are capable of producing biofilms, which, as we proposed, are more resistant to metal nanoparticles, while the particular adaptation mechanisms have not yet been clarified. In this study, we study the adaptation mechanisms of Rhodococcus rhodochrous IEGM 1363 biofilms to CuO NPs in a wide range of concentrations (0.001-0.1 g/L), including morphological and ultrastructural cell alterations. The results obtained on the long-term dynamics (≤72 h) and localization of EPM structural components, in particular, lipids, polysaccharides, and proteins, indicated their important role in the complex adaptive response of alkanotrophic Rhodococcus to oxidative stress caused by copper nanooxide. The observed changes in the ultrastructure and element composition included binding of CuO nanoparticles by the cell wall to prevent their penetration inside cells and intracellular accumulation of potassium, magnesium, phosphorus, and sulfur in electron-dense inclusions, which may be associated with a metabolic stress reaction. Understanding the mechanisms of interaction between nanometals and Rhodococcus biofilms will contribute to the development of biocatalysts based on immobilized bacterial cells and bioremediation methods.

No abstract available

ABSTRACT Bacterial persistence increases therapy duration, disease relapse, and antibiotic resistance. Mechanisms underlying persistence and feasible ways to rapidly eliminate persister cells are largely unknown. The present work examined genetic and environmental perturbations to identify anti-death events occurring in Escherichia coli persister and phenotypically tolerant cells. The quiescent status of hipA7 and metG2 persister cells, which were protected from killing by multiple antibiotics, was insensitive to the presence/absence of exogenous nutrients. In contrast, stationary-phase and nutrient-starved wild-type cultures, which displayed tolerance rather than the subpopulation status of persistence, were readily killed by ciprofloxacin upon restoration of nutrients, thereby indicating that tolerance was phenotypic. Both persistent and tolerant cells suppressed accumulation of reactive oxygen species (ROS), DNA breakage, and global metabolic activity. Restoration of nutrients to stationary-phase cultures restored these three processes for phenotypically tolerant cells but not for persister cells. Cultures of high-frequency-persistent hipA7 and metG2 mutants and low-frequency-persistent wild-type cells were rapidly sterilized by ROS-independent, synergistic membrane disruption using aminoglycoside-polymyxin combinations; rapid eradication occurred at clinically achievable concentrations for both antibiotics. The aminoglycoside-polymyxin combination also killed environmentally tolerant cells but more slowly. The combination killed both laboratory and clinical isolates of gram-negative bacteria, an E. coli ptsI mutant that is pan-tolerant to diverse antibiotics and disinfectants, and E. coli cells in a biofilm model. Moderate lethality was observed with the gram-positive bacterium Staphylococcus aureus. The work indicates that suppression of ROS accumulation is a common feature of persistence and phenotypic tolerance, and it emphasizes ROS-independent strategies for controlling quiescent bacterial populations. IMPORTANCE The report generalizes the concept that persistence and tolerance involve suppression of toxic metabolites (reactive oxygen species [ROS]). The work also shows that an environmental perturbation (nutrient deprivation) leads to antibiotic tolerance rather than persistence, thereby raising questions about the classification of other environmental perturbations. The synergistic action of multiple aminoglycoside species with polymyxins opens many treatment options. Lethality with biofilms and with S. aureus may extend polymyxin-based therapies beyond planktonic, gram-negative bacteria, and the ROS independence of the combination may allow antioxidant mitigation of drug toxicity. Overall, the work advances our knowledge of persistent and tolerant bacterial pathogens and our efforts to eradicate them. The report generalizes the concept that persistence and tolerance involve suppression of toxic metabolites (reactive oxygen species [ROS]). The work also shows that an environmental perturbation (nutrient deprivation) leads to antibiotic tolerance rather than persistence, thereby raising questions about the classification of other environmental perturbations. The synergistic action of multiple aminoglycoside species with polymyxins opens many treatment options. Lethality with biofilms and with S. aureus may extend polymyxin-based therapies beyond planktonic, gram-negative bacteria, and the ROS independence of the combination may allow antioxidant mitigation of drug toxicity. Overall, the work advances our knowledge of persistent and tolerant bacterial pathogens and our efforts to eradicate them.

The antimicrobial activity of the natural compounds from plant and food have well discovered since the interest on the beneficial effect of the natural compounds was risen. Quercetin, a flavonoid derived from vegetables, including onions, red leaf lettuces and cherries has been studied for diverse biological characteristics as anti-cancer and anti-microbial activities. The aim of current study is to investigate the specific antibacterial modes of action of quercetin against Escherichia coli. Quercetin decreased the E. coli cell viability and induced the severe damages (oxidative stress, DNA fragmentation) leading to cell death. Reactive oxygen species (ROS) generation was observed during the process, which we confirmed that oxidative stress was the key action of antibacterial activity of quercetin exerting its influence potently. Based on the results of Annexin V and Caspace FITC-VAD-FMK assay, the oxidative damage in E. coli has led to the bacterial apoptosis-like death in E. coli. To sum up, the contribution of ROS generation exerts crucial impact in antibacterial activity of quercetin.

