Bacteria In Aquatic Environments Research Articles

Polysaccharide preferred minority-dominant community assembly and exoenzyme enrichment in transparent exopolymer particles: Implication for global carbon cycle in water

The ubiquitous transparent exopolymer particles (TEPs) are an important organic carbon pool and an ideal microhabitat for bacteria in aquatic environments. They play a crucial role in the global carbon cycle. Organic matter transformation and carbon turnover in TEPs strongly depend on the assembly of their associated bacterial communities and enzyme activity. However, the mechanisms of bacterial community assembly and their potential effects on the organic carbon cycle in TEPs are still unclear. In this study, we comparatively explored the community assembly of TEP-associated bacteria and bacterioplankton from surface freshwater using metagenomics. It was found that the bacterial community assembly in TEPs followed a minority-dominant rule and was governed by homogeneous selection. Pseudomonadota and Actinomycetota, which are responsible for polysaccharide degradation, serve as taxon-specific biomarkers among the abundant and diverse bacteria in TEPs. The network of TEP-associated bacteria displayed stronger robustness than that of bacterioplankton. Bin 76 (majorly Acinetobacter) was the overwhelmingly dominant taxa in TEPs, whereas there was no clearly dominant taxa in TEP-free water. Exoenzyme analysis showed that 64 out of 71 identified polysaccharide hydrolases were markedly linked with the dominant bin 76 in TEPs, while no such linkage was observed for bacterioplankton. Generally, Acinetobacter, which is capable of utilizing polysaccharides, is preferred to be assembled in TEPs together with high polysaccharide hydrolase activity. This may significantly accelerate the turnover of organic carbon in the giant global TEP pool. These findings are important for a deep understanding of the carbon cycle in water.

Antibacterial protein fraction derived from Streptomyces fradiae against septicemia infection in Labeorohita: Breakthrough in marine drug discovery

The aquaculture sector continues to be an essential source of food, revenue, nutrition, and a means of subsistence for numerous people globally. Intensive aquaculture in a confined region induces environmental stress in farmed fish, which indirectly increases their vulnerability to many diseases. Aeromonas hydrophila, Pseudomonas aeruginosa, and Vibrio harveyi are the causative bacterial pathogens for septicemia, the most prevalent and commonly seen illness. Disease outbreaks result in a rise in mortality or a decrease in the quality of the meat, consequently inflicting substantial economic losses to carp production. In contrast, the continual use of antibiotics for infection management has contributed to the proliferation of drug-resistant bacteria in aquatic environments. In this context, marine actinobacteria are emerging as possible sources of new secondary metabolites to combat the problem. Actinobacteria are undoubtedly the most prolific producers of secondary metabolites, and they comprise several commercially and biotechnologically significant species. In this investigation, marine actinobacteria were isolated and evaluated for their antibacterial effectiveness against septicemia pathogens. Effective strains were identified as Nocardiopsis sp., Streptomyces sp., and Pseudonocardia sp. Candidate strains culture filtrates were treated with acetone to precipitate complete proteins. The antibacterial and anti-quorum sensing properties of the crude protein against A. hydrophila MTCC 1739 and P. aeruginosa MTCC 9425 were also examined using the agar well diffusion method. In addition, in vivo investigations of the low molecular weight fraction on Labeorohita demonstrated the fraction's efficacy in reducing septicemia infection. After the 8th day of bathing, fish were found to have recovered.

Indole-3-acetic acid as a cross-talking molecule in algal-bacterial interactions and a potential driving force in algal bloom formation.

Most signaling molecules are involved in inter-or intra-species communication, and signaling involving cross-kingdom cell-to-cell communication is limited. Howerver, algae and bacteria exchange nutrients and information in a range of interactions in marine environments. Multiple signaling molecules exist between algae and bacteria, including quorum-sensing molecules, nitric oxide, and volatile organic compounds. Recently, indole-3-acetic acid (IAA), an auxin hormone that is a well-studied signaling molecule in terrestrial ecosystems, was found to act as a cue in cross-kingdom communication between algae and bacteria in aquatic environments. To increase understanding of the roles of IAA in the phycosphere, the latest evidence regarding the ecological functions of IAA in cross-kingdom communication between algae and bacteria has been compiled in this review. The pathways of IAA biosynthesis, effects of IAA on algal growth & reproduction, and potential mechanisms at phenotypic and molecular levels are summarized. It is proposed that IAA is an important molecule regulating algal-bacterial interactions and acts as an invisible driving force in the formation of algal blooms.

