TiO2 photoexcitation promoted horizontal transfer of resistance genes mediated by phage transduction

How micro-/nano-plastics influence the horizontal transfer of antibiotic resistance genes - A review

Plastic debris such as microplastics (MPs) and nanoplastics (NPTs), along with antibiotic resistance genes (ARGs), are pervasive in the environment and are recognized as significant global health and ecological concerns. Micro-/nano-plastics (MNPs) have been demonstrated to favor the spread of ARGs by enhancing the frequency of horizontal gene transfer (HGT) through various pathways. This paper comprehensively and systematically reviews the current study with focus on the influence of plastics on the HGT of ARGs. The critical role of MNPs in the HGT of ARGs has been well illustrated in sewage sludge, livestock farms, constructed wetlands and landfill leachate. A summary of the performed HGT assay and the underlying mechanism of plastic-mediated transfer of ARGs is presented in the paper. MNPs could facilitate or inhibit HGT of ARGs, and their effects depend on the type, size, and concentration. This review provides a comprehensive insight into the effects of MNPs on the HGT of ARGs, and offers suggestions for further study. Further research should attempt to develop a standard HGT assay and focus on investigating the impact of different plastics, including the oligomers they released, under real environmental conditions on the HGT of ARGs.

Engineered nanomaterials exert sublethal bacterial stress at very low doses: Effects of concentration, light, and media on cell membrane permeability

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 chemical 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.

Silver nanoparticles facilitate phage-borne resistance gene transfer in planktonic and microplastic-attached bacteria

The spread of bacteriophage-borne antibiotic resistance genes (ARGs) poses a realistic threat to human health. Nanomaterials, as important emerging pollutants, have potential impacts on ARGs dissemination in aquatic environments. However, little is known about its role in transductive transfer of ARGs mediated by bacteriophage in the presence of microplastics. Therefore, this study comprehensively investigated the influence of silver nanoparticles (AgNPs) on the transfer of bacteriophage-encoded ARGs in planktonic Escherichia coli and microplastic-attached biofilm. AgNPs exposure facilitated the phage transduction in planktonic and microplastic-attached bacteria at ambient concentration of 0.1 mg/L. Biological binding mediated by phage-specific recognition, rather than physical aggregation conducted by hydrophilicity and ζ-potential, dominated the bacterial adhesion of AgNPs. The aggregated AgNPs in turn resulted in elevated oxidative stress and membrane destabilization, which promoted the bacteriophage infection to planktonic bacteria. AgNPs exposure could disrupt colanic acid biosynthesis and then reduce the thickness of biofilm on microplastics, contributing to the transfer of phage-encoded ARGs. Moreover, the roughness of microplastics also affected the performance of AgNPs on the transductive transfer of ARGs in biofilms. This study reveals the compound risks of nanomaterials and microplastics in phage-borne ARGs dissemination and highlights the complexity in various environmental scenarios.

Comprehensive insights into antibiotic resistance gene migration in microalgal-bacterial consortia: Mechanisms, factors, and perspectives

With the overuse of antibiotics, antibiotic resistance gene (ARG) prevalence is gradually increasing. ARGs are considered emerging contaminants that are broadly concentrated and dispersed in most aquatic environments. Recently, interest in microalgal-bacterial biotreatment of antibiotics has increased, as eukaryotes are not the primary target of antimicrobial drugs. Moreover, research has shown that microalgal-bacterial consortia can minimize the transmission of antibiotic resistance in the environment. Unfortunately, reviews surrounding the ARG migration mechanism in microalgal-bacterial consortia have not yet been performed. This review briefly introduces the migration of ARGs in aquatic environments. Additionally, an in-depth summary of horizontal gene transfer (HGT) between cyanobacteria and bacteria and from bacteria to eukaryotic microalgae is presented. Factors influencing gene transfer in microalgal-bacterial consortia are discussed systematically, including bacteriophage abundance, environmental conditions (temperature, pH, and nutrient availability), and other selective pressure conditions including nanomaterials, heavy metals, and pharmaceuticals and personal care products. Furthermore, considering that quorum sensing could be involved in DNA transformation by affecting secondary metabolites, current knowledge surrounding quorum sensing regulation of HGT of ARGs is summarized. In summary, this review gives valuable information to promote the development of practical and innovative techniques for ARG removal by microalgal-bacterial consortia.