The presence of excessive residual Cu(II), a high-risk heavy metal with potential toxicity and biomagnification property, substantially impede the value-added utilization of anaerobic digestion effluent (ADE). This study adapted indigenous bacterial consortium (IBCs) to eliminate Cu(II) from ADE, and their performances and resistance mechanisms against Cu(II) were analyzed. Results demonstrated that when the Cu(II) exposure concentration exceeded 7.5 mg/L, the biomass of IBCs decreased significantly, cells produced a substantial amount of ROS and EPS, at which time the intracellular Cu(II) content gradually decreased, while Cu(II) accumulation within the EPS substantially increased. The combined features of a high PN/PS ratio, a reversed Zeta potential gradient, and abundant functional groups within EPS collectively render EPS a primary diffusion barrier against Cu(II) toxicity. Mutual physiological and metagenomics analyses reveal that EPS synthesis and secretion, efflux, DNA repair along with coordination between each other were the primary resistance mechanisms of IBCs against Cu(II) toxicity. Furthermore, IBCs exhibited enhanced resistance by enriching bacteria carrying relevant resistance genes. Continuous pretreatment of actual ADE with IBCs at a 10-day hydraulic retention time (HRT) efficiently eliminated Cu(II) concentration from 5.01 mg/L to ∼0.68 mg/L by day 2. This elimination remained stable for the following 8 days of operation, further validated their good Cu(II) elimination stability. Notably, supplementing IBCs with 200 mg/L polymerized ferrous sulfate significantly enhanced their settling performance. By elucidating the intricate interplay of Cu(II) toxicity and IBC resistance mechanisms, this study provides a theoretical foundation for eliminating heavy metal barriers in ADE treatment.

Microbial spoilage poses significant challenges to food safety, necessitating innovative antimicrobial strategies. This study develops a redox-driven photodynamic inactivation (PDI) system, integrating vitamin C (VC) with vitamin B2 (VB2) to modulate reactive oxygen species (ROS) composition and enhance bactericidal efficiency. The VB2/VC interaction selectively enhances hydrogen peroxide (H2O2) accumulation under illumination, which then reacts with VC post-irradiation to generate highly cytotoxic OH, ensuring >99.999 % eradication of Pseudomonas fragi even after illumination ceases. Mechanistic analyses using molecular spectroscopy, physicochemical membrane assessments, and metabolic profiling reveal a two-stage bactericidal mechanism: ROS initially induce membrane conformational changes and disrupt electrochemical stability, followed by oxidative stress and metabolic collapse, ultimately leading to bacterial lysis. Importantly, the system significantly extends the shelf life of chilled beef by delaying microbial growth and preserving physicochemical properties. This study provides new insights into redox-mediated antibacterial mechanisms and offers a promising, non-thermal strategy for improving food preservation and safety.

Microalgal-bacterial granular sludge (MBGS) enables carbon-neutral wastewater treatment by replacing aeration with photosynthetic oxygen. However, excessive light can induce dissolved oxygen (DO) supersaturation and triggering oxidative stress. This study investigated the effects of lighting mode (continuous vs. intermittent) and light intensity (400 and 800 μmol/m2/s) on MBGS performance over 96 days. At both light intensities, continuous light caused severe DO accumulation (>25 mg O2/L), elevated reactive oxygen species (ROS), and reduced nutrient removal. Intermittent light effectively regulated DO, alleviated ROS stress, enhanced antioxidative enzyme activity, and restored microbial function. Under intermittent light, NH4-N, TN, and PO4-P removal efficiencies reached 99.2 %, 81.5 %, and 94.2 % (400 μmol/m2/s), and 89.7 %, 69.9 %, and 91.5 % (800 μmol/m2/s). Functional genera such as Dechloromonas, Pseudoxanthomonas and Pseudomonas were enriched under intermittent light mode. These results demonstrate that intermittent light is a feasible strategy to mitigate photo-oxygen stress and enhance nutrient removal in aeration-free MBGS systems.

Copper is a metal historically used to prevent infections. One of the most relevant challenges in modern society are infectious disease outbreaks, where copper-based technologies can play a significant role. Currently, copper nanoparticles and surfaces are the most common antimicrobial copper-based technologies. Despite the widespread use of copper on nanoparticles and surfaces, the toxicity mechanism(s) explaining their unique antimicrobial properties are not entirely known. In general, toxicity effects described in bacteria and fungi involve the rupture of membranes, accumulation of ions inside the cell, protein inactivation, and DNA damage. A few studies have associated Cu-toxicity with ROS production and genetic material degradation in viruses. Therefore, understanding the mechanisms of the toxicity of copper nanoparticles and surfaces will contribute to developing and implementing efficient antimicrobial technologies to combat old and new infectious agents that can lead to disease outbreaks such as COVID-19. This review summarizes the current knowledge regarding the microbial toxicity of copper nanoparticles and surfaces and the gaps in this knowledge. In addition, we discuss potential applications derived from discovering new elements of copper toxicity, such as using different molecules or modifications to potentiate toxicity or antimicrobial specificity.

No abstract available

Chronic infected wounds suffer from impaired tissue healing due to bacterial biofilm formation, an imbalanced inflammatory microenvironment, excessive accumulation of reactive oxygen species (ROS) and pyroptosis triggered by GSDMD activation. Herein, a multifunctional soluble microneedle system (ACBP@MN) that integrates ultrathin Au/Cu nanosheets loaded with the traditional Chinese medicine monomer Bergapten (BP) is developed. This system enables bidirectional ROS regulation, synergizing catalytic ROS generation with antioxidant defense activation and pyroptosis pathway modulation to break the infection-inflammation-oxidative damage cycle. Our results confirmed that in a S. aureus-infected murine wound model, ACBP@MN showed superior antibacterial, anti-inflammatory, angiogenic, and regenerative outcomes, with excellent biosafety. During the early infection phase, ACBP@MN exerts potent bactericidal effects via peroxidase-like activity and glutathione depletion. RNA sequencing revealed that it also disrupts bacterial biofilm formation and key metabolic pathways, including the TCA cycle and BCAA metabolism. At the inflammatory stage, ACBP@MN reduces oxidative stress and persistent inflammation by enhancing the activities of catalase and superoxide dismutase enzymes and upregulating the Nrf2/HO-1 pathway. Subsequently, Nrf2 activation indirectly inhibits the NF-κB pathway, leading to suppressed NLRP3 inflammasome activation and prevention of GSDMD-mediated pyroptosis. In conclusion, this study proposes an innovative strategy for chronic infected wound management through the rational design of multifunctional composite microneedle systems.