Illustration on phenotypic and genotypic characteristics of typical multi-antibiotic resistant bacteria in aquatic environments through complete genomes and comparative genomics

Antibiotic-resistant bacteria, especially multi-antibiotic-resistant bacteria (MARBs), greatly threaten environmental safety and human health. However, studies on the phenotypic resistance and complete genotypic characterization of MARB in aquatic environments are lacking. In this study, a multi-resistant superbug (TR3) was screened by the selective pressure of multi-antibiotics from the activated sludge of the aeration tanks of urban wastewater treatment plants (WWTPs) in 5 different regions of China. Based on the 16 S rDNA sequence alignment it was found that the sequence similarity between strain TR3 and Aeromonas was as high as 99.50%. The genome-wide sequence showed that the base content of the chromosome of strain TR3 is 4,521,851 bp. It contains a plasmid with a length of 9182 bp. All antibiotic resistance genes (ARGs) of strain TR3 are located on the chromosome, which means that it has passage stability. There are multiple types of resistance genes in the genome and plasmid of strain TR3, enduing it with resistance to 5 antibiotics (ciprofloxacin, tetracycline, ampicillin, clarithromycin, and kanamycin), accompanied by the strongest resistance to kanamycin (aminoglycosides) and the worst resistance to clarithromycin (quinolones). From the perspective of gene expression, we show the resistance mechanism of strain TR3 to different types of antibiotics. In addition, the potential pathogenicity of strain TR3 is also discussed. Chlorine and ultraviolet (UV) sterilization on strain TR3 showed that UV is ineffective at low intensity, and it is easy to be revived by light. A low concentration of hypochlorous acid is effective for sterilization, but it can cause the release of DNA, becoming a potential source of ARGs discharged from WWTPs to environmental water bodies.

Study on hydrolase mechanism of copper compound nanoparticles and its application in the evaluation of gut bacteria in aquatic environment

Conversing proteinaceous enzyme behavior into nanomaterials is intriguing academically, but the threshold from mimicry to accessing sophisticated biological entities has not yet been crossed. Herein, we disclosed the pan-glycoside hydrolases-like (p-GHs-like) activities of Cu3P and Cu2O nanoparticles and decently confirmed their consistent catalytic mechanism as natural glycoside hydrolase, that is, the precise bond breaking, anomeric carbon configuration and catalytic attack mode. We then introduced p-GHs-like NPs into Escherichia coli to establish a feedback regulatory model for the β-D-glucuronidase (expressed by uidA) that was initially expressed in trace amounts. An upregulation of uidA from 72 to 1000 counts was induced by the p-GHs-like activities via pre-released β-glucuronides derivatives, further contributing to 1–2 orders enhancement of the enzyme production. We unearthed the specific catalytic mechanism to unlock a black box of enzyme-like inorganic feedback on the natural enzyme synthesis process, pushing mimicry leaped to physiological behavior.

The mobile gene cassette carrying tetracycline resistance genes in Aeromonas veronii strain Ah5S-24 isolated from catfish pond sediments shows similarity with a cassette found in other environmental and foodborne bacteria.

Aeromonas veronii is a Gram-negative bacterium ubiquitously found in aquatic environments. It is a foodborne pathogen that causes diarrhea in humans and hemorrhagic septicemia in fish. In the present study, we used whole-genome sequencing (WGS) to evaluate the presence of antimicrobial resistance (AMR) and virulence genes found in A. veronii Ah5S-24 isolated from catfish pond sediments in South-East, United States. We found cphA4, dfrA3, mcr-7.1, valF, bla FOX-7, and bla OXA-12 resistance genes encoded in the chromosome of A. veronii Ah5S-24. We also found the tetracycline tet(E) and tetR genes placed next to the IS5/IS1182 transposase, integrase, and hypothetical proteins that formed as a genetic structure or transposon designated as IS5/IS1182/hp/tet(E)/tetR/hp. BLAST analysis showed that a similar mobile gene cassette (MGC) existed in chromosomes of other bacteria species such as Vibrio parahaemolyticus isolated from retail fish at markets, Aeromonas caviae from human stool and Aeromonas media from a sewage bioreactor. In addition, the IS5/IS1182/hp/tet(E)/tetR/hp cassette was also found in the plasmid of Vibrio alginolyticus isolated from shrimp. As for virulence genes, we found the tap type IV pili (tapA and tapY), polar flagellae (flgA and flgN), lateral flagellae (ifgA and IfgL), and fimbriae (pefC and pefD) genes responsible for motility and adherence. We also found the hemolysin genes (hylII, hylA, and TSH), aerA toxin, biofilm formation, and quorum sensing (LuxS, mshA, and mshQ) genes. However, there were no MGCs encoding virulence genes found in A. veronii AhS5-24. Thus, our findings show that MGCs could play a vital role in the spread of AMR genes between chromosomes and plasmids among bacteria in aquatic environments. Overall, our findings are suggesting that MGCs encoding AMR genes could play a vital role in the spread of resistance acquired from high usage of antimicrobials in aquaculture to animals and humans.