Augmented dissemination of antibiotic resistance elicited by non-antibiotic factors

The emergence and rapid spread of antibiotic resistance seriously compromise the clinical efficacy of current antibiotic therapies, representing a serious public health threat worldwide. Generally, drug-susceptible bacteria can acquire antibiotic resistance through genetic mutation or gene transfer, among which horizontal gene transfer (HGT) plays a dominant role. It is widely acknowledged that the sub-inhibitory concentrations of antibiotics are the key drivers in promoting the transmission of antibiotic resistance. However, accumulating evidence in recent years has shown that in addition to antibiotics, non-antibiotics can also accelerate the horizontal transfer of antibiotic resistance genes (ARGs). Nevertheless, the roles and potential mechanisms of non-antibiotic factors in the transmission of ARGs remain largely underestimated. In this review, we depict the four pathways of HGT and their differences, including conjugation, transformation, transduction and vesiduction. We summarize non-antibiotic factors accounting for the enhanced horizontal transfer of ARGs and their underlying molecular mechanisms. Finally, we discuss the limitations and implications of current studies.

Nonsteroidal anti-inflammatory drug diclofenac accelerates the emergence of antibiotic resistance via mutagenesis

Overuse of antimicrobial agents are generally considered to be a key factor in the occurrence of antibiotic resistance bacteria (ARB). Nevertheless, it is unclear whether ARB can be induced by non-antibiotic chemicals such as nonsteroidal anti-inflammatory drug (NSAID). Thus, the objective of this study is to investigate whether NSAID diclofenac (DCF) promote the emergence of antibiotic resistance in Escherichia coli K12 MG1655. Our results suggested that DCF induced the occurrence of ARB which showed hereditary stability of resistance. Meanwhile, gene variation was identified on chromosome of the ARB, and DCF can cause bacterial oxidative stress and SOS response. Subsequently, transcriptional levels of antioxidant (soxS, sodA, sodC, gor, katG, ahpF) and SOS (recA, lexA, uvrA, uvrB, ruvA, ruvB, dinB, umuC, polB) system-related genes were enhanced. However, the expression of related genes cannot be increased in high-dosage treatment compared with low-dosage samples because of cytotoxicity and cellular damage. Simultaneously, high-dosage DCF decreased the mutation frequency but enhanced the resistance of mutants. Our findings expand our knowledge of the promoting effect on the emergence of ARB caused by DCF. More attention and regulations should be given to these potential ecological and health risks for widespread DCF.

Metal-based nanomaterials as antimicrobial agents: A novel driveway to accelerate the aggravation of antibiotic resistance

The consequences of antibiotic tolerance directly affect human health and result in socioeconomic loss. Nanomaterials as antimicrobial agents are considered a promising alternative to antibiotics and have been blended with various medical applications. However, with increasing evidence that metal-based nanomaterials may induce antibiotic tolerance, there is an urgent need to scrutinize how nanomaterial-induced microbial adaption affects the evolution and spread of antibiotic tolerance. Accordingly, within this investigation, we summarized the principal factors influencing the resistance development exposed to metal-based nanomaterials, including physicochemical properties, exposure scenario, as well as bacterial response. Furthermore, the mechanisms of metal-based nanomaterial-induced antibiotic resistance development were comprehensively elucidated from acquired resistance by horizontal transfer of antibiotic resistance genes (ARGs), intrinsic resistance by genetic mutation or upregulated resistance-related gene expression, and adaptive resistance by global evolution. Overall, our review raises concerns about the safety of nanomaterials as antimicrobial agents, which will facilitate assistance in the safe development of antibiotic-free antibacterial strategies.