The emergence of multi‐drug resistant (MDR) pathogens is a major public health concern, posing a substantial global economic burden. Photothermal therapy (PTT) at mild temperature presents a promising alternative to traditional antibiotics due to its biological safety and ability to circumvent drug resistance. However, the efficacy of mild PTT is limited by bacterial thermotolerance. Herein, a nanocomposite, BP@Mn‐NC, comprising black phosphorus nanosheets and a manganese‐based nanozyme (Mn‐NZ) is developed, which possesses both photothermal and catalytic properties. Mn‐NZ imparts glucose oxidase‐ and peroxidase‐like properties to BP@Mn‐NC, generating reactive oxygen species (ROS) that induce lipid peroxidation and malondialdehyde accumulation across the bacterial cell membrane. This process disrupts unprotected respiratory chain complexes exposed on the bacterial cell membrane, leading to a reduction in the intracellular adenosine triphosphate (ATP) content. Consequently, mild PTT mediated by BP@Mn‐NC effectively eliminates MDR infections by specifically impairing bacterial thermotolerance because of the dependence of bacterial heat shock proteins (HSPs) on ATP molecules for their proper functioning. This study paves the way for the development of a novel photothermal strategy to eradicate MDR pathogens, which targets bacterial HSPs through ROS‐mediated inhibition of bacterial respiratory chain activity.

No abstract available

The contamination of drinking water by microbes is a critical health concern, underscoring the need for safe, reliable, and efficient methods to treat pathogenic microorganisms. While most sterilization materials are available in powder form, this presents safety risks and challenges in recycling. Herein, this study reports the preparation of an innovative copper oxide supported silver monolithic nanoarray mesh with abundant oxygen vacancies (Ag/CuO-VO) by laser ablation. The instantaneous high temperature caused by laser ablation preserves the material's original structure while generating oxygen vacancies on the CuO surface. The Ag/CuO-VO mesh demonstrated a remarkable ability to inactivate over 99% of Escherichia coli (E. Coli) within 20 min. The oxygen vacancies in the Ag/CuO-VO enhance interactions between oxygen species and the Ag/CuO-VO, leading to the accumulation of large amounts of reactive oxygen species (ROS). The generated ROS effectively disrupt both layers of the bacterial cell wall - the peptidoglycan and the phospholipid - as confirmed by Fourier Transform Infrared (FTIR) spectroscopy, culminating in cell death. This research presents a monolithic material capable of inactivating pathogenic microorganisms efficiently, offering a significant advancement in water sterilization technology.

The wide application of zinc oxide (ZnO) nanoparticles increases the possibility of their release into the agricultural environment. This study aimed to investigate the influence of ZnO nanoparticles on the composting process, because composting is the main means to dispose of agricultural organic waste. A lab-scale experiment was conducted to investigate the effects of different concentrations of ZnO nanoparticles (0.1, 1, and 10 mg/kg) on the physicochemical properties (temperature, pH, and seed germination index), and the bacterial community components and structure, of the compost. The results show that ZnO nanoparticle treatments had a low influence on the temperature and seed germination index, but that they decreased the pH of the compost. For the bacterial community, no significant differences were detected in terms of the alpha diversity, but the bacterial community structure and components were changed by exposure to ZnO nanoparticles. The largest variations in the bacterial community were found at the hyperthermal stage. In particular, the genera affiliated with Firmicutes and Bacteroidetes were changed to a large extent. The 0.1 mg/kg ZnO nanoparticles treatment increased the relative abundance of Cohnella , whereas the 1 mg/kg and 10 mg/kg treatments enhanced the proportions of Weissella , Bacillus , and Enterococcus , and decreased the relative abundance of certain genera belonging to Bacteroidetes. Our investigation indicate that ZnO nanoparticles influenced some functional guilds in microbial communities as well as the physicochemical properties of the compost, which is conducive to the evaluation of environmental responses to ZnO nanoparticle exposure.

近年来, 病原体引起的流行病频发, 对含能杀菌剂提出了迫切需求; 它们可通过爆炸性反应快速地大面积抛洒以单质碘为主的高效广谱杀菌物质, 但其高碘含量与高爆性能难以同时兼得. 在此, 我们报道了一类新型含能杀菌剂——多碘分子钙钛矿: (H_2dabco)M(IO_4)_3 (dabco= 1,4-二氮杂双环[2.2.2]辛烷, M = Na^+/K^+/Rb^+/NH_4^+分别对应DAI-1/2/3/4)和(H_2dabco)Na(H_4IO_6)_3 (DAI-X1). 这些化合物具有立方钙钛矿结构, 不仅具有高碘含量(4 9–5 4 w t %), 而且具有较高的爆速(6.331–6.558 km s^−1)和爆压(30.69–30.88 GPa). 特别地, DAI-4具有高达54.0 wt%的碘含量, 以及6.558 km s^−1的爆速. 激光扫描共聚焦显微镜观察和标准微量肉汤稀释法实验表明, DAI-4的爆炸产物对细菌(大肠杆菌、金黄色葡萄球菌和铜绿假单胞菌)具有广谱杀菌性. 这类基于高碘酸根的分子钙钛矿具有易于放大合成、低成本、高爆轰性能和高碘含量的优点, 是极具潜力的新型含能杀菌剂. Epidemics caused by pathogens in recent years have created an urgent need for energetic biocidal agents with the capacity of detonation and releasing bactericides. Herein we present a new type of energetic biocidal agents based on a series of iodine-rich molecular perovskites, (H_2dabco)M(IO_4)_3 (dabco = 1,4-diazabicyclo[2.2.2]octane, M = Na^+/K^+/Rb^+/NH_4^+ for DAI-1/2/3/4) and (H_2dabco)Na(H_4IO_6)_3 (DAI-X1). These compounds possess a cubic perovskite structure, and notably have not only high iodine contents (49–54 wt%), but also high performance in detonation velocity (6.331–6.558 km s^−1) and detonation pressure (30.69–30.88 GPa). In particular, DAI-4 has a very high iodine content of 54.0 wt% and simultaneously an exceptional detonation velocity up to 6.558 km s^−1. As disclosed by laser scanning confocal microscopy observation and a standard micro-broth dilution method, the detonation products of DAI-4 exhibit a broad-spectrum bactericidal effect against bacteria ( E. coli, S. aureus , and P. aeruginosa ). The advantages of easy scale-up synthesis, low cost, high detonation performance, and high iodine contents enable these periodate-based molecular perovskites to be highly promising candidates for energetic biocidal agents.

