Reactive oxygen species and the bacterial response to lethal stress

Hypermutability of Mycolicibacterium smegmatis due to ribonucleotide reductase-mediated oxidative homeostasis and imbalanced dNTP pools

Ribonucleotide reductase (RNR) catalyzes the synthesis of four deoxyribonucleoside triphosphates (dNTPs), which are essential for DNA replication. Although dNTP imbalances reduce replication fidelity and elevate mutation rates, the impact of RNR dysfunction on Mycobacterium tuberculosis (Mtb) physiology and drug resistance remains unknown. Here, we constructed inducible knockdown strains for the RNR R1 subunit NrdE in Mtb and Mycolicibacterium smegmatis (Msm). NrdE knockdown significantly impaired growth and metabolic imbalances, indirectly disrupting oxidative homeostasis and mycolic acid synthesis, while increasing levels of intracellular ROS accumulation and enhancing cell wall permeability. Additionally, we developed genomic mutant strains, Msm-Y252A and Msm-Q255A, featuring targeted point mutations in the substrate-specific site (S-site) of the RNR loop domain, which determines NDP reduction specificity. The Msm-Y252A displayed a 1.9-fold decrease in dATP and increases in dGTP (1.6-fold), dTTP (9.0-fold), and dCTP (1.3-fold). In contrast, Msm-Q255A exhibited elevated intracellular levels of dGTP (1.6-fold), dTTP (6.1-fold), and dATP (1.5-fold), while dCTP levels remained unchanged. Neither the NrdE knockdown strain nor the S-site mutants exhibited direct resistance development; however, they both showed genomic instability, enhancing the emergence of rifampicin-resistant mutants, even with a 70-fold and a 25-fold increase in mutation frequency for Msm-Y252A and Msm-Q255A, respectively. This study demonstrates that NrdE is integral to Mycobacterium survival and genomic stability and that its RNR dysfunction creates a mutagenic environment under selective pressure, indirectly contributes to the development of drug resistance, positioning NrdE as an effective target for therapeutic strategies and a valuable molecular marker for early detection of drug-resistant Mtb.

Virome drift in ulcerative colitis patients: faecal microbiota transplantation results in minimal phage engraftment dominated by microviruses

Ulcerative colitis (UC) is an inflammatory bowel disease characterized by recurrent colonic inflammation. Standard treatments focus on controlling inflammation but remain ineffective for one-third of patients. This underscores the need for alternative approaches, such as fecal microbiota transplantation (FMT), which transfers healthy donor microbiota to patients. The role of viruses in this process, however, remains underexplored. To address this, we analyzed the gut virome using metagenomic sequencing of enriched viral particles from 320 longitudinal fecal samples of 44 patients enrolled in the RESTORE-UC FMT trial. Patients were treated with FMTs from healthy donors (allogenic, treatment) or themselves (autologous, control). We found that colonic inflammation, both its presence and location, had a greater impact on the gut virome than FMT itself. In autologous FMT patients, the virome was unstable and showed rapid divergence over time, a phenomenon we termed virome drift. In allogenic FMT patients, the virome temporarily shifted toward the healthy donor, lasting up to 5 weeks and primarily driven by microviruses. Notably, two distinct virome configurations were identified and linked to either healthy donors or patients. In conclusion, inflammation strongly affects the gut virome in UC patients, which may lead to instability and obstruct the engraftment of allogeneic FMT.

Nitazoxanide inhibits pili assembly by targeting BamB to synergize with polymyxin B against drug-resistant Escherichia coli

Gram-negative bacteria rely on pili assembly for pathogenicity, with the chaperone-usher (CU) pathway regulating pilus biogenesis. Nitazoxanide (NTZ) inhibits CU pathway-mediated P pilus biogenesis by specifically interfering with the proper folding of the outer membrane protein (OMP) usher, primarily mediated by the β-barrel assembly machinery (BAM) complex. In this study, we identified the BAM complex components BamB and the BamA POTRA2 domain as key binding targets for NTZ. Molecular dynamics simulations and Bio-Layer Interferometry revealed that BamB residues S61 and R195 are critical for NTZ binding. NTZ activated the Cpx two-component system and induced inner membrane perturbations, which resulted from the accumulation of misfolded P pilus subunits. Upregulation of the ibpAB gene, which protects the bacteria against NTZ-induced oxidative stress, was also observed. Importantly, NTZ combined with polymyxin B enhanced the latter's antibacterial activity against both susceptible and MCR-positive E. coli strains. This enhancement was achieved through NTZ-induced increases in inner membrane permeability, oxidative stress, and inhibition of efflux pump activity and biofilm formation. This study provides new insights into the antimicrobial mechanism of NTZ and highlights its potential as an antibiotic adjuvant by targeting BamB to inhibit the CU pathway, restoring the efficacy of polymyxin B against multidrug-resistant bacteria.

The ability of hydrogen peroxide (H2O2) to degrade saxitoxin-, microcystin-, anatoxin-, and non-toxin-producing strains of the harmful cyanobacterium, Dolichospermum

Hydrogen peroxide (H2O2) has been used to mitigate cyanobacterial harmful algal blooms (CHABs), yet little is known about how H2O2 affects specific CHAB-forming genera as well as cyanotoxins beyond microcystin. This project examined the dose-dependent effects of H2O2 on six strains of Dolichospermum spp. including those that produce saxitoxin, anatoxin-a, and microcystin. Beyond toxins, this study quantified changes in photosynthetic efficiency, cell density, H2O2 concentration, and N2-fixation rates. All strains were sensitive to H2O2 with responses being dependent on dose (0-30 mg L-1) of H2O2, cell density, and strain. At 1 × 105 cells mL-1, 4 mg H2O2 L-1 significantly reduced cell density, photosynthetic efficiency, toxins, and N2-fixation rates of all strains (p < 0.05 for all compared to controls). At 1 × 106 cells mL-1, however, higher doses of H2O2 were needed to reduce one or more of the variables, with some strains unaffected by as much as 15 mg L-1, a concentration known to harm zooplankton and invertebrates. While H2O2 degraded anatoxin-a at all cell densities and doses, at 1 × 106 cells mL-1 neither microcystin nor saxitoxin were significantly degraded after four days, even by 15 mg H2O2 L-1, despite significant reduction in Dolichospermum cell densities. This finding suggests that during dense Dolichospermum blooms, H2O2 treatment may destroy cells but may concurrently liberate saxitoxin or microcystin that persists in the water column and enters food webs. Collectively, this study demonstrated that although H2O2 can efficiently lyse Dolichospermum cells, doses needed to mitigate dense blooms of all strain types (≥15 mg L-1) may harm non-target organisms and may not effectively degrade saxitoxin and microcystin.

Lipidated SNAPP-Stars Target and Kill Multidrug-Resistant Bacteria within Minutes

The fast emergence of bacteria resistance has already threatened global health, and immediate action is required before the emergence of another global pandemic. Despite substantial progress in the chemical synthesis of novel antimicrobial compounds and advancements in understanding antimicrobial resistance, there has been only a handful of new antibiotics coming to the market. Structurally Nanoengineered Antimicrobial Peptide Polymers (SNAPP-stars) are a new class of antimicrobials. Here, we show that lipidation of lysine-valine 16-armed SNAPP-star, S16 (lipo-SNAPP-star) where the N-terminal arms are conjugated with different fatty acids (caproic, C6, lauric, C12, and stearic acid, C18) enhanced the antimicrobial activity toward S. aureus and MRSA. Lipidation enhanced activity by targeting the SNAPP-stars to the bacterial surface by binding to peptidoglycan, leading to greater inner membrane disruption and depolarization. Lipo-SNAPP-stars killed bacteria in under a minute, whereas vancomycin took >16 h. Lipo-SNAPP-stars were found to preferentially target and kill MRSA rather than S. aureus in a mixed bacteria model. Lipid chain length affected activity, with C6-S16 having greater activity compared to C12-S16 > C18-S16. Lauric and stearic acid enhanced SNAPP-star binding to the bacterial surface and membrane depolarization but impeded SNAPP-stars' ability to transit through the peptidoglycan layer to disrupt the inner membrane. Microbial flow cytometry showed that lipidation aided binding to bacteria via lipoteichoic acid and specifically to peptidoglycan. Further, lipid length enhanced bacterial binding with C18-S16 > C12-S16 > C6-S16 = S16, which contrasts the activity order of C6-S16 > S16 ≫ C12-S16 ≫ C18-S16. Our data demonstrate that lipidation enhances antimicrobial activity by targeting and binding an antimicrobial to peptidoglycan, but increasing lipid length reduces activity by retaining the antimicrobial in the outer layer. Lipidation of SNAPP-stars did not increase cytotoxicity, with C6-S16 having an improved therapeutic index compared to S16. Our data show how lipidation of SNAPP-stars enhances its antimicrobial activity, resulting in a highly biocompatible antimicrobial that targets and kills the "superbug" MRSA within minutes.