Occurrence and Quantitative Microbial Risk Assessment of Methicillin-Resistant Staphylococcus aureus (MRSA) in a Sub-Catchment of the Yodo River Basin, Japan.

The occurrence of Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA) in a sub-catchment of the Yodo River Basin, a representative water system of a drinking water source in Japan, was investigated. The chromogenic enzyme-substrate medium method was used for the detection of S. aureus and MRSA by the presence or absence of antimicrobials in the medium for viable bacteria in a culture-based setting. The contributions of S. aureus and MRSA from wastewater to the rivers were estimated based on mass flux-based analysis, and quantitative microbial risk assessment (QMRA) was further conducted for S. aureus and MRSA in river environments. The mean abundance of S. aureus and MRSA was 31 and 29 CFU/mL in hospital effluent, 124 and 117 CFU/mL in sewage treatment plant (STP) influent, 16 and 13 CFU/mL in STP effluent, and 8 and 9 CFU/mL in river water, respectively. Contribution of the pollution load derived from the target STP effluent to river water ranged from 2% to 25%. The QMRA showed that to achieve the established health benchmarks, the drinking water treatment process would need to yield 1.7 log10 and 2.9 log10 inactivation in terms of infection risk and disability-adjusted life year (DALY) indexes, respectively. These findings highlight the link between medical environment and the importance of environmental risk management for antimicrobial-resistant bacteria in aquatic environments.

Dissemination of Carbapenemases and MCR-1 Producing Gram-Negative Bacteria in Aquatic Environments in Batna, Algeria.

Antibiotic-resistant-bacteria are being considered as emerging environmental contaminants where the importance of the surrounding environment in their emergence and dissemination has been emphasized. The aim of this study was to screen for the presence and diversity of carbapenem- and colistin-resistant Gram-negative bacteria (GNBs) in different aquatic environments. Water samples were collected in Batna, Algeria. Carbapenem- and colistin-resistant GNBs were selectively isolated and then identified using matrix-assisted laser desorption and ionization time-of-flight mass spectrometry. After phenotypic antibiotic susceptibility testing, the molecular mechanisms of β-lactams and colistin-resistance were investigated by PCR and sequencing. The clonality of mcr-1 positive Escherichia coli was determined by multi-locus sequence typing. We noticed a high level of resistance in both tap water and wastewater. The most commonly found carbapenem-resistance mechanism was the OXA-48 enzyme, but other carbapenemases were also detected. In addition, the mcr-1 gene was detected in 18 E. coli of different sequence types. Our findings highlight the role of aquatic environments in the dissemination of resistant-bacteria, especially considering that water is a connecting medium between different ecological systems and can easily transmit resistant-bacteria and promote horizontal gene transfer. Thus, the development of effective treatment strategies for eliminating antibiotic-resistance is seriously needed.

Microplastics a Novel Substratum for Polyhydroxyalkanoate (PHA)-Producing Bacteria in Aquatic Environments.