Chemical dispersants are widely used in emergency response of marine oil spills. However, their genotoxicity information is relatively scarce. This research aimed to evaluate the environmental safety of chemical dispersants used for rapid removal and cleaning up of marine oil spills. We used luminescent bacteria test (LBT) based on Acinetobacter sp. RecA combined with fish exposure experiment based on marine medaka ( Oryzias melastigma ) to detect the genotoxicity of 6 chemical dispersants. In LBT, the 500 mg / L and 1 000 mg / L of chemical dispersant HLD-501 exhibited genotoxicity of 0.039 mg/L and 0.032 mg/L of mitomycin C (MMC), respectively. In addition, the DNA damage ratio of O. melastigma by the 6 chemical dispersants in the comet assay was in the order of concentrate type RS-II > concentrate type RS-I > conventional type HLD-501 > conventional type Fuken-2 > conventional type RS-I > conventional type Weipu. However, HLD-501 resulted in the most serious DNA damage (level 3), being the most genotoxic among the 6 dispersants. The result of these two methods for genotoxicity detection fitted well with each other. This study could provide a useful reference for environmental safety evaluation of the chemical dispersants used in cleaning up of the marine oil spills.

After the Sinopec pipeline explosion on Nov. 22, 2013 at Huangdao, China, local beaches and sea water at Jiaozhou Bay was polluted by crude oil to different degrees. This study investigated the ecological effect of petroleum hydrocarbons in seawater on marine organisms with a rapid genotoxicity detection method based on the luminescent bacteria Acinetobacter sp. RecA. We collected seawater samples from five sites 1 km to 15 km away from the oil leakage point during a time course of 90 days. The chemical composition of petroleum hydrocarbons in the seawater samples were analyzed by GC-MS. Meanwhile, the genotoxicity of each sample was determined by Acinetobacter sp. RecA using mitomycin C (MMC) as reference standard toxicant. The results showed that the petroleum hydrocarbon contents of 3 samples from sites S1, S2, and S3 within 1 km from the oil leakage point were from 0.55 mg/L to 1.04 mg/L. The corresponding genotoxicity was equivalent to 0.60 mg/L to 1.78 mg/L of MMC. The genotoxicity level decreased as the petroleum hydrocarbon content gradually decreased to < 0.02 mg/L over time. The samples from sites S4 and S5 which were over 5 km away from the oil leakage point had low petroleum hydrocarbons content (< 0.02 mg/L) and exhibited low or no genotoxicity during the 90 days. The results suggested that as a whole cell biosensor, luminescent bacteria Acinetobacter sp. RecA can quickly and accurately detect genotoxicity of contaminated sea water. This method has great potential in providing technical support after marine oil spill. It can also be used to monitor the dynamics for environmental risk assessment of marine pollution.

No abstract available

Coconut milk, the crude aqueous extract of the scraped endosperm of the nutty fruit of Cocos nucifera, is an edible plant product used as a food or food additive. Previous studies have reported that it contains, among other biomolecules, phenolic compounds that can act as antioxidants against oxidative stress caused by Reactive Oxygen Species. Pretreatment with phenolic compounds from coconut milk has been previously reported to augment antioxidant protection in the eukaryote Saccharomyces cerevisiae and other organisms. This study aimed to determine whether the phenolic extract of coconut milk offers any antioxidant protection against selected bacteria subjected to oxidative stress. It was observed that the phenolic extract of coconut milk, once absorbed into cells, conferred significant protection against induced oxidative stress in both Escherichia coli and Lactobacillus spp. This protective effect was demonstrated by a reduction in lipid peroxidation (p<0.05; n=3) and by a significant increase in cell survival following oxidative challenge (p<0.05; n=3). These findings demonstrated that the phenolic extract of coconut milk provides both general and specific antioxidant protection to beneficial bacteria, offering insights into potential interactions between dietary coconut products and gut microbial resilience.

Heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria possess considerable potential for treating high-ammonia wastewater; however, their denitrification characteristics and response mechanisms under microplastics (MPs) stress remain inadequately understood. This study systematically investigated the effects of typical MPs on the denitrification performance of HN-AD bacteria strain TAC-1 through batch experiments, metatranscriptomic and ultrastructural analysis. The findings demonstrated that hydrophobic nature of polyvinyl chloride (PVC) disrupted the intermolecular interactions among lipid molecules, reducing cell membrane density and forming permeable channels. This structural damage decreased the expression of the sulfate/sulfonate transport system (cysW/cysP/cysU/cysA), impairing bacterial protein synthesis. In response to survival pressure, the strain activated an immune evasion mechanism by upregulating the expression of fimbriae synthesis genes (fimA and fimD). ompared to PVC, polyethylene (PE), due to its high chemical stability, induced the disorganization of membrane lipids without significantly compromising membrane integrity. Notably, 100 nm PE particles enhanced the iron acquisition capability of the strain, leading to increases of 24.63 % in ammonia nitrogen (NH4+-N) removal rates. However, this promotional effect declined following prolonged exposure (>6 days) due to the accumulation of intracellular toxic substances. The cationic surface characteristics of polystyrene (PS) induced severe oxidative stress, leading to the most pronounced structural damage to the membrane. Although PS impaired denitrification efficiency by disrupting membrane integrity, it maintained NH4+-N conversion capacity through compensatory metabolic reorganization mediated by the glutamine synthetase and glutamate dehydrogenase pathways. These findings provide a theoretical foundation for enhancing the anti-interference resilience of biological wastewater treatment systems.

Microbial ferroptosis has been proved to combat drug-resistant pathogens, but whether this pattern can be applied to the prevention and control of Escherichia coli remains to be further explored. In this study, ferrous gluconate (FeGlu) showed remarkable efficacy in killing E. coli MG1655 with a mortality rate exceeding 99.9%, as well as enterotoxigenic E. coli H10407 (ETEC H10407) and enterohemorrhagic E. coli O157:H7 (EHEC O157:H7). Bacteria death was instigated by the infiltration of Fe2+, accompanied by a burst of intracellular reactive oxygen species (ROS) and lipid peroxidation. Notably, mitigating lipid peroxidation failed to alleviate death of E. coli. Further findings confirmed that FeGlu induced DNA damage, and ΔrecA mutant showed more sensitive, implicating that DNA damage was involved in the death of E. coli. The direct interaction of Fe2+ with DNA was demonstrated by fluorescent staining, gel electrophoresis, and circular dichroism (CD). Moreover, proteomic analysis unveiled 50 differentially expressed proteins (DEPs), including 18 significantly down-regulated proteins and 32 significantly up-regulated proteins. Among them, the down-regulation of SOS-responsive transcriptional suppressor LexA indicated DNA damage induced severely by FeGlu. Furthermore, FeGlu influenced pathways such as fatty acid metabolism (FadB, FadE), iron-sulfur cluster assembly (IscA, IscU, YadR), iron binding, and DNA-binding transcription, along with α-linolenic acid metabolism, fatty acid degradation, and pyruvate metabolism. These pathways were related to FeGlu stress, including lipid peroxidation and DNA damage. In summary, FeGlu facilitated ferroptosis in E. coli through mechanisms involving lipid peroxidation and DNA damage, which presents a new strategy for the development of innovative antimicrobial strategies targeting E. coli infections.

The interrelation between the composition of components of five samples of natural water and state indices for the lipid peroxidation regulatory system in a model system based on the natural phospholipids was explored and involvement of natural phospholipids in the formation of the toxicity of the natural water was also studied. It is shown that the presence of N- and P-containing compounds in natural water samples leads to inhibition of the processes relevant to lecithin autooxidation and luminescence intensity of luminous bacteria, has a significant effect on the spontaneous aggregation of lecithin, while an increase in the content of hydrophobic compounds results in a higher negative value of the ξ potential of its particles. High sensitivity of the lipid peroxidation regulatory system to the presence of components even at low concentrations in the natural water makes it a promising tool to test the effect of natural water on biological objects. Mathematical processing of UV spectra of the natural water samples with the Gauss method can be used as an express test for the analysis of its hydrochemical composition. The effects of natural water components on the state of membranes of biological objects and intracellular processes are confirmed by means of biotesting methods.

The current work deals with a time-dependent study to track the antibacterial action of electrodeposited Cu, Cu-SiC functionally graded coating (FGC) against Escherichia coli NCIM 2931 (Gram-negative) and Bacillus subtilis NCIM 2063 (Gram-positive). After 24 h of incubation, the Cu, Cu-SiC FGC causes 7 Escherichia coli NCIM 2931 and 10 Bacillus subtilis NCIM 2063 log reduction of planktonic cells. The outer membrane permeabilization experiment proves that the intake of excessive Cu ions leads to the damage of bacterial cell membrane followed by lipid degradation. The thiobarbituric acid reactive substances assay reveals that Cu ions released from the surface of Cu, Cu-SiC FGC triggers the oxidative degeneration of phospholipids (most abundant constituent of bacterial cell membrane). This was further cross-verified using atomic absorption spectroscopy. From 0 to 24 h, the bacterial morphology is characterized using transmission electron microscope and scanning electron microscope which shows the cytoplasmic leakage and cell death. The Cu, Cu-SiC FGC also exhibits hydrophobic surface (contact angle of 144°) which prevents the bacterial adherence to the surface and thus, inhibits them to penetrate into its bulk. The observed results of antibacterial and anti-adhesion properties of Cu, Cu-SiC FGC are compared with single-layered metallic Cu and Cu-SiC nanocomposite coatings. Hence, the electrodeposited Cu, Cu-SiC FGC has the potential to serve as an inexpensive touch surface alternative for the healthcare industries.