Magnesium Infusion on Dental Implants and Its Impact on Osseointegration and Biofilm Development: A Review

Dental implants have gained global popularity as a treatment option for tooth loss. The success of dental implants depends on their optimal integration into the tissues of the alveolar bone and the periodontium. However, several factors can hinder the proper osseointegration of implants, with the growth of biofilm on the implant surface and subsequent peri-implant infections being significant concerns. To overcome this challenge, researchers have explored the incorporation of antimicrobial agents onto metallic implant surfaces to mitigate biofilm growth. Ideally these agents should promote osteogenesis while exhibiting antibacterial effects. Magnesium (Mg) has emerged as a promising dual-function implant coating due to its osteogenic and antibacterial properties. Despite several studies, the precise mechanisms behind osteoinductive and antimicrobial effect of Mg is unclear, as yet. This review aims to collate and discuss the utility of Mg as a dental implant coating, its impact on the osteogenic process, potential in mitigating microbial growth, and prospects for the future. A comprehensive literature search was conducted across several databases and the findings reveal the promise of Mg as a dual-function dental implant coating material, both as a standalone agent and in combination with other materials. The antibacterial effect of Mg is likely to be due to its (1) toxicity particularly at high concentrations, (2) the production or reactive oxygen species, and (3) pH modulation, while the osteoinductive effect is due to a complex series of cellular and biochemical pathways. Despite its potential both as a standalone and composite coating, challenges such as degradation rate, leaching, and long-term stability must be addressed. Further research is needed to understand the utility of Mg as an implant coating material, particularly in relation to its antibacterial activity, osseointegration, and longevity in the oral milieu.

Revitalizing Antibiotics with Macromolecular Engineering: Tackling Gram-Negative Superbugs and Mixed Species Bacterial Biofilm Infections In Vivo

The escalating prevalence of multidrug-resistant Gram-negative pathogens, coupled with dwindling antibiotic development, has created a critical void in the clinical pipeline. This alarming issue is exacerbated by the formation of biofilms by these superbugs and their frequent coexistence in mixed-species biofilms, conferring extreme antibiotic tolerance. Herein, we present an amphiphilic cationic macromolecule, ACM-AHex, as an innovative antibiotic adjuvant to rejuvenate and repurpose resistant antibiotics, for instance, rifampicin, fusidic acid, erythromycin, and chloramphenicol. ACM-AHex mildly perturbs the bacterial membrane, enhancing antibiotic permeability, hampers efflux machinery, and produces reactive oxygen species, resulting in a remarkable 64-1024-fold potentiation in antibacterial activity. The macromolecule reduces bacterial virulence and macromolecule-drug cocktail significantly eradicate both mono- and multispecies bacterial biofilms, achieving >99.9% bacterial reduction in the murine biofilm infection model. Demonstrating potent biocompatibility across multiple administration routes, ACM-AHex offers a promising strategy to restore obsolete antibiotics and combat recalcitrant Gram-negative biofilm-associated infections, advocating for further clinical evaluation as a next-generation macromolecular antibiotic adjuvant.

Deciphering meropenem persistence in Acinetobacter baumannii facilitates discovery of anti-persister activity of thymol

Decades of antibiotic misuse have accelerated the emergence of multi- and extensively drug-resistant bacteria. Bacterial pathogens employ several strategies such as antibiotic resistance, tolerance, and biofilm formation in response to extreme environments and antibiotic stress. Another crucial survival mechanism involves the stochastic generation of bacterial subpopulations known as persisters, which can endure high concentrations of antibiotics. Upon removal of antibiotic stress, these subpopulations revert back to their original phenotype which links them to the relapse and recalcitrance of chronic infections, a significant problem in clinical settings. Persistent infections are particularly notable in Acinetobacter baumannii, a top-priority ESKAPE pathogen, where carbapenems serve as last-resort antibiotics. Several reports indicate the rising therapeutic failure of carbapenems due to persistence, underscoring the importance of developing anti-persister therapeutics. In this study, we explored the mechanisms of transient persister formation in A. baumannii against meropenem. Our investigation revealed significant changes in membrane properties and energetics in meropenem persisters of A. baumannii, including a noteworthy increase in tolerance to other antibiotics. This understanding guided the evaluation of an in-house collection of GRAS status compounds for their potential anti-persister activity. The compound thymol demonstrated remarkable inhibitory activity against meropenem persisters of A. baumannii and other ESKAPE pathogens. Further investigation revealed its impact on persister cell physiology, including efflux pump inhibition and disruption of cellular respiration. Given our results, we propose a compelling strategy where thymol could be employed either as a monotherapy or in combination with meropenem in anti-persister therapeutics.

Impacts of sulfamethoxazole on heterotrophic nitrification-aerobic denitrification bacteria and its response strategies: Insights from physiology to proteomics

The effects of sulfonamide antibiotics on heterotrophic nitrification-aerobic denitrification (HN-AD) and the response mechanisms of HN-AD bacteria are not fully understood. This study investigated the physiological changes and proteomic responses of the HN-AD bacteria Pseudomonas stutzeri (P. stutzeri) under varying concentrations of sulfamethoxazole (SMX). Results indicated that SMX inhibited the growth and HN-AD performance of P. stutzeri in a concentration-dependent manner. SMX exposure led to decreased motility, reduced electron transfer system activity, and diminished activities of key denitrifying enzymes, accompanied by increased levels of intracellular reactive oxygen species and compromised cell membrane integrity. Additionally, the production of extracellular polymeric substances and self-aggregation ability of P. stutzeri initially increased and then decreased with rising SMX concentrations. Proteomic analysis revealed that SMX primarily suppressed pathways involved in bacterial chemotaxis, ABC transporters, two-component systems, fatty acid metabolism, and nitrogen metabolism. In response, P. stutzeri upregulated pathways associated with starch and sucrose metabolism, carotenoid biosynthesis, styrene degradation, O-antigen nucleotide sugar biosynthesis, and the pentose phosphate pathway. These findings provide insights into the effects of sulfonamide antibiotics on HN-AD bacteria and their response mechanisms, offering references for the application of HN-AD processes in treating antibiotic-containing wastewater.

Exploring the microbial communities in coastal cenote and their hidden biotechnological potential

Bacterial secondary metabolites are crucial bioactive compounds with significant therapeutic potential, playing key roles in ecological processes and the discovery of novel antimicrobial agents and natural products. Cenotes, as extreme environments, harbour untapped microbial diversity and hold an interesting potential as sources of novel secondary metabolites. While research has focused on the fauna and flora of cenotes, the study of their microbial communities and their biosynthetic capabilities remains limited. Advances in metagenomics and genome sequencing have greatly improved the capacity to explore these communities and their metabolites. In this study, we analysed the microbial diversity and biotechnological potential of micro-organisms inhabiting sediments from a coastal cenote. Metagenomic analyses revealed a rich diversity of bacterial and archaeal communities, containing several novel biosynthetic gene clusters (BGCs) linked to secondary metabolite production. Notably, polyketide synthase BGCs, including those encoding ladderanes and aryl-polyenes, were identified. Bioinformatics analyses of these pathways suggest the presence of compounds with potential industrial and pharmaceutical applications. These findings highlight the biotechnological value of cenotes as reservoirs of secondary metabolites. The study and conservation of these ecosystems are essential to facilitate the discovery of new bioactive compounds that could benefit various industries.

Emilia sonchifolia (L.) DC. inhibits the growth of Methicillin-Resistant Staphylococcus epidermidis by modulating its physiology through multiple mechanisms

Bloodstream infections (BSIs) are a public health concern, causing substantial morbidity and mortality. Staphylococcus epidermidis (S. epidermidis) is a leading cause BSIs. Antibiotics targeting S. epidermidis have been the mainstay of treatment for BSIs, however their efficacy is diminishing in combating with drug-resistant bacteria. Therefore, alternative treatments for antibiotic-resistant infections are urgently required. Studies have demonstrated that certain traditional Chinese medicine (TCM) exhibit notable antimicrobial activity and can help mitigate bacterial resistance. Among these, The ethanol extract of Emilia sonchifolia (L.) DC (E. sonchifolia) (10 g crude drug/1 g extract ) exhibits a noteworthy anti-methicillin-resistant S. epidermidis (MRSE) effect. This study explores antibacterial activity and underlying mechanisms of E. sonchifolia against MRSE. The antibacterial activity of E. sonchifolia against MRSE was assessed in vitro by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The MRSE-induced mouse BSIs model was used to evaluate the antibacterial activity of E. sonchifolia in vivo. Proteomic and transcriptomic analyses were performed to elucidate the underlying antibacterial mechanisms. The MIC and MBC values of E. sonchifolia against MRSE were 5 mg/mL and 20 mg/mL, respectively. In vivo, E. sonchifolia effectively treated MRSE-induced BSIs. Additionally, proteomic and transcriptomic analyses revealed considerable down-regulation of purine metabolism, that were associated with oxidative stress and cell wall synthesis. The enzyme linked immunosorbent assay(ELISA) results showed decreased levels of inosine monophosphate (IMP), Adenosine monophosphate(AMP) and guanine monophosphate (GMP), indicating inhibited purine metabolism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis confirmed bacterial cell wall damage. E. sonchifolia exerts antibacterial effects by inhibiting purine metabolism, promoting bacterial oxidative stress, and impairing cell wall synthesis. These findings provide novel insights into the mechanistic understanding of E. sonchifolia's efficacy against MRSE, offering potential strategies for managing MRSE infections.