The significance of metallic nanoparticles in the emerging, development and spread of antibiotic resistance

An ever-increasing number of newly synthesised nanoparticles have a constantly expanding range of applications. The large-scale implementation of nanoparticles will inevitably lead to intentional or accidental contamination of various environments. Since the major benefit of using several metallic nanoparticles is antimicrobial activity, these emerging contaminants may have a potentially hazardous impact on the development and spread of antibiotic resistance - a challenge that threats infection therapy worldwide. Few studies underline that metallic nanoparticles may affect the emergence and evolution of resistance via mutations and horizontal transfer between different bacterial species. Due to the complexity of factors and mechanisms involved in disseminating antibiotic resistance, it is crucial to investigate if metallic nanoparticles play a significant role in this process through co-selection ability and pressure exerted on bacteria. The aim of this review is to summarise the current research on mutations and three main horizontal gene transfer modes facilitated by nanoparticles. Here, the current results in the field are presented, major knowledge gaps and the necessity for more environmentally relevant studies are discussed.

Nanoparticle Impact on the Bacterial Adaptation: Focus on Nano-Titania

Titanium dioxide nanoparticles (nano-titania/TiO₂ NPs) are used in different fields and applications. However, the release of TiO₂ NPs into the environment has raised concerns about their biosafety and biosecurity. In light of the evidence that TiO₂ NPs could be used to counteract antibiotic resistance, they have been investigated for their antibacterial activity. Studies reported so far indicate a good performance of TiO₂ NPs against bacteria, alone or in combination with antibiotics. However, bacteria are able to invoke multiple response mechanisms in an attempt to adapt to TiO₂ NPs. Bacterial adaption arises from global changes in metabolic pathways via the modulation of regulatory networks and can be related to single-cell or multicellular communities. This review describes how the impact of TiO₂ NPs on bacteria leads to several changes in microorganisms, mainly during long-term exposure, that can evolve towards adaptation and/or increased virulence. Strategies employed by bacteria to cope with TiO₂ NPs suggest that their use as an antibacterial agent has still to be extensively investigated from the point of view of the risk of adaptation, to prevent the development of resistance. At the same time, possible effects on increased virulence following bacterial target modifications by TiO₂ NPs on cells or tissues have to be considered.

Performance and mechanisms exploration of nano zinc oxide (nZnO) on anaerobic decolorization by Shewanella oneidensis MR-1

Although the ecological safety of nanomaterials is of widespread concern, their current ambient concentrations are not yet sufficient to cause serious toxic effects. Thus, the nontoxic bioimpact of nanomaterials in wastewater treatment has attracted increasing attention. In this study, the effect of nano zinc oxide (nZnO), one of the most widely used nanomaterials, on the anaerobic biodegradation of methyl orange (MO) by Shewanella oneidensis MR-1 was comprehensively investigated. High-dosage nZnO (>0.5 mg/L) caused severe toxic stress on S. oneidensis MR-1, resulting in the decrease in decolorization efficiency. However, nZnO at ambient concentrations could act as nanostimulants and promote the anaerobic removal of MO by S. oneidensis MR-1, which should be attributed to the improvement of decolorization efficiency rather than cell proliferation. The dissolved Zn²⁺ was found to contribute to the bioeffect of nZnO on MO decolorization. Further investigation revealed that low-dosage nZnO could promote the cell viability, membrane permeability, anaerobic metabolism, as well as related gene expression, indicating that nZnO facilitated rather than inhibited the anaerobic wastewater treatment under ambient conditions. Thus, this work provides a new insight into the bioeffect of nZnO in actual environment and facilitates the practical application of nanomaterials as nanostimulants in biological process.

How multi-walled carbon nanotubes in wastewater influence the fate of coexisting antibiotic resistant genes in the subsequent disinfection process