Polyhydroxyalkanoates (PHA) being biological polymers have attracted great attention. PHA have similar properties to that of synthetic plastic and are biodegradable. To discourage plastic pollution in the environment alternative solutions to the plastic pollution has to be readily available. High cost in production of PHA limits the production of these polymers at industrial scale. Bacteria are screened for PHA from diverse niches to meet the current requirements of cheap PHA production at industrial level. The microbial biofilm formed on the surface of microplastic could be a potential source in providing bacteria of economic importance. This paper is an attempt to search microplastic niche for potential PHA producers. PHA production variation was observed with different parameters such as type of carbon source, nitrogen source concentration and also time of incubation. Bacillus sp. CM27 showed maximum PHA yield up to 32.1% among other isolates at 48 h with 2% glucose as carbon source. Optimization of media leads to increase in PHA yield (37.69%) of CDW in Bacillus sp. CM27. Amino acid sequence of Bacillus sp.CM27 showed the presence of PhaC box with sequence, G-Y-C-M-G-G having cysteine in the middle of the box. The extracted polymer was confirmed by FTIR spectroscopy.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00284-022-02929-y.

Biogeography and diversity patterns of antibiotic resistome in the sediments of global lakes

Lakes act as one of the reservoirs and dispersal routes of antibiotic resistance genes (ARGs) and pathogenic resistant bacteria in aquatic environments. Previous studies reported the occurrence and distribution of ARGs in lakes worldwide; however, few investigated the biogeography and diversity patterns of antibiotic resistome in the environment. To fill this gap, a large-scale data set of sediment metagenomes was collected from globally distributed lakes and characterized comprehensively using metagenomic assembly-based analysis, aiming to shed light on the biogeography and diversity patterns of ARGs in lake ecosystems from a global perspective. Our analyses showed that abundant and diverse ARGs were found in the global lake sediments, including a set of emerging ARGs such as mcr-type and carbapenem-resistant Enterobacteriaceae related genes. Most of the identified ARGs were generally associated with the commonly used antibiotics, suggesting the role of increasing antibiotic consumptions on the resistome prevalence. Spatially, the composition and diversity of ARGs varied across geographical distances and exhibited a scale-dependent distance-decay relationship. Notably, the composition of ARGs was largely shaped by bacterial community structure, and their diversities were co-governed by stochastic process (∼48%) and deterministic process (∼52%). Findings provide a valuable insight to better understand ecological mechanisms of ARGs in lake ecosystems and have important implication for the prevention and control of resistome risk.

Characteristics, Biodiversity, and Cultivation Strategy of Low Nucleic Acid Content Bacteria.

Low nucleic acid content (LNA) bacteria are ubiquitous and estimated to constitute 20%–90% of the total bacterial community in marine and freshwater environment. LNA bacteria with unique physiological characteristics, including small cell size and small genomes, can pass through 0.45-μm filtration. The researchers came up with different terminologies for low nucleic acid content bacteria based on different research backgrounds, such as: filterable bacteria, oligotrophic bacteria, and low-DNA bacteria. LNA bacteria have an extremely high level of genetic diversity and play an important role in material circulation in oligotrophic environment. However, the majority of LNA bacteria in the environment remain uncultivated. Thus, an important challenge now is to isolate more LNA bacteria from oligotrophic environments and gain insights into their unique metabolic mechanisms and ecological functions. Here, we reviewed LNA bacteria in aquatic environments, focusing on their characteristics, community structure and diversity, functions, and cultivation strategies. Exciting future prospects for LNA bacteria are also discussed.

Evidence of Plastic Degrading Bacteria in Aquatic Environment

Introduction: Water bodies are influential part of vitals and help to keep the balance on the earth, to nourish the growing population, as a financial backbone of development, and to save ecosystem along wildlife. Globally, WWF and collaborators are working on plans to secure aquatic resources and are managed sustainably, that’s why water bodies are secure and beneficial for upcoming generations. Findings: The research on pollution, bioremediation and related fields has found that plastic consists of certain chemicals which leach out and mix up with food, drinks and eatables. The health issues are created because of these chemicals that are being linked to health problems such as obesity, indigestion, fertility and immunity etc. Recently a lot of studies identified the involvement of several microorganisms and their enzymes, which are capable of breakdown the plastic material. The microorganism involved in material degradation specifically plastic is identified and well-studied, they consist on seven bacterial and eight fungal species. Among those seven bacterial species five belong to Gram positive while two are Gram negative. The fungal species are of Aspergillus. The species that gave prominent results were Gram +ve: Staphylococcus, Streptococcus, Micrococcus; Gram –ve: Moraxella, and Pseudomonas; and of fungal: Aspergillus glaucus, A. niger. Conclusion: Most of developing countries are using biodegradable plastic instead of ordinary plastic. It is very easy to destroy, after use, and it can minimize the negative effects of marine pollution and environment. It is just like the practice of using biofuel. It can be overcome by environmental pollution