N-Acetyl Cysteine and Vitamin C Modulate the Antibiotic Efficacy Against Escherichia coli Cells

Supplements with their own beneficial effect on hosts are consumed by us. N-acetyl cysteine (NAC) and Vitamin C (Vit C) are antioxidants and supplements, consumed for their beneficial properties. The present investigation evaluates the effect of their antioxidant property on antibiotic efficacy against Escherichia coli cells from different physiological states, including exponential and stationary-phase, cell aggregates, and in-vitro stress-induced persister cells. Survival was measured in cfu/mL by cfu (colony-forming unit) counting, with efficacy determined by log-fold change in survival by comparing CFUs in antibiotics alone and antibiotic + antioxidant combinations. Fluoroquinolones in the presence of NAC reduced ∼1 log CFUs of log-phase and persister cells, while Vit C reduced CFUs (∼1-3-log increase) of cells from all physiological states. Aminoglycosides results were inconclusive; streptomycin's activity declined (∼1-3-log increase in survival), whereas amikacin's activity potentiated (∼1-log reduction in cfu/mL). Rifampicin's showed reduced activity (∼2-3 log increase in survival) with Vit C in all the states and a ∼1-2 log increase with NAC, especially in cell aggregates and persisters. Beta-lactams activity showed variability, with amoxicillin and ampicillin not being influenced, but ceftriaxone showed significant reduction of efficacy (∼2-3-log increase in survival) in all the treatments. The findings suggest that the overall impact of antioxidants on antibiotic efficacy varies depending on the antibiotic class.

Proteomic Insights into Psychrophile Growth in Perchlorate-Amended Subzero Conditions: Implications for Martian Life Detection

Since the discovery of perchlorates in martian soils, astrobiologists have been curious if and how life could survive in these low-water, high-salt environments. Perchlorates induce chaotropic and oxidative stress but can also confer increased cold tolerance in some extremophiles. Though bacterial survival has been demonstrated at subzero temperatures and in perchlorate solution, proteomic analysis of cells growing in an environment like martian regolith brines-perchlorate with subzero temperatures-has yet to be demonstrated. By defining biosignatures of survival and growth in perchlorate-amended media at subzero conditions, we move closer to understanding the mechanisms that underlie the feasibility of life on Mars. Colwellia psychrerythraea str. 34H (Cp34H), a marine psychrophile, was exposed to perchlorate ions in the form of a diluted Phoenix Mars Lander Wet Chemistry Laboratory solution at -1°C and -5°C. At both temperatures in perchlorate-amended media, Cp34H grew at reduced rates. Mass spectrometry-based proteomics analyses revealed that proteins responsible for mitigating effects of oxidative and chaotropic stress increased, while cellular transport proteins decreased. Cumulative protein signatures suggested modifications to cell-cell or cell-surface adhesion properties. These physical and biochemical traits could serve as putative identifiable biosignatures for life detection in martian environments.

Biosynthesis of Gold Nanostructures and Their Virucidal Activity Against Influenza A Virus

Bacteria in natural environments often encounter high concentrations of metal ions, leading to the development of defense mechanisms such as chemical reduction. This process can result in the formation of nanostructures (NS) ranging from 1-100 nm, which have valuable properties for various applications, including as virucidal agents. Currently, metallic NS with virucidal activity are used in disinfectants and surface protection products. However, their production mainly relies on physical and chemical methods, which are often complex, toxic, and energy-intensive. A sustainable alternative is the biosynthesis of nanostructures. Our research focuses on the biosynthesis of gold nanostructures (AuNS) using environmental bacteria and their proteins, with the aim of exploring their potential as agents to destroy the influenza A virus. We screened bacteria under conditions with HAuCl4, identifying eight microorganisms capable of growing in high gold concentrations. Staphylococcus haemolyticus BNF01 showed the highest resistance and Au(III) reduction, growing up to 0.25 mM in HAuCl4. Bioinformatic analysis revealed five proteins with potential Au(III)-reductase activity, which were cloned and expressed in Escherichia coli. These proteins reduced gold to form AuNPs, which were purified, characterized for size, shape, and surface charge, and tested against influenza A, showing significant virucidal effects, likely due to interactions with viral proteins.

Exogenous cystine increases susceptibility of drug-resistant Salmonella to gentamicin by promoting oxidation of glutathione metabolism and imbalance of intracellular redox levels

Introduction

Antibiotic overuse has caused the development of bacterial resistance, which is a major threat to public health. Intracellular metabolic processes are essential for maintaining the normal physiological activities of bacteria, and an increasing body of research has demonstrated a significant association between metabolic alterations and the development of drug resistance. Numerous studies have demonstrated that the addition of adjuvants can counteract bacterial antibiotic resistance.

Method

Cystine treatment was verified in vitro to promote the lethal effect of gentamicin on Salmonella using in vitro bactericidal counting methods. The metabolic differences in Salmonella enterica Typhimurium standard strain ATCC 14028 with or without the addition of cystine were analyzed via untargeted metabolomics. The multifunctional electronic enzyme marker was used to determine intracellular reduced glutathione/oxidized glutathione (GSH/GSSG), ferrous iron on (Fe2+), and reactive oxygen species (ROS) levels. The expression of glutathione and stress genes was determined using real-time quantitative PCR.

Result

We confirmed that exogenous cystine increased the lethal effect of gentamicin against strain S. enterica Typhimurium (ATCC 14028) and other clinically resistant Salmonella serotypes. Exogenous cystine stimulated the metabolism of the cell and activated the glutathione pathway while altering the GSH/GSSG ratio, which placed bacteria in a state of redox imbalance with increased Fe2+ and ROS levels. Our results suggest that when bacterial redox levels are reprogrammed, bacterial susceptibility to antibiotics can also change.

Discussion

This study confirms that cystine enhances the antimicrobial efficacy of gentamicin against drug-resistant Salmonella. Through the application of metabolomics, the underlying metabolic mechanisms by which cystine exerts its effects on Salmonella have been elucidated, offering a novel perspective in the domain of metabolic reprogramming aimed at counteracting drug resistance. Furthermore, these findings reinforce the potential role of small-molecule metabolites as effective adjuvants to enhance antibiotic action.

Graveyard effects of antimicrobial nanostructured titanium over prolonged exposure to drug resistant bacteria and fungi

Innovations in nanostructured surfaces have found a practical place in the medical area with use in implant materials for post-operative infection prevention. These textured surfaces should be dual purpose: (1) bactericidal on contact and (2) resistant to biofilm formation over prolonged periods. Here, hydrothermally etched titanium surfaces were tested against two highly antimicrobial resistant microbial species, methicillin-resistant Staphylococcus aureus and Candida albicans. Two surface types - unmodified titanium and nanostructured titanium - were incubated in a suspension of each microbial strain for 1 day and 7 days. Surface topography and cross-sectional information of the microbial cells adhered to the surfaces, along with biomass volume and live/dead rate, showed that while nanostructured titanium was able to kill microbes after 1 day of exposure, after 7 days, the rate of death becomes negligible when compared to the unmodified titanium. This suggests that as biofilms mature on a nanostructured surface, the cells that have lysed conceal the nanostructures and prime the surface for planktonic cells to adhere, decreasing the possibility of structure-induced lysis. Synchrotron macro-attenuated total reflection Fourier transform infrared (macro ATR-FTIR) micro-spectroscopy was used to elucidate the biochemical changes occurring following exposure to differing surface texture and incubation duration, providing further understanding into the effects of surface morphology on the biochemical molecules (lipids, proteins and polysaccharides) in an evolving and growing microbial colony.

A shape-adaptive hydrogel with dual antibacterial and osteogenic properties for alveolar bone defect repair

Alveolar bone defects are often irregular in shape and can severely affect patients' physical and psychological well-being, posing significant challenges in treatment, particularly in cases complicated by systemic diseases. This study presents a shape-adaptive hydrogel with sequential antibacterial and osteogenic functions designed to repair irregular bone defects associated with osteoporosis. Naringin, an estrogen analogue, was conjugated to the hydrogel via disulfide bonds and then uniformly mixed with nano-hydroxyapatite (nano-HAP) to create microspheres. These microspheres were uniformly dispersed within the naringin-loaded hydrogel, forming an injectable and photocurable suspension. Upon implantation, naringin is rapidly released due to diffusion along the concentration gradient and initial hydrogel degradation, providing antibacterial effects and preventing infection. As bone repair progresses, the hydrogel undergoes further degradation and the disulfide bonds break, so that naringin is continuously released, which enhances osteoblast differentiation and inhibits osteoclast differentiation. Material characterization confirmed the presence of disulfide bonds and the sustained release profile of naringin. Both in vitro and in vivo experiments demonstrated the hydrogel's excellent biocompatibility and its effectiveness in repairing regular mandibular defects as well as irregular alveolar bone defects associated with osteoporosis. This hydrogel provides a promising strategy for the development of advanced biomaterials tailored to the complex requirements of irregular bone defect repair under osteoporotic conditions.

Colostrum-Derived Melatonin Plus PEG Microspheres Modulate the Oxidative Metabolism of Human Colostrum Phagocytes

BACKGROUND/OBJECTIVES

Exogenous melatonin adsorbed onto PEG microspheres can modulate the functional activity of phagocytes in colostrum, but no data are available on the activity of melatonin found in colostrum. Therefore, the objective of this study was to extract melatonin from human colostrum, develop and characterize PEG microspheres with the extracted melatonin adsorbed onto them, and evaluate the effects of this system on the oxidative metabolism of colostrum phagocytes.

METHODS

Thirty colostrum samples were collected; ten were used for melatonin extraction, while twenty were used to obtain phagocytes. Melatonin was extracted from the colostrum supernatant through affinity chromatography and quantified by ELISA. The polyethylene glycol microspheres produced were analyzed using fluorescence microscopy and flow cytometry. Oxidative metabolism was assessed by measuring the release of the superoxide anion and superoxide enzymes. A control was conducted using commercial melatonin.