Ferroptosis is a new kind of programmed cell death of which occurrence in microorganisms is not clearly verified. The elevated level of reactive oxygen species (ROS) influences cellular metabolisms through highly reactive hydroxyl radical formation under the iron-dependent Fenton reaction. Iron contributes to ROS production and acts as a cofactor for lipoxygenase to catalyze poly unsaturated fatty acid (PUFA) oxidation, exerting oxidative damage in cells. While ferroptosis is known to take place only in mammalian cells, recent studies discovered the possible ferroptosis-like death in few specific microorganisms. Capacity of integrating PUFA into intracellular membrane phospholipid has been considered as a key factor in bacterial or fungal ferroptosis-like death. Vibrio species in bacteria and Saccharomyces cerevisiae in fungi exhibited certain characteristics. Therefore, this review focus on introducing the occurrence of ferroptosis-like death in microorganisms and investigating the mode of action underlying the cells based on contribution of lipid peroxidation and iron-dependent reaction.

No abstract available

This study investigated the bactericidal activity of plasma-activated water (PAW) generated with a remote discharge reactor against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes. PAW-40, -80, and -120, prepared by activating distilled water for 40, 80, and 120 min, respectively, showed inactivation activity against pathogenic bacteria, which increased as the activation time increased due to decrease in pH and increase in oxidation-reduction potential and reactive oxygen/nitrogen species (RONS) of PAW. In addition, Gram-positive bacteria L. monocytogenes showed superior resistance to PAW than Gram-negative bacteria E. coli O157:H7 and S. Typhimurium. Compared with E. coli O157:H7 and S. Typhimurium, L. monocytogens exhibited less cell membrane damage, lipid peroxidation, and intracellular ROS accumulation after PAW treatment, which indicated that L. monocytogenes exhibited greater resistance because the thick cell wall buffered RONS diffusion into the cell. PAW also showed a control effect on the pathogenic bacteria on cherry tomato, and the effect was maintained throughout five repeated applications; thus, proposing high reusability of PAW. The results of this study propose that PAW generated with a remote discharge reactor can be utilized for pathogen control and provides basic data for related research and practical industrial applications.

No abstract available

The chemical composition of the volatile oils from five Anacardiaceae species and their activities against Gram positive and negative bacteria were assessed. The peroxidative damage within bacterial cell membranes was determined through the breakdown product malondialdehyde (MDA). The major constituents in Anacardium humile leaves oil were (E)-caryophyllene (31.0%) and α-pinene (22.0%), and in Anacardium occidentale oil they were (E)-caryophyllene (15.4%) and germacrene-D (11.5%). Volatile oil from Astronium fraxinifolium leaves were dominated by (E)-β-ocimene (44.1%) and α-terpinolene (15.2%), whilst the oil from Myracrodruon urundeuva contained an abundance of δ-3-carene (78.8%). However, Schinus terebinthifolius leaves oil collected in March and July presented different chemical compositions. The oils from all species, except the one from A. occidentale, exhibited varying levels of antibacterial activity against Staphylococcus aureus, Bacillus cereus and Escherichia coli. Oil extracted in July from S. terebinthifolius was more active against all bacterial strains than the corresponding oil extracted in March. The high antibacterial activity of the M. urundeuva oil could be ascribed to its high δ-3-carene content. The amounts of MDA generated within bacterial cells indicate that the volatile oils induce lipid peroxidation. The results suggest that one putative mechanism of antibacterial action of these volatile oils is pro-oxidant damage within bacterial cell membrane explaining in part their preservative properties.

How double-membraned Gram-negative bacteria overcome lipid peroxidation is virtually unknown. Bactericidal antibiotics and superoxide ion stress stimulate the transcription of the Burkholderia cenocepacia bcnA gene that encodes a secreted lipocalin. bcnA gene orthologs are conserved in bacteria and generally linked to a conserved upstream gene encoding a cytochrome b561 membrane protein (herein named lcoA, lipocalin-associated cytochrome oxidase gene). Mutants in bcnA, lcoA, and in a gene encoding a conserved cytoplasmic aldehyde reductase (peroxidative stress-associated aldehyde reductase gene, psrA) display enhanced membrane lipid peroxidation. Compared to wild type, the levels of the peroxidation biomarker malondialdehyde (MDA) increase in the mutants upon exposure to sublethal concentrations of the bactericidal antibiotics polymyxin B and norfloxacin. Microscopy with lipid peroxidation–sensitive fluorescent probes shows that lipid peroxyl radicals accumulate at the bacterial cell poles and septum and peroxidation is associated with a redistribution of anionic phospholipids and reduced antimicrobial resistance in the mutants. We conclude that BcnA, LcoA, and PsrA are components of an evolutionary conserved, hitherto unrecognized peroxidation detoxification system that protects the bacterial cell envelope from lipid peroxyl radicals.

AbstrectBackgroundTo understand whether TLR-4-linked NF-kB activation negatively correlates with lipid peroxidation in colitic animal models, we caused colitis by the treatment with dextran sulfate sodium (DSS) or 2,4,6-trinitrobenzenesulfonic acid (TNBS) to C3H/HeJ (TLR-4-defective) and C3H/HeN (wild type) mice, investigated inflammatory markers, lipid peroxidation, proinflammatory cytokines and TLR-4-linked NF-κB activation, in colon and intestinal bacterial composition in vivo.MethodsOrally administered DSS and intrarectally injected TNBS all caused severe inflammation, manifested by shortened colons in both mice. These agents increased intestinal myeloperoxidase activity and the expression of the proinflammatory cytokines, IL-1β, TNF-α and IL-6, in the colon.ResultsDSS and TNBS induced the protein expression of TLR-4 and activated transcription factor NF-κB. However, these colitic agents did not express TLR-4 in C3H/HeJ mice. Of proinflammatory cytokines, IL-1β was most potently expressed in C3H/HeN mice. IL-1β potently induced NF-κB activation in CaCo-2 cells, but did not induce TLR-4 expression. DSS and TNBS increased lipid peroxide (malondialdehyde) and 4-hydroxy-2-nonenal content in the colon, but reduced glutathione content and superoxide dismutase and catalase activities. These colitic inducers increased the number of Enterobacteriaceae grown in DHL agar plates in both mice, although the number of anaerobes and bifidobacteria grown in GAM and BL agar plates was reduced. E. coli, K. pneumoniae and Proteus mirabilis isolated in DHL agar plates increased lipid peroxidation in liposomes prepared by L-α-phosphatidylcholine, but B. animalis and B. cholerium isolated from BL agar plates inhibited it.DiscussionThese findings suggest that DSS and TNBS may cause colitis by inducing lipid peroxidation and enterobacterial proliferation, which may deteriorate the colitis by regulating proinflammatory cytokines via TLR-4-linked NF-κB activation pathway.