Wastewater treatment plants (WWTPs) are important hubs for the spread of antibiotic resistance genes (ARGs). Engineered nanoparticles, which was inevitably released to WWTPs, could change environmentally sensitive of antibiotic resistant bacteria (ARB). This would influence the fate of ARGs in subsequent disinfection process and consequent health risk. In this study, the ARGs fate of the effluent in conventional sodium hypochlorite (NaClO) disinfection process was investigated as multi-walled carbon nanotubes (MWCNTs) existed in sequencing batch reactor (SBR). The results showed the existence of MWCNTs in SBR could enhance the removal efficiency of intracellular 16S rRNA gene and intI1, extracellular intI1, sul2 and tetX in the effluent by NaClO. This is mainly due to the variation of bacterial physiological status, bacterial population structure and the activation of NaClO under the role of MWCNTs. MWCNTs in SBR could increase in membrane permeability of bacterial cells, which would be conducive to the penetration of chlorination to cytoplasm. MWCNTs in SBR also could change the bacterial population structure and induce the chlorine-sensitive bacteria; thus the potential hosts of ARGs in the effluent would be more easily inactivated by NaClO. Moreover, the residual MWCNTs in the effluent could activate NaClO to generate various free radical, which would enhance the oxidizing capacity of chlorination.

Detection and various environmental factors of antibiotic resistance gene horizontal transfer

Bacterial antibiotic resistance in water environments is becoming increasingly severe, and new antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have also attracted the attention of researchers. The horizontal transfer of ARGs in water environments is considered one of the main sources of bacterial resistance in the natural environment. Horizontal gene transfer (HGT) mainly includes conjugation, natural transformation, and transduction, and conjugation has been investigated most. Several studies have shown that there are a large number of environmental factors that might affect the horizontal transfer of ARGs in water environments, such as nanomaterials, various oxidants, and light; however, there is still a lack of systematic and comprehensive reviews on the detection and the effects of the influence factors of on ARG horizontal transfer. Therefore, this study introduced three HGT modes, analysed the advantages and disadvantages of current methods for monitoring HGT, and then summarized the influence and mechanism of various factors on ARG horizontal transfer, and the possible reasons for the different effects caused by similar factors were mainly critically discussed. Finally, existing research deficiencies and future research directions of ARG horizontal transfer in water environments were discussed.

Bacteriophages: Underestimated vehicles of antibiotic resistance genes in the soil

Bacteriophages (phages), the most abundant biological entities on Earth, have a significant effect on the composition and dynamics of microbial communities, biogeochemical cycles of global ecosystems, and bacterial evolution. A variety of antibiotic resistance genes (ARGs) have been identified in phage genomes in different soil samples. Phages can mediate the transfer of ARGs between bacteria via transduction. Recent studies have suggested that anthropogenic activities promote phage-mediated horizontal gene transfer events. Therefore, the role of phages in the dissemination of ARGs, which are a potential threat to human health, may be underestimated. However, the contribution of phages to the transfer of ARGs is still poorly understood. Considering the growing and wide concerns of antibiotic resistance, phages should be considered a research focus in the mobile resistome. This review aimed to provide an overview of phages as vehicles of ARGs in soil. Here, we summarized the current knowledge on the diversity and abundance of ARGs in soilborne phages and analyzed the contribution of phages to the horizontal transfer of ARGs. Finally, research deficiencies and future perspectives were discussed. This study provides a reference for preventing and controlling ARG pollution in agricultural systems.

Safer plant-based nanoparticles for combating antibiotic resistance in bacteria: A comprehensive review on its potential applications, recent advances, and future perspective

BACKGROUND

Antibiotic resistance is one of the current threats to human health, forcing the use of drugs that are more noxious, costlier, and with low efficiency. There are several causes behind antibiotic resistance, including over-prescription of antibiotics in both humans and livestock. In this scenario, researchers are shifting to new alternatives to fight back this concerning situation.

SCOPE AND APPROACH

Nanoparticles have emerged as new tools that can be used to combat deadly bacterial infections directly or indirectly to overcome antibiotic resistance. Although nanoparticles are being used in the pharmaceutical industry, there is a constant concern about their toxicity toward human health because of the involvement of well-known toxic chemicals (i.e., sodium/potassium borohydride) making their use very risky for eukaryotic cells.

KEY FINDINGS AND CONCLUSIONS

Multiple nanoparticle-based approaches to counter bacterial infections, providing crucial insight into the design of elements that play critical roles in the creation of antimicrobial nanotherapeutic drugs, are currently underway. In this context, plant-based nanoparticles will be less toxic than many other forms, which constitute promising candidates to avoid widespread damage to the microbiome associated with current practices. This article aims to review the actual knowledge on plant-based nanoparticle products for antibiotic resistance and the possible replacement of antibiotics to treat multidrug-resistant bacterial infections.