RESULTS

The fluorescence microscopy and flow cytometry analyses demonstrated that PEG microspheres can adsorb melatonin. There was an increase in superoxide release in phagocytes incubated with colostrum-derived or synthetic melatonin. When exposed to bacteria, colostrum phagocytes treated with colostrum melatonin adsorbed to PEG microspheres exhibited increased superoxide, accompanied by a decrease in the release of superoxide dismutase (SOD) and a lower SOD-to-superoxide ratio. In contrast, synthetic melatonin reduced the release of superoxide and increased the release of the enzyme and the SOD-to-superoxide ratio.

CONCLUSIONS

These data highlight the importance of melatonin on cellular metabolism and suggest that colostrum-derived melatonin may be a more effective option for controlling oxidative metabolism, particularly during infectious processes.

Deciphering the acidophilia and acid resistance in Acetilactobacillus jinshanensis dominating baijiu fermentation through multi-omics analysis

Lactic acid bacteria (LAB) are pivotal in constructing the intricate bio-catalytic networks underlying traditional fermented foods such as Baijiu. However, LAB and their metabolic mechanisms are partially understood in Moutai flavor Baijiu fermentation. Here, we found that Acetilactobacillus jinshanensis became the· dominant species with relative abundance reaching 92%, where the acid accumulated rapidly and peaked at almost 30 g/kg in Moutai flavor Baijiu. After separation, purification, and cultivation, A. jinshanensis exhibited pronounced acidophilia and higher acid resistance compared to other LAB. Further integrated multi-omics analysis revealed that fatty acid synthesis, cell membrane integrity, pHi and redox homeostasis maintenance, protein and amide syntheses were possibly crucial acid-resistant mechanisms in A. jinshanensis. Structural proteomics indicated that the surfaces of A. jinshanensis proteases contained more positively charged amino acid residues to maintain protein stability in acidic environments. The genes HSP20 and acpP were identified as acid-resistant genes for A. jinshanensis by heterologous expression analysis. These findings not only enhance our understanding of LAB in Baijiu, providing a scientific basis for acid regulation for production process, but also offer valuable insights for studying core species in other fermentation systems.

Adaptations of Escherichia coli K 12 to Synchrotron Sourced THz Radiation

The biological effects of electromagnetic field (EMF) irradiation in the terahertz (THz) range remain ambiguous, despite numerous studies that have been conducted. In this paper, the metabolic response of Escherichia coli K 12 to EMF irradiation was examined using a 1.0 W m-2 incident synchrotron source (SS) in the range of 0.5-18.0 THz for over 90 min of continuous exposure at 25 °C. This continuous SS THz exposure induced periodic decreases in the cell growth after 10, 20, and 40 min of exposure compared to a time-matched control; however, the number of viable cells thereafter grew. The physiological status of treated cells immediately after exposure was assessed by using the direct plate counting technique and electron microscopy. Analysis of scanning electron microscopy (SEM) and high-resolution cryogenic transmission electron (cryo-TEM) micrographs showed that approximately 20% of the SS THz-exposed E. coli cells exhibited a deformed outer membrane, membrane perturbations, and leakage of cytosol. The proteome changes in E. coli cells after 18 h postexposure were associated with cellular response to plasma membrane regulation including phospholipid biosynthetic process and osmotic stress. The results of this study highlighted that E. coli cells can promptly activate the fundamental mechanisms in response to prolonged exposure to THz radiation that are evolutionarily developed to withstand other environmental stressors.

A supervised machine learning tool to predict the bactericidal efficiency of nanostructured surface

The emergence and rapid spread of multidrug-resistant bacterial strains is a growing concern of public health. Inspired by the natural bactericidal surfaces of lotus leaves and shark skin, increasing attention has been focused on the use of mechano-bactericidal methods to create surfaces with antibacterial and/or bactericidal effects. There have been several studies exploring the bactericidal effect of nanostructured surfaces under various combinations of parameters. However, the correlation and synergies between these factors still need to be clarified. Recently machine learning (ML), which enables prediction or decision-making based on data, has been used in the field of biomaterials with promising results. In this study, we explored ML in nanotechnology to investigate the antimicrobial potential of nanostructured surfaces. A dataset of nanostructured surfaces and their antimicrobial properties was built by extracting the published literature. Based on the literature review and the distribution of our dataset, 70% bactericidal efficiency was selected as a practical benchmark for our classification model that balances stringent bactericidal performance with achievable targets in diverse conditions. Subsequently, we developed an ML classification model, which demonstrated an 81% accuracy in its predictive capability. A regression model was further developed to predict the value of bactericidal efficiency for nanostructured surfaces. Feature importance analysis of the ML models suggested that nanotopographical features have a greater influence on bactericidal properties than material properties, thus providing insight into the principles of the mechano-bactericidal effect of nanostructured surfaces. Overall, this ML model tool could help researchers to effectively select and design the parameters of the surface structure prior to experimentation, thereby improving the timeliness and reducing the number of experiments and the associated costs.

The ability in managing reactive oxygen species affects Escherichia coli persistence to ampicillin after nutrient shifts

Bacterial persistence profoundly impacts biofilms, infections, and antibiotic effectiveness. Persister formation can be substantially promoted by nutrient shift, which commonly exists in natural environments. However, mechanisms that promote persister formation remain poorly understood. Here, we investigated the persistence frequency of Escherichia coli after switching from various carbon sources to fatty acid and observed drastically different survival rates. While more than 99.9% of cells died during a 24-hour ampicillin (AMP) treatment after the glycerol to oleic acid (GLY → OA + AMP) shift, a surprising 56% of cells survived the same antibiotic treatment after the glucose to oleic acid (GLU → OOA + AMP) shift. Using a combination of single-cell imaging and time-lapse microscopy, we discovered that the induction of high levels of reactive oxygen species (ROS) by AMP is the primary mechanism of cell killing after switching from gluconeogenic carbons to OA + AMP. Moreover, the timing of the ROS burst is highly correlated (R2 = 0.91) with the start of the rapid killing phase in the time-kill curves for all gluconeogenic carbons. However, ROS did not accumulate to lethal levels after the GLU → OA + AMP shift. We also found that the overexpression of the oxidative stress regulator and ROS detoxification enzymes strongly affects the amounts of ROS and the persistence frequency following the nutritional shift. These findings elucidate the different persister frequencies resulting from various nutrient shifts and underscore the pivotal role of ROS. Our study provides insights into bacterial persistence mechanisms, holding promise for targeted therapeutic interventions combating bacterial resistance effectively.

IMPORTANCE

This research delves into the intriguing realm of bacterial persistence and its profound implications for biofilms, infections, and antibiotic efficacy. The study focuses on Escherichia coli and how the switch from different carbon sources to fatty acids influences the formation of persister-resilient bacterial cells resistant to antibiotics. The findings reveal a striking variation in survival rates, with a significant number of cells surviving ampicillin treatment after transitioning from glucose to oleic acid. The key revelation is the role of reactive oxygen species (ROS) in cell killing, particularly after switching from gluconeogenic carbons. The timing of ROS bursts aligns with the rapid killing phase, highlighting the critical impact of oxidative stress regulation on persistence frequency. This research provides valuable insights into bacterial persistence mechanisms, offering potential avenues for targeted therapeutic interventions to combat bacterial resistance effectively.

Electroless Ag nanoparticle deposition on TiO2 nanorod arrays, enhancing photocatalytic and antibacterial properties

HYPOTHESIS

The small size of the nanoparticles used to obtain high surface area photocatalysts makes their removal from solution difficult. Producing photocatalysts on substrates would alleviate this limitation. Adding heterojunctions to photocatalysts, for example, TiO2/Ag, could improve photocatalytic performance due to Schottky junction formation and introduce antibacterial properties.

EXPERIMENTS

TiO2 nanorod arrays were synthesised on a substrate via a hydrothermal approach, on which Ag nanoparticles were deposited using an electroless plating technique with varied deposition times and metal precursor concentrations. Photocatalytic performance was evaluated by monitoring Rhodamine B (RhB) degradation under ultraviolet light and antibacterial properties of the films tested using Methicillin-resistant Staphylococcus aureus.

FINDINGS

The Ag nanoparticle content was controlled by the Ag deposition process. The TiO2/Ag nanorod array containing 6.6 atomic% Ag as nanoparticles of ∼ 25 nm in diameter degraded 88 % of the RhB in 6 h compared to 54 % degradation for bare TiO2 nanorods under the same reaction conditions. Decreased photoluminescence with heterojunction formation would indicate electron transfer from the TiO2 into the Ag nanoparticles, thereby reducing charge carrier recombination. The antibacterial test conducted in the dark revealed enhanced performance for the TiO2/Ag sample compared to TiO2 nanorods against Methicillin-resistant Staphylococcus aureus after 16 h exposure with a death rate of 84 %.

Organic extracts from sustainable hybrid poplar hairy root cultures as potential natural antimicrobial and antibiofilm agents

In order to meet growing consumer demands in terms of naturalness, the pharmaceutical, food, and cosmetic industries are looking for active molecules of plant origin. In this context, hairy roots are considered a promising biotechnological system for the sustainable production of compounds of interest. Poplars (genus Populus, family Salicaceae) are trees of ecological interest in temperate alluvial forests and are also cultivated for their industrial timber. Poplar trees also produce specialized metabolites with a wide range of bioactive properties. The present study aimed to assess the hybrid poplar hairy root extracts for antimicrobial and antibiofilm activities against four main life-threatening strains of Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. Ethyl acetate extracts from two hairy root lines (HP15-3 and HP A4-12) showed significant antibacterial properties as confirmed by disc diffusion assay. Antibiofilm activities were found to be dose dependent with significant biofilm inhibition (75-95%) recorded at 1000 µg.mL-1 in all the bacterial strains tested. Dose-dependent enhancement in the release of exopolysaccharides was observed in response to treatment with extracts, possibly because of stress and bacterial cell death. Fluorescence microscopy confirmed loss of cell viability of treated bacterial cells concomitant with increased production of reactive oxygen species compared to the untreated control. Overall, this study demonstrates for the first time a high potential of poplar hairy root extracts as a natural and safe platform to produce antimicrobial agents in pharmaceutical, food, industrial water management, or cosmetic industries.