No abstract available

Bacterial biofilms are hotspots for the natural transformation of antibiotic resistance genes (ARGs). Antibiotics and heavy metals at the sub-minimal inhibitory concentrations (sub-MICs) are ubiquitous in water environments, but their impact on the ARG dissemination via natural transformation in biofilms and the biofilm development remains poorly understood. This study found that the individual stressors including tetracycline, sulfamethoxazole, and Zn at the sub-MIC levels, significantly enhanced ARG transformation. Notably, Zn exhibited the most obvious effect, increasing transformation frequencies by up to 4.62-fold in B. subtilis and 6.42-fold in A. baylyi biofilms. Their combined stressors increased the higher ARG transformation compared to the individual. These stressors significantly elevated ARG transformation by stimulating reactive oxygen species generation, increasing membrane permeability, and enhancing polysaccharide production. Meanwhile, the bacterial adaptability in biofilm to stressors was achieved via ARG transformation, and the biofilm growth was increased by 25.4 % in B. subtilis and 49.6 % in A. baylyi, respectively, compared to biofilms without natural transformation. Except for ARG uptake via transformation, the enhanced bacterial adaptability in biofilms to stressors can also be attributed to the expression of the plasmid-borne SOS response-related genes. These findings broaden the understanding of the influence of sub-MIC stressors in ARG dissemination in biofilm.

Vibrio cholerae is a common waterborne pathogen that can cause pandemic cholera in humans. The bacterium with heavy metal-tolerant phenotypes is frequently isolated from aquatic products, however, its tolerance mechanisms remain unclear. In this study, we investigated for the first time the response of such V. cholerae isolates (n = 3) toward the heavy metal (Cd2+, Ni2+, Pb2+, and Zn2+) stresses by comparative secretomic and proteomic analyses. The results showed that sublethal concentrations of the Pb2+ (200 μg/mL), Cd2+ (12.5 μg/mL), and Zn2+ (50 μg/mL) stresses for 2 h significantly decreased the bacterial cell membrane fluidity, but increased cell surface hydrophobicity and inner membrane permeability, whereas the Ni2+ (50 μg/mL) stress increased cell membrane fluidity (p < 0.05). The comparative secretomic and proteomic analysis revealed differentially expressed extracellular and intracellular proteins involved in common metabolic pathways in the V. cholerae isolates to reduce cytotoxicity of the heavy metal stresses, such as biosorption, transportation and effluxing, extracellular sequestration, and intracellular antioxidative defense. Meanwhile, different defensive strategies were also found in the V. cholerae isolates to cope with different heavy metal damage. Remarkably, a number of putative virulence and resistance-associated proteins were produced and/or secreted by the V. cholerae isolates under the heavy metal stresses, suggesting an increased health risk in the aquatic products.

Microplastics (MPs) and nanoplastics (NPs) facilitate antibiotic resistance genes (ARGs) transfer through horizontal gene transfer (HGT). However, the combined effects of M-NPs and heavy metals on HGT remain poorly understood, and the effects of cell surface properties is neglected. In this study, an antibiotic co-existence heavy metal Cu was used to study its synergetic effect with M-NPs on HGT, with a specific focus on bacterial surface characteristics and physiological responses. Results reveal that NPs amplified Cu(II)'s effect on conjugative transfer of ARGs, while MPs showed mitigation effect. NPs+Cu(II) co-exposure yielded the highest conjugative transfer frequency (4.4-fold) and a 35-fold surge in transformation frequency compared to the control. These disparities stem from bacterial physiological responses, including 4-7-fold elevated reactive oxygen species (ROS), 3-4-fold increased membrane permeability, 1.5-1.8-fold enhanced ATP synthesis, altered drug-resistant efflux and metabolic pathways; Furthermore, cell surface property modulation-Cu(II) stimulated 1.2-fold lipopolysaccharide (LPS) production and M-NPs regulated outer membrane vesicles (OMVs) concentration/sizes, with extracellular polymeric substances (EPS) optimizing interbacterial aggregation for gene transfer. In addition, MPs+Cu(II) induced 49 % viable but non-culturable (VBNC) bacteria and high-dose M-NPs caused excessive bacterial injury/death, reducing gene transfer (VBNC ratio indicating stress severity). These findings highlight co-exposure impacts and offer novel insights into the environmental risks posed by M-NPs and ARGs.