Ultrahigh-efficiency antibacterial and adsorption performance induced by copper-substituted polyoxomolybdate-decorated graphene oxide nanocomposites

Given the rise of drug-resistant pathogens and industrial contaminants, the development of efficient and eco-friendly water treatment technologies and materials is highly desirable and urgent. Herein, a multifunctional graphene oxide/chitosan/copper-based polyoxometalate (GO/CS/Cu-POM) nanocomposite (Cu-POM, [Cu(L)₄][Cu(L)₃(H₂O)][Cu(L)(H₂O)][P₂Mo₅O₂₃]·4H₂O, L = pyrazole) was synthesized by the ultrasound-assisted self-assembly strategy. The GO/CS/Cu-POM nanocomposite exhibited potent bactericidal properties against gram-positive/negative bacterial strains Staphylococcus aureus (S. aureus, 99.98%), Escherichia coli (E. coli, 99.99%), and drug-resistant E. coli bacterial strains (kanamycin-resistant E. coli 99.93% and ampicillin-resistant E. coli, 97.94%). Further, the antibacterial performance was strongly dependent on synergistic effect between GO/CS and Cu-POM in GO/CS/Cu-POM. The destruction of bacterial membrane and high levels of oxidative stress induced by GO/CS/Cu-POM played a significant role in the bactericidal process. Furthermore, the GO/CS/Cu-POM nanocomposite also displayed superior performance for removal of methylene blue (MB, 96.86%), gentian violet (GV, 97.77%), basic fuchsin (BF, 96.47%), tetracycline (TC, 78.92%) and norfloxacin (NC, 76.26%). Moreover, the main process of dye removal by GO/CS/Cu-POM was controlled by chemisorption. More importantly, the GO/CS/Cu-POM nanocomposite indicated good biocompatibility to human umbilical vein endothelial cells. Current work provides an effective strategy to design multifunctional POM-based composites for water purification and environmental protection.

Effects and relevant mechanisms of non-antibiotic factors on the horizontal transfer of antibiotic resistance genes in water environments: A review

Antibiotic resistance has created obstacles in the treatment of infectious diseases with antibiotics. The horizontal transfer of antibiotic resistance genes (ARGs) can exacerbate the dissemination of antibiotic resistance in water environments. In addition to antibiotic selective pressure, multiple non-antibiotic factors can affect the horizontal transfer of ARGs. Herein, we seek to comprehensively review the effects and relevant mechanisms of non-antibiotic factors on the horizontal transfer of ARGs in water environments, especially contaminants from human activities and water treatment processes. Four pathways have been identified to accomplish horizontal gene transfer (HGT), i.e., conjugation, transformation, transduction, and vesiduction. Changes in conjugative frequencies by non-antibiotic factors are mainly related to their concentrations, which conform to hormesis. Relevant mechanisms involve the alteration in cell membrane permeability, reactive oxygen species, SOS response, pilus, and mRNA expression of relevant genes. Transformation induced by extracellular DNA may be more vulnerable to non-antibiotic factors than other pathways. Except bacteriophage infection, the effects of non-antibiotic factors on transduction exhibit many similarities with that of conjugation. Given the secretion of membrane vesicles stimulated by non-antibiotic factors, their effects on vesiduction can be inferred. Furthermore, contaminants from human activities at sub-inhibitory or environmentally relevant concentrations usually promote HGT, resulting in further dissemination of antibiotic resistance. The horizontal transfer of ARGs is difficult to be inhibited by individual water treatment processes (e.g., chlorination, UV treatment, and photocatalysis) unless they attain sufficient intensity. Accordingly, the synergistic application containing two or more water treatment processes is recommended. Overall, we believe this review can elucidate the significance for risk assessments of contaminants from human activities and provide insights into the development of environment-friendly and cost-efficient water treatment processes to inhibit the horizontal transfer of ARGs.