The generation and transformation mechanisms of reactive oxygen species in the environment and their implications for pollution control processes: A review

Reactive oxygen species (ROS), substances with strong activity generated by oxygen during electron transfer, play a significant role in the decomposition of organic matter in various environmental settings, including soil, water and atmosphere. Although ROS has a short lifespan (ranging from a few nanoseconds to a few days), it continuously generated during the interaction between microorganisms and their environment, especially in environments characterized by strong ultraviolet radiation, fluctuating oxygen concentration or redox conditions, and the abundance of metal minerals. A comprehensive understanding of the fate of ROS in nature can provide new ideas for pollutant degradation and is of great significance for the development of green degradation technologies for organic pollutants. At present, the review of ROS generally revolves around various advanced oxidation processes, but lacks a description and summary of the fate of ROS in nature, this article starts with the definition of reactive oxidants species and reviews the production, migration, and transformation mechanisms of ROS in soil, water and atmospheric environments, focusing on recent developments. In addition, the stimulating effects of ROS on organisms were reviewed. Conclusively, the article summarizes the classic processes, possible improvements, and future directions for ROS-mediated degradation of pollutants. This review offers suggestions for future research directions in this field and provides the possible ROS technology application in pollutants treatment.

Compounds Derived from 5-Fluoropyridine and Benzo[b]thiophene: Killing Mycobacterium tuberculosis and Reducing its Virulence

The rise of drug-resistant Mycobacterium tuberculosis (Mtb) has extended the duration of tuberculosis (TB) treatment and reduced the likelihood of cure. One strategy to combat this issue is the development of inhibitors targeting the virulence factors of bacterial pathogens. Mtb' catalase (KatG) is crucial for its detoxification mechanisms and also serves as a significant virulence factor for the bacterium. In this study, twelve derivatives synthesized from 5-fluoropyridine and benzo[b]thiophene demonstrated antimycobacterial efficacy with minimum inhibitory concentrations (MICs) varying between 0.5 and 32 μg/mL. Compound 2, 1-(benzo[b]thiophen-2-ylmethylene) thiosemicarbazide, emerged as the most potent candidate. It effectively inhibited Mtb KatG, enhanced the production of reactive oxygen species (ROS) in Mtb, and achieved Mtb killing within 96 hours at a concentration of 2 μg/mL (4×MIC). Molecular docking simulations revealed that compound 2 binds tightly to the active site of Mtb-KatG with a docking score of 114, indicating that it may serve as a potent inhibitor of Mtb-KatG. The rabbit skin tuberculosis model was employed to assess the virulence of Mtb. Animal study results indicated that the granulomas induced by Mtb after treatment with compound 2 were reduced in size, exhibited a lower bacterial load, and the bacteria were no longer aggregated, in contrast to those caused by untreated Mtb. Hence, compound 2 can be regarded as a molecule capable of neutralizing the virulence factors of Mtb. This research offers insights into the design of anti-Mtb molecules with novel mechanisms of action.

Differential effects of inosine monophosphate dehydrogenase (IMPDH/GuaB) inhibition in Acinetobacter baumannii and Escherichia coli

Inosine 5'-monophosphate dehydrogenase (IMPDH), known as GuaB in bacteria, catalyzes the rate-limiting step in de novo guanine biosynthesis and is conserved from humans to bacteria. We developed a series of potent inhibitors that selectively target GuaB over its human homolog. Here, we show that these GuaB inhibitors are bactericidal, generate phenotypic signatures that are distinct from other antibiotics, and elicit different time-kill kinetics and regulatory responses in two important Gram-negative pathogens: Acinetobacter baumannii and Escherichia coli. Specifically, the GuaB inhibitor G6 rapidly kills A. baumannii but only kills E. coli after 24 h. After exposure to G6, the expression of genes involved in purine biosynthesis and stress responses change in opposite directions while siderophore biosynthesis is downregulated in both species. Our results suggest that different species respond to GuaB inhibition using distinct regulatory programs and possibly explain the different bactericidal kinetics upon GuaB inhibition. The comparison highlights opportunities for developing GuaB inhibitors as novel antibiotics.IMPORTANCEA. baumannii is a priority bacterial pathogen for which development of new antibiotics is urgently needed due to the emergence of multidrug resistance. We recently developed a series of specific inhibitors against GuaB, a bacterial inosine 5'-monophosphate dehydrogenase, and achieved sub-micromolar minimum inhibitory concentrations against A. baumannii. GuaB catalyzes the rate-limiting step of de novo guanine biosynthesis and is highly conserved across bacterial pathogens. This study shows that inhibition of GuaB induced a bacterial morphological profile distinct from that of other classes of antibiotics, highlighting a novel mechanism of action. Moreover, our transcriptomic analysis showed that regulation of de novo purine biosynthesis and stress responses of A. baumannii upon GuaB inhibition differed significantly from that of E. coli.

Navigating collateral sensitivity: insights into the mechanisms and applications of antibiotic resistance trade-offs

The swift rise of antibiotic resistance, coupled with limited new antibiotic discovery, presents a significant hurdle to global public health, demanding innovative therapeutic solutions. Recently, collateral sensitivity (CS), the phenomenon in which resistance to one antibiotic increases vulnerability to another, has come to light as a potential path forward in this attempt. Targeting either unidirectional or reciprocal CS holds promise for constraining the emergence of drug resistance and notably enhancing treatment outcomes. Typically, the alteration of bacterial physiology, such as bacterial membrane potential, expression of efflux pumps, cell wall structures, and endogenous enzymatic actions, are involved in evolved collateral sensitivity. In this review, we present a thorough overview of CS in antibiotic therapy, including its definition, importance, and underlying mechanisms. We describe how CS can be exploited to prevent the emergence of resistance and enhance the results of treatment, but we also discuss the challenges and restrictions that come with implementing this practice. Our review underscores the importance of continued exploration of CS mechanisms in the broad spectrum and clinical validation of therapeutic approaches, offering insights into its role as a valuable tool in combating antibiotic resistance.

Inhibitory effect of Bacillus velezensis 1273 strain cell-free supernatant against developing and preformed biofilms of Staphylococcus aureus and MRSA

Microbial biofilms constitute a significant virulence factor and a substantial challenge in clinical environments due to their role in promoting antimicrobial resistance and their resilience to eradication efforts. Methicillin-resistant Staphylococcus aureus (MRSA) infections substantially increase healthcare costs, extend hospitalizations, and elevate morbidity and mortality rates. Therefore, developing innovative strategies to target and eliminate these bacteria and their biofilms effectively is imperative for robust epidemiological control. In this study, we evaluated the antibacterial and antibiofilm activities of cell-free supernatant (CFS) obtained from the Bacillus velezensis 1273 strain culture. Our data showed that CFS inhibited the growth of S. aureus ATCC 29213 and MRSA (clinical strain), with greater efficacy observed against S. aureus (1:16 dilution). Furthermore, CFS showed substantial potential in reducing biofilm formation in both strains (∼30 %) at subinhibitory concentrations. Additionally, the antibacterial activity against biofilm-formed cells showed that pure CFS treatment decreased the viability of S. aureus (60 %) and MRSA (45 %) sessile cells. We further demonstrated that CFS treatment induces the production of reactive oxygen species (ROS) and damages the membranes and cell walls of the pathogen cells. Genome analysis revealed the presence of genes encoding bacteriocins and secondary metabolites with antibacterial activity in the B. velezensis 1273 genome. These findings highlight the potential of probiotic bacterial metabolites as antibiofilm and anti-multidrug-resistant pathogens.

Artificial Polymerizations in Living Organisms for Biomedical Applications

Within living organisms, numerous nanomachines are constantly involved in complex polymerization processes, generating a diverse array of biomacromolecules for maintaining biological activities. Transporting artificial polymerizations from lab settings into biological contexts has expanded opportunities for understanding and managing biological events, creating novel cellular compartments, and introducing new functionalities. This review summarizes the recent advancements in artificial polymerizations, including those responding to external stimuli, internal environmental factors, and those that polymerize spontaneously. More importantly, the cutting-edge biomedical application scenarios of artificial polymerization, notably in safeguarding cells, modulating biological events, improving diagnostic performance, and facilitating therapeutic efficacy are highlighted. Finally, this review outlines the key challenges and technological obstacles that remain for polymerizations in biological organisms, as well as offers insights into potential directions for advancing their practical applications and clinical trials.