Engineered nanomaterials (ENMs) can alter surface properties of cells and disturb cellular functions and gene expression through direct and indirect contact, exerting unintended impacts on human and ecological health. However, the effects of interactions among environmental factors, such as light, surrounding media, and ENM mixtures, on the mechanisms of ENM toxicity, especially at sublethal concentrations, are much less explored and understood. Therefore, we evaluated cell viability and outer membrane permeability of E. coli as a function of exposure to environmentally relevant concentrations of ENMs, including metal (n-Ag) and metal oxide (n-TiO2, n-Al2O3, n-ZnO, n-CuO, and n-SiO2) nanoparticles under dark and simulated sunlight illumination in MOPS, a synthetic buffer, and Lake Michigan Water (LMW), a freshwater medium. We found that light activates the phototoxicity of n-TiO2 and n-Ag by inducing significant increases in bacterial outer membrane permeability at sublethal doses (< 1 mg/L). Other ENMs, including n-ZnO, n-CuO, n-Al2O3, and n-SiO2, have small to minimal impacts. Toxicities of ENMs were greater in LMW than MOPS due to their different ionic strength and composition. Physical and chemical interactions between n-TiO2 and n-Ag lead to amplified toxic effects of the ENM mixtures that are greater than the additive effects of individual ENMs acting alone. Our results revealed the significant sublethal bacterial stress exerted by ENMs and ENM mixtures at the cell surface in natural environments at low doses, which can potentially lead to further cellular damage and eventually impact overall ecological health.

No abstract available

The aim of the study was to clarify the changes in the pigment composition of Rhodopseudomonas yavorovii IMB B-7620 under the influence of ferric(III) citrate, cobalt(II) chloride, copper(II) chloride and potassium bichromate. Materials and methods. R. yavorovii IMV B-7620 bacteria were grown at + 27 ... + 30 °C for 14 days in ATCC No 1449 medium supplemented with 1.0–12.0 mM ferric(ІІІ) citrate, 1–15 mM cobalt(II) chloride, 0.050–0.500 mM copper(II) chloride, or 0.010–0.045 mM potassium dichromate. The bacterial cells were sedimented, resuspended in acetone, and disintegrated by sonication. The resulting suspension was kept for 24 hours at -20 °C, after which it was centrifuged, and 0.5  ml of supernatant were filtered through membrane filters (pore diameter 0.45 μm). Chromatographic separation of pigments was performed using a high-performance liquid chromatography system. Results. On the 14th day of cultivation under the influence of heavy metal compounds, the qualitative and quantitative changes in the pigment composition in R. yavorovii IMV B-7620 cells occurred. Under the influence of ferric(ІІІ) citrate, cobalt(II) chloride, and potassium dichromate, a decrease in the pigment content in R. yavorovii IMV B-7620 cells was detected. The content of lycopene decreased by 22.1–83.9%, bacteriochlorophyll a – by 33.8–86.0%, compared to the control. Under the influence of copper(II) chloride, not only the pigment content but also the quantity of its isomers increased. Under the influence of the studied metal compounds, a small amount of anhydrorhodovibrin was detected in the cells, whereas it was not detected in the control. Conclusions. Under the influence of heavy metal compounds, changes in the qualitative and quantitative composition of pigments occur in the cells of bacteria R. yavorovii IMV B-7620. Ferric(III) citrate, cobalt(II) chloride and potassium bichromate caused a decrease in the pigment content in R. yavorovii IMV B-7620 cells. Under the influence of copper(II) chloride, not only the content of pigments increased, but also the quantity of their homologues and isomers, in particular lycopene, which can perform a protective function. Under the influence of all the studied metal salts, a small content of anhydrorhodovibrin was detected in the cells, which was not detected in the control. It can also contribute to the protection of cells from stressors.

Abstract In the current scenario nanoparticles (NPs) have gained a breathtaking impetus due to their multidimensional applications in varied fields. In the present effort, biogenic synthesis of Zinc Oxide nanoparticles (ZnO NPs) was carried out using aqueous extract of dried powder of Emblica officinalis (Amla). Physicochemical characterization of nanoparticles was carried out via UV-Visible (UV-Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) wherein the particles were found to be quasi spherical and with a size ranging between 3 and 11 nm. The ZnO nanoparticles exhibited significant antibacterial activity against bacteria as Streptococcus pyogenes MTCC 442, Bacillus cereus MTCC 1272, Escherichia coli MTCC 1687 and Pseudomonas aeruginosa MTCC 4673. The nanoparticles displayed high anti-biofilm activity toward all the bacterial strains, when tested against three different base materials viz. glass, plastic and metal (Aluminum). Further, the nanoparticle treatment of bacterial cells caused changes in their cell membrane permeability, leading to leakage of nucleic acid from the bacterial cells, thereby defining it as the most probable mechanism for their anti-biofilm potential.

Heavy metal (HM) contamination caused by mining and smelting activities can be harmful to soil microbiota, which are highly sensitive to HM stress. Here, we explore the effects of HM contamination on the taxonomic composition, predicted function, and co‐occurrence patterns of soil bacterial communities in two agricultural fields with contrasting levels of soil HMs (i.e., contaminated and uncontaminated natural areas). Our results indicate that HM contamination does not significantly influence soil bacterial α diversity but changes the bacterial community composition by enriching the phyla Gemmatimonadetes, Planctomycetes, and Parcubacteria and reducing the relative abundance of Actinobacteria. Our results further demonstrate that HM contamination can strengthen the complexity and modularity of the bacterial co‐occurrence network but weaken positive interactions between keystone taxa, leading to the gradual disappearance of some taxa that originally played an important role in healthy soil, thereby possibly reducing the resistance of bacterial communities to HM toxicity. The predicted functions of bacterial communities are related to membrane transport, amino acid metabolism, energy metabolism, and carbohydrate metabolism. Among these, functions related to HM detoxification and antioxidation are enriched in uncontaminated soils, while HM contamination enriches functions related to metal resistance. This study demonstrated that microorganisms adapt to the stress of HM pollution by adjusting their composition and enhancing their network complexity and potential ecological functions.