Prevalence and Serotypes diversity of Salmonella Species in the Nile Perch (Lates niloticus) of the Lake Victoria, Tanzania

A cross-sectional study was conducted to estimate the prevalence, serotypes, antimicrobial resistance and plasmids profiles of Salmonella spp. in Nile perch of Lake Victoria, Tanzania. Salmonella spp. and Escherichia coli in water and fish samples were investigated by the bacteriological methods. Antimicrobial resistance profiles of Salmonella spp. were determined using the minimum inhibitory concentration (MIC) method. A total of 324 samples were analysed including Nile perch, water and swabs from surfaces of facilities used for fish transport. The finding showed the prevalence of Salmonella spp. in fish at fishing ground were 16/60 (26.7%), landing sites and markets were 9/60 (15%) and 18/60 (30%) respectively. A significant difference (p<0.05) was observed between the prevalence of Salmonella spp. in fish from fishing ground and those at landing sites, but not with those from markets (p>0.05). The main serotypes recovered were Salmonella ser. Waycross (41: z4z23 :-) and Salmonella enterica ssp. salamae (42: r :-). Most Salmonella serotypes showed the low resistance profiles against most of antimicrobials, but few isolates were resistant to Nalidixic acid 3/64 (4.7%), ampicillin 5/64 (7.8%), azithromycin 14/64 (21.9%) and sulfamethoxazole 22/64 (34.4%). Plasmids were detected in few Salmonella ser. Waycross compared to none of Salmonella ssp. salamae. Escherichia coli count ranged 0.77 to 2.44 log10 cfu/g in fish and 0.44 to 1.71 log10 cfu/ml in water. Contaminated fish with different Salmonella serovars imply pollution of the lake attributable to waste from point and nonpoint sources that may contain antibiotic residues accounting for resistant bacteria in aquatic environment. Un-hygienic fish handling and poor conditions of markets account for the high prevalence of Salmonella spp. in Nile perch at markets.

A Polysaccharide Biosynthesis Locus in Vibrio parahaemolyticus Important for Biofilm Formation Has Homologs Widely Distributed in Aquatic Bacteria Mainly from Gammaproteobacteria.

ABSTRACTVibrio parahaemolyticus is a seafood-borne pathogen that poses a great threat to public health worldwide. It is found in either a planktonic cell or a biofilm form in the natural environment. The cps locus has been the only extensively studied polysaccharide biosynthesis gene cluster involved in biofilm formation for this bacterium. In this study, we found that an additional polysaccharide biosynthesis locus, scv, is also necessary for biofilm maturation. The scv locus is composed of two operons, and a loss of their expression leads to a defective biofilm phenotype. The transcription of the scv locus is under the control of a sigma 54-dependent response regulator, ScvE. In contrast, the quorum-sensing regulator AphA stimulates the expression of the cps locus and the scvABCD operon found in the scv locus. Bioinformatic analyses demonstrated that scv loci are divergent and widely distributed among 28 genera, including 26 belonging to the Gammaproteobacteria and 2 within the Alphaproteobacteria. We also determined that all scv locus-positive species are water-dwelling. Some strains of Aeromonas, Aliivibrio salmonicida, Pseudomonas anguilliseptica, Vibrio breoganii, and Vibrio scophthalmi probably acquired scv loci through insertion sequences and/or integrase-mediated horizontal gene transfer. Gene duplication and fusion were also detected in some scv homologs. Together, our results suggest that the genome of V. parahaemolyticus harbors two distinct polysaccharide biosynthesis loci, which may play a role in fine-tuning biofilm development, and that scv loci likely evolved by horizontal gene transfer, gene loss, gene duplication, and fragment fusion.IMPORTANCE Polysaccharides are the major component of biofilms, which provide survival advantages for bacteria in aquatic environments. The seafood-borne pathogen V. parahaemolyticus possesses a functionally uncharacterized polysaccharide biosynthesis locus, scv. We demonstrated that the scv locus is important for biofilm maturation and that scv expression is positively regulated by ScvE. Strains from 148 aquatic bacterial species possess scv homolog loci. These bacterial species belong to 28 genera, most of which belong to the Gammaproteobacteria