Cell Type-Specific Anti- and Pro-Oxidative Effects of Punica granatum L. Ellagitannins

Pomegranate and its by-products contain a broad spectrum of phytochemicals, such as flavonoids, phenolic acids and tannins, having pleiotropic preventive and prophylactic properties in health disorders related to oxidative stress and microbial contamination. Here, we examined the biological effects of a pomegranate peel ellagitannins-enriched (>90%) extract, PETE. In vitro studies revealed that PETE has a strong antiradical action towards synthetic radicals and biologically relevant ROS surpassing or comparable to that of Trolox. In cellular models, it showed concentration-dependent (25-100 µg/mL) yet opposing effects depending on the cell membrane type and exposure conditions. In erythrocytes, PETE protected membrane integrity in the presence of the strong oxidant HClO and restored reduced glutathione levels to up to 85% of the control value while having much weaker acute and long-term intrinsic effects. Such protection persisted even after the removal of the extract from cells, indicating strong membrane interaction. In HeLa cancer cells, and at concentrations lower than those used for red blood cells, PETE induced robust potentiation of ROS production and mitochondrial potential dissipation, leading to autophagy-like membrane morphology changes and cell death. In S. aureus, the growth arrest and bacterial death in the presence of PETE (with MIC = 31.25 µg/mL and MBC = 125 µg/mL, respectively) can be linked to the tripled ROS induction by the extract in the same concentration range. This study indicates a specificity of ROS production by the pomegranate extract depending on the type of cell, the concentration of the extract and the time of incubation. This specificity witnesses a strong potential of the extract components as candidates in antioxidant and pro-oxidant therapy.

Unveiling the Potential of CuO and Cu2O Nanoparticles against Novel Copper-Resistant Pseudomonas Strains: An In-Depth Comparison

Four novel Pseudomonas strains with record resistance to copper (Cu2+) previously isolated from ecologically diverse samples (P. lactis UKR1, P. panacis UKR2, P. veronii UKR3, and P. veronii UKR4) were tested against sonochemically synthesised copper-oxide (I) (Cu2O) and copper-oxide (II) (CuO) nanoparticles (NPs). Nanomaterials characterisation by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and High-Resolution Transmission Electron Microscopy (HRTEM) confirmed the synthesis of CuO and Cu2O NPs. CuO NPs exhibited better performance in inhibiting bacterial growth due to their heightened capacity to induce oxidative stress. The greater stability and geometrical shape of CuO NPs were disclosed as important features associated with bacterial cell toxicity. SEM and TEM images confirmed that both NPs caused membrane disruption, altered cell morphology, and pronounced membrane vesiculation, a distinctive feature of bacteria dealing with stressor factors. Finally, Cu2O and CuO NPs effectively decreased the biofilm-forming ability of the Cu2+-resistant UKR strains as well as degraded pre-established biofilm, matching NPs' antimicrobial performance. Despite the similarities in the mechanisms of action revealed by both NPs, distinctive behaviours were also detected for the different species of wild-type Pseudomonas analysed. In summary, these findings underscore the efficacy of nanotechnology-driven strategies for combating metal tolerance in bacteria.

Recent research on the physicochemical properties and biological activities of quinones and their practical applications: a comprehensive review

Quinones represent a class of crude organic compounds ubiquitously distributed in nature. Their distinctive quinone-type structure confers upon them unique properties and applications. Quinones demonstrate significant biological activities, including antioxidant, antimicrobial, and antitumor properties. Additionally, they demonstrate noteworthy physicochemical characteristics, including excellent dyeing properties and stability. Given their diverse qualities, quinones hold significant promise for applications in industrial manufacturing, healthcare, and food production, thus garnering considerable attention in recent years. While there is a growing body of research on quinones, the existing literature falls short of providing a comprehensive review encompassing recent advancements in this field along with established knowledge. This paper offers a comprehensive review of research progress for quinones, encompassing structural classification, source synthesis, extraction methods, properties, functions, and specific applications. It serves as a reference and theoretical foundation for the further development and utilization of quinones.

Reactive Oxygen Species Mediate the Bactericidal Activity of Chlorine Against Salmonella

Chlorine and its derivatives have been used as an antibacterial agent to reduce Salmonella contamination in poultry meat during processing. We evaluated the survival of 4 different Salmonella serotypes (Typhimurium, Enteritidis, Heidelberg, and Gaminara) in the presence of 50 ppm sodium hypochlorite (NaOCl) alone or with the addition of thiourea (radical scavenger) or Dip (iron chelator) to determine the contribution of reactive oxygen species (ROS) in the bactericidal activity of NaOCl. The result showed that for all four serotypes the addition of thiourea or Dip significantly increased the % survival as compared to the respective NaOCl treatment groups, while it was significantly higher with thiourea as compared to Dip (P < 0.05). We also evaluated the survival of 11 deletion mutants of S. Typhimurium, which were demonstrated to increase (∆atpC, ∆cyoA, ∆gnd, ∆nuoG, ∆pta, ∆sdhC, and ∆zwf) or decrease the production of ROS (∆edd, ∆fumB, ∆pykA, and ∆tktB) in Escherichia coli (E. coli), in the presence of 50 ppm. The results showed that only two (∆sdhC and ∆zwf) out of 7 ROS-increasing mutants showed reduced % survival as compared to the wild-type (P < 0.05), while all four deletion ROS-decreasing mutants showed significantly higher % survival as compared to the wild-type (P < 0.05). This work suggests that the production of ROS is a major component of the bactericidal activity of NaOCl against Salmonella serotypes and there might be a significant difference in the metabolic pathways involved in ROS production between Salmonella and E. coli.

Combination of aloe emodin, emodin, and rhein from Aloe with EDTA sensitizes the resistant Acinetobacter baumannii to polymyxins

Background

The continuous emergence and spread of polymyxin-resistant Acinetobacter baumannii pose a significant global health challenge, necessitating the development of novel therapeutic strategies. Aloe, with its long-standing history of medicinal use, has recently been the subject of substantial research for its efficacy against pathogenic infections.

Methods

This study investigates the potential application of anthraquinone components in aloe against polymyxin-resistant A. baumannii by liquid chromatography-mass spectrometry, in vitro activity assessment, and construction of animal infection models.

Results

The findings demonstrate that aloe emodin, emodin, rhein, and their mixtures in equal mass ratios (EAR) exhibit strain-specific antibacterial activities against polymyxin-resistant A. baumannii. Co-administration of EAR with EDTA synergistically and universally enhanced the antibacterial activity and bactericidal efficacy of polymyxins against polymyxin-resistant A. baumannii, while also reducing the frequency of polymyxin-resistant mutations in polymyxinssensitive A. baumannii. Following toxicity assessment on human hepatic and renal cell lines, the combination therapy was applied to skin wounds in mice infected with polymyxin-resistant A. baumannii. Compared to monotherapy, the combination therapy significantly accelerated wound healing and reduced bacterial burden.

Conclusions

The combination of EAR and EDTA with polymyxins offers a novel therapeutic approach for managing skin infections caused by polymyxinresistant A. baumannii.

BD Vacutainer™ Urine Culture & Sensitivity Preservative PLUS Plastic Tubes Minimize the Harmful Impact of Stressors Dependent on Temperature and Time Storage in Uropathogenic Bacteria

Background: Urinary tract infection is a worldwide health problem. According to the Clinical Laboratory Improvement Amendments and the European Urinalysis Guideline, urine samples should be tested within 2 h of collection. Thus, using chemical preservatives that guarantee the pre-analytical conditions is a practical tool. However, the effects of temperature and storage time as uropathogenic bacteria stressors are unclear. Methods: Gram-negative and -positive ATTC strains, E. coli, P. mirabilis, E. faecalis, and S. aureus, were used in this study. Strains in liquid media were stored at 4, 25, and 37 °C for 0, 2, 12, 24, and 48 h in tubes with and without preservatives. Then, reactive oxygen species (ROS) levels, viable but non-culturable bacteria (VBNC), and bacteria growth were analyzed. Results: A high ROS level was associated with the presence of VBNC and dead bacteria with low CFU counts, but a low ROS level increased the CFU number, depending on temperature and storage time in tubes without preservatives (boric acid, sodium borate, and formate). The BD Vacutainer™ Urine Culture & Sensitivity Preservative PLUS Plastic Tubes (C&S-PP) prevent this ROS increase, maintaining the CFU number for longer. Conclusions: C&S-PP tubes minimize the stressor effects (temperature and time storage) on uropathogenic bacteria when stored, improving the pre-analytical conditions of cultures realized by the clinical laboratory.

Reaction-Induced Self-Assembly of Polymyxin Mitigates Cytotoxicity and Reverses Drug Resistance

Polymyxins have been regarded as an efficient therapeutic against many life-threatening, multidrug resistant Gram-negative bacterial infections; however, the cytotoxicity and emergence of drug resistance associated with polymyxins have greatly hindered their clinical potential. Herein, the reaction-induced self-assembly (RISA) of polymyxins and natural aldehydes in aqueous solution is presented. The resulting assemblies effectively mask the positively charged nature of polymyxins, reducing their cytotoxicity. Moreover, the representative PMBA4 (composed of polymyxin B (PMB) and (E)-2-heptenal (A4)) assemblies demonstrate enhanced binding to Gram-negative bacterial outer membranes and exhibit multiple antimicrobial mechanisms, including increased membrane permeability, elevated bacterial metabolism, suppression of quorum sensing, reduced ATP synthesis, and potential reduction of bacterial drug resistance. Remarkably, PMBA4 assemblies reverse drug resistance in clinically isolated drug-resistant strains of Gram-negative bacteria, demonstrating exceptional efficacy in preventing and eradicating bacterial biofilms. PMBA4 assemblies efficiently eradicate Gram-negative bacterial biofilm infections in vivo and alleviate inflammatory response. This RISA strategy offers a practical and clinically applicable approach to minimize side effects, reverse drug resistance, and prevent the emergence of resistance associated with free polymyxins.

Development of an effective meropenem/KPC-2 inhibitor combination to combat infections caused by carbapenem-resistant Klebsiella pneumoniae

The global public health threat of antibiotic resistance continues to escalate, and necessitates the implementation of urgent measures to expand the arsenal of antimicrobial drugs. This study identified a benzoxaborane compound, namely 5-chloro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole (AN2178), which can inhibit the catalytic activity of the Klebsiella pneumoniae carbapenemase (KPC-2) enzyme effectively. The efficacy of AN2718 as an inhibitor for the KPC-2 enzyme was verified through various assays, including enzyme activity assays and isothermal titration calorimetry. Results of multiple biochemical assays, minimum inhibitory concentration assays and time-killing assays also showed that binding of AN2718 to KPC-2 enabled restoration of the bactericidal effect of meropenem. The survival rate of mice infected with carbapenem-resistant, high-virulence strains increased significantly upon treatment with AN2718. Most importantly, the meropenem and AN2718 combination was effective on KPC-2 mutations such as KPC-33, which evolved clinically and exhibited resistance to ceftazidime-avibactam after clinical use for a couple of years. Comprehensive safety tests both in vitro and in vivo, such as cytotoxicity, haemolytic activity and cytochrome P450 inhibition assays, demonstrated that AN2718 was safe for clinical use. These promising data indicate that AN2718 has high potential for approval for the treatment of drug resistant-bacterial infections, including those caused by ceftazidime-avibactam-resistant strains. AN2718 can be regarded as a valuable addition to the current antimicrobial armamentarium, and a promising tool to combat antimicrobial resistance.

Fabrication of PTFE + TiO2/Ag coatings on 316L/polydopamine with advanced mechanical, bio-corrosion, and antibacterial properties for stainless steel Catheters

This study explores the corrosion resistance and antibacterial properties of a PTFE + TiO2/Ag coating applied to 316 L stainless steel. To enhance adhesion, a polydopamine interlayer was chemically deposited onto the steel surface. The PTFE + TiO2 coating was subsequently applied through immersion, followed by the deposition of silver nanoparticles using a chemical method. Optimization of the polydopamine interlayer involved varying temperature, time, stirring speed, and drying parameters. The optimal conditions for the polydopamine interlayer were determined to be 60 °C for 1 h, 300 rpm stirring, and 24-h drying in a freeze dryer. Analytical results demonstrated that both the PTFE + TiO2 and PTFE/PTFE + TiO2/Ag coatings exhibited exceptional corrosion resistance, with corrosion currents of 3.3 × 10-5 and 3.2 × 10-4 μA/cm2, respectively. Antibacterial assessments showcased the remarkable ability of the PTFE/PTFE + TiO2/Ag coating, containing 5% silver content, to effectively inhibit bacterial penetration within a 6.5 mm radius. Furthermore, this coating displayed a water contact angle of 143°, classifying it as a hydrophobic coating. The photocatalytic efficiency (Rs) was determined to be 3.18 × 10-3 A/W, a performance level comparable to that of a standard UV sensor. These findings underscore the substantial enhancements in corrosion resistance, antibacterial performance, and hydrophobic characteristics achieved with the PTFE + TiO2/Ag coating, particularly through the novel optimization of the polydopamine interlayer. This coating exhibits great promise for multifunctional protective applications in diverse fields, particularly demonstrating its suitability for implants and bio-coatings.

Ligand-Receptor Interaction-Induced Intracellular Phase Separation: A Global Disruption Strategy for Resistance-Free Lethality of Pathogenic Bacteria

Addressing the global challenge of bacterial resistance demands innovative approaches, among which multitargeting is a widely used strategy. Current strategies of multitargeting, typically achieved through drug combinations or single agents inherently aiming at multiple targets, face challenges such as stringent pharmacokinetic and pharmacodynamic requirements and cytotoxicity concerns. In this report, we propose a bacterial-specific global disruption approach as a vastly expanded multitargeting strategy that effectively disrupts bacterial subcellular organization. This effect is achieved through a pioneering chemical design of ligand-receptor interaction-induced aggregation of small molecules, i.e., DNA-induced aggregation of a diarginine peptidomimetic within bacterial cells. These intracellular aggregates display affinity toward various proteins and thus substantially interfere with essential bacterial functions and rupture bacterial cell membranes in an "inside-out" manner, leading to robust antibacterial activities and suppression of drug resistance. Additionally, biochemical analysis of macromolecule binding affinity, cytoplasmic localization patterns, and bacterial stress responses suggests that this bacterial-specific intracellular aggregation mechanism is fundamentally different from nonselective classic DNA or membrane binding mechanisms. These mechanistic distinctions, along with the peptidomimetic's selective permeation of bacterial membranes, contribute to its favorable biocompatibility and pharmacokinetic properties, enabling its in vivo antimicrobial efficacy in several animal models, including mice-based superficial wound models, subcutaneous abscess models, and septicemia infection models. These results highlight the great promise of ligand-receptor interaction-induced intracellular aggregation in achieving a globally disruptive multitargeting effect, thereby offering potential applications in the treatment of malignant cells, including pathogens, tumor cells, and infected tissues.

Assessment of biodegradation and toxicity of alternative plasticizer di(2-ethylhexyl) terephthalate: Impacts on microbial biofilms, metabolism, and reactive oxygen species-mediated stress response

Although di(2-ethylhexyl) terephthalate (DOTP) is being widely adopted as a non-phthalate plasticizer, existing research primarily focuses on human and rat toxicity. This leaves a significant gap in our understanding of their impact on microbial communities. This study assessed the biodegradation and toxicity of DOTP on microbes, focusing on its impact on biofilms and microbial metabolism using Rhodococcus ruber as a representative bacterial strain. DOTP is commonly found in mass fractions between 0.6 and 20% v/v in various soft plastic products. This study used polyvinyl chloride films (PVC) with varying DOTP concentrations (range 1-10% v/v) as a surface for analysis of biofilm growth. Cell viability and bacterial stress responses were tested using LIVE/DEAD™ BacLight™ Bacterial Viability Kit and by the detection of reactive oxygen species using CellROX™ Green Reagent, respectively. An increase in the volume of dead cells (in the plastisphere biofilm) was observed with increasing DOTP concentrations in experiments using PVC films, indicating the potential negative impact of DOTP on microbial communities. Even at a relatively low concentration of DOTP (1%), signs of stress in the microbes were noticed, while concentrations above 5% compromised their ability to survive. This research provides a new understanding of the environmental impacts of alternative plasticizers, prompting the need for additional research into their wider effects on both the environment and human health.

A review of metallic nanoparticles: present issues and prospects focused on the preparation methods, characterization techniques, and their theranostic applications

Metallic nanoparticles (MNPs) have garnered significant attention due to their ability to improve the therapeutic index of medications by reducing multidrug resistance and effectively delivering therapeutic agents through active targeting. In addition to drug delivery, MNPs have several medical applications, including in vitro and in vivo diagnostics, and they improve the biocompatibility of materials and nutraceuticals. MNPs have several advantages in drug delivery systems and genetic manipulation, such as improved stability and half-life in circulation, passive or active targeting into the desired target selective tissue, and gene manipulation by delivering genetic materials. The main goal of this review is to provide current information on the present issues and prospects of MNPs in drug and gene delivery systems. The current study focused on MNP preparation methods and their characterization by different techniques, their applications to targeted delivery, non-viral vectors in genetic manipulation, and challenges in clinical trial translation.

Untangling the adaptive strategies of thermophilic bacterium Anoxybacillus rupiensis TPH1 under low temperature

The present study investigates the low temperature tolerance strategies of thermophilic bacterium Anoxybacillus rupiensis TPH1, which grows optimally at 55 °C , by subjecting it to a temperature down-shift of 10 °C (45 °C) for 4 and 6 h followed by studying its growth, morphophysiological, molecular and proteomic responses. Results suggested that although TPH1 experienced increased growth inhibition, ROS production, protein oxidation and membrane disruption after 4 h of incubation at 45 °C yet maintained its DNA integrity and cellular structure through the increased expression of DNA damage repair and cell envelop synthesizing proteins and also progressively alleviated growth inhibition by 20% within two hours i.e., 6 h, by inducing the expression of antioxidative enzymes, production of unsaturated fatty acids, capsular and released exopolysaccharides and forming biofilm along with chemotaxis proteins. Conclusively, the adaptation of Anoxybacillus rupiensis TPH1 to lower temperature is mainly mediated by the synthesis of large numbers of defense proteins and exopolysaccharide rich biofilm formation.

Synthesis of Carbon Dots via Microwave-Assisted Process: Specific Sensing of Fe(III) and Antibacterial Activity

Carbon dots synthesized from a renewable and sustainable source of biomass have greater attention in the nanomaterial research field. In the present study, we adopted a facile and green synthesis of carbon dots from bio waste of pumpkin seeds using a one-pot microwave-assisted carbonization method. The synthesized carbon dots exhibit excellent photoluminescence properties with a bright blue emission peak at 399 nm and fluorescence quantum yield was about 9.5%. The optical properties and structure of carbon dots were examined using various spectroscopy techniques and the synthesized carbon practical size was about 4.37 nm and possessed good solubility in water. Carbon dots were used for the detection of Ferric ions in the water bodies and the interaction between Fe3+ ions and carbon dots was evaluated by fluorescence spectroscopy techniques. This method is a simple and selective detection of Fe3+ in the aqueous medium. Interestingly carbon dots also show good antibacterial activity at a very low concentration (1 mg/L) for effective control of E. coli 93% and Pseudomonas aeruginosa (81%), within 12 h.

Antioxidants are ineffective at quenching reactive oxygen species inside bacteria and should not be used to diagnose oxidative stress

A wide variety of stresses have been proposed to exert killing effects upon bacteria by stimulating the intracellular formation of reactive oxygen species (ROS). A key part of the supporting evidence has often been the ability of antioxidant compounds to protect the cells. In this study, some of the most-used antioxidants-thiourea, glutathione, N-acetylcysteine, and ascorbate-have been examined. Their ability to quench superoxide and hydrogen peroxide was verified in vitro, but the rate constants were orders of magnitude too slow for them to have an impact upon superoxide and peroxide concentrations in vivo, where these species are already scavenged by highly active enzymes. Indeed, the antioxidants were unable to protect the growth and ROS-sensitive enzymes of E. coli strains experiencing authentic oxidative stress. Similar logic posits that antioxidants cannot substantially quench hydroxyl radicals inside cells, which contain abundant biomolecules that react with them at diffusion-limited rates. Indeed, antioxidants were able to protect cells from DNA damage only if they were applied at concentrations that slow metabolism and growth. This protective effect was apparent even under anoxic conditions, when ROS could not possibly be involved, and it was replicated when growth was similarly slowed by other means. Experimenters should discard the use of antioxidants as a way of detecting intracellular oxidative stress and should revisit conclusions that have been based upon such experiments. The notable exception is that these compounds can effectively degrade hydrogen peroxide from environmental sources before it enters cells.

Metabolomics analysis of the lactobacillus plantarum ATCC 14917 response to antibiotic stress

BACKGROUND

Lactobacillus plantarum has been found to play a significant role in maintaining the balance of intestinal flora in the human gut. However, it is sensitive to commonly used antibiotics and is often incidentally killed during treatment. We attempted to identify a means to protect L. plantarum ATCC14917 from the metabolic changes caused by two commonly used antibiotics, ampicillin, and doxycycline. We examined the metabolic changes under ampicillin and doxycycline treatment and assessed the protective effects of adding key exogenous metabolites.

RESULTS

Using metabolomics, we found that under the stress of ampicillin or doxycycline, L. plantarum ATCC14917 exhibited reduced metabolic activity, with purine metabolism a key metabolic pathway involved in this change. We then screened the key biomarkers in this metabolic pathway, guanine and adenosine diphosphate (ADP). The exogenous addition of each of these two metabolites significantly reduced the lethality of ampicillin and doxycycline on L. plantarum ATCC14917. Because purine metabolism is closely related to the production of reactive oxygen species (ROS), the results showed that the addition of guanine or ADP reduced intracellular ROS levels in L. plantarum ATCC14917. Moreover, the killing effects of ampicillin and doxycycline on L. plantarum ATCC14917 were restored by the addition of a ROS accelerator in the presence of guanine or ADP.

CONCLUSIONS

The metabolic changes of L. plantarum ATCC14917 under antibiotic treatments were determined. Moreover, the metabolome information that was elucidated can be used to help L. plantarum cope with adverse stress, which will help probiotics become less vulnerable to antibiotics during clinical treatment.

Plant-mediated synthesis of Mn3O4nanoparticles: challenges and applications

This review focuses on the green synthesis methods, challenges, and applications of manganese oxide (Mn3O4) nanoparticles investigated in the past five years. Mn3O4nanoparticles offer some unique properties that are attributed in part to the presence of mixed oxidation states of manganese (i.e. +2 and +3) in the particle, which can be utilized in a wide range of redox-sensitive applications, such as in developing supercapacitive energy storage materials. In addition, the green synthesis of Mn3O4nanoparticles through plant extracts has potential uses in sustainable nanotechnology. Various plant extract-mediated synthesis techniques for Mn3O4nanoparticles have been investigated and presented. By comparing the size and structure of the synthesized Mn3O4nanoparticles, we have observed a consistent pattern of obtaining spherical particles with a size ranging from 16 to 50 nm. The morphology of the generated Mn3O4nanoparticles can be influenced by the annealing temperature and the composition of the plant extract used during the nanoparticle synthesis. Additionally, numerous applications for the greenly produced Mn3O4nanoparticles have been demonstrated. Mn3O4nanoparticles derived from plant extracts have been found to possess antimicrobial properties, supercapacitive and electrochemical capabilities, and excellent pollutant degradation efficiency. However, the magnetic properties of these nanoparticles synthesized by plant extracts are yet to be explored for potential biomedical applications. Finally, challenges to existing synthetic methods and future perspectives on the potential applications of these green synthesized Mn3O4nanoparticles are highlighted.

Genome-scale model of Rothia mucilaginosa predicts gene essentialities and reveals metabolic capabilities

Cystic fibrosis (CF), an inherited genetic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator gene, results in sticky and thick mucosal fluids. This environment facilitates the colonization of various microorganisms, some of which can cause acute and chronic lung infections, while others may positively impact the disease. Rothia mucilaginosa, an oral commensal, is relatively abundant in the lungs of CF patients. Recent studies have unveiled its anti-inflammatory properties using in vitro three-dimensional lung epithelial cell cultures and in vivo mouse models relevant to chronic lung diseases. Apart from this, R. mucilaginosa has been associated with severe infections. However, its metabolic capabilities and genotype-phenotype relationships remain largely unknown. To gain insights into its cellular metabolism and genetic content, we developed the first manually curated genome-scale metabolic model, iRM23NL. Through growth kinetics and high-throughput phenotypic microarray testings, we defined its complete catabolic phenome. Subsequently, we assessed the model's effectiveness in accurately predicting growth behaviors and utilizing multiple substrates. We used constraint-based modeling techniques to formulate novel hypotheses that could expedite the development of antimicrobial strategies. More specifically, we detected putative essential genes and assessed their effect on metabolism under varying nutritional conditions. These predictions could offer novel potential antimicrobial targets without laborious large-scale screening of knockouts and mutant transposon libraries. Overall, iRM23NL demonstrates a solid capability to predict cellular phenotypes and holds immense potential as a valuable resource for accurate predictions in advancing antimicrobial therapies. Moreover, it can guide metabolic engineering to tailor R. mucilaginosa's metabolism for desired performance.IMPORTANCECystic fibrosis (CF) is a genetic disorder characterized by thick mucosal secretions, leading to chronic lung infections. Rothia mucilaginosa is a common bacterium found in various parts of the human body, acting as a normal part of the flora. In people with weakened immune systems, it can become an opportunistic pathogen, while it is prevalent and active in CF airways. Recent studies have highlighted its anti-inflammatory properties in the lower pulmonary system, indicating the intricate relationship between microbes and human health. Herein, we have developed the first manually curated metabolic model of R. mucilaginosa. Our study examined the previously unknown relationships between the bacterium's genotype and phenotype and identified essential genes that impact the metabolism under various conditions. With this, we opt for paving the way for developing new strategies in antimicrobial therapy and metabolic engineering, leading to enhanced therapeutic outcomes in cystic fibrosis and related conditions.

Bacterial Surface Appendages Modulate the Antimicrobial Activity Induced by Nanoflake Surfaces on Titanium

Bioinspired nanotopography is a promising approach to generate antimicrobial surfaces to combat implant-associated infection. Despite efforts to develop bactericidal 1D structures, the antibacterial capacity of 2D structures and their mechanism of action remains uncertain. Here, hydrothermal synthesis is utilized to generate two 2D nanoflake surfaces on titanium (Ti) substrates and investigate the physiological effects of nanoflakes on bacteria. The nanoflakes impair the attachment and growth of Escherichia coli and trigger the accumulation of intracellular reactive oxygen species (ROS), potentially contributing to the killing of adherent bacteria. E. coli surface appendages type-1 fimbriae and flagella are not implicated in the nanoflake-mediated modulation of bacterial attachment but do influence the bactericidal effects of nanoflakes. An E. coli ΔfimA mutant lacking type-1 fimbriae is more susceptible to the bactericidal effects of nanoflakes than the parent strain, while E. coli cells lacking flagella (ΔfliC) are more resistant. The results suggest that type-1 fimbriae confer a cushioning effect that protects bacteria upon initial contact with the nanoflake surface, while flagella-mediated motility can lead to elevated membrane abrasion. This finding offers a better understanding of the antibacterial properties of nanoflake structures that can be applied to the design of antimicrobial surfaces for future medical applications.

Ultrastructural and morphological studies on variables affecting Escherichia coli with selected commercial antibiotics

Background

Many studies reported the effects of antibiotic exposure on E. coli bacterial growth and cell modification. However, scarce descriptive information on ultrastructural effects upon exposure of commercial antibiotics.

Methods

This study described the morphological and ultrastructural alterations caused by selected antibiotics (amoxicillin-clavulanate, ceftriaxone, polymyxin B, colistin, gentamicin, and amikacin) that targeted cell wall, plasma membrane, and cytoplasmic density, and also proteins synthesis. We determined extracellular morphological changes of exposure through scanning electron microscopy (FESEM) and intracellular activities through transmission electron microscopy (TEM) investigation.

Results

FESEM and TEM micrograph of E. coli exposed with selected antibiotics shows ultrastructural changes in beta-lactam class (amoxicillin-clavulanate, ceftriaxone) elongated the cells as the cell wall was altered as it inhibits bacterial cell wall synthesis, polymyxin class (polymyxin B, colistin) had plasmid and curli-fimbriae as it breaking down the plasma/cytoplasmic membrane, and aminoglycoside class (gentamicin, and amikacin) reduced ribosome concentration as it inhibits bacterial protein synthesis by binding to 30 s ribosomes.

Conclusion

Morphological and ultrastructural alterations of E. coli's mechanism of actions were translated and depicted. This study could be reference for characterization studies for morphological and ultrastructural of E. coli upon exposure to antimicrobial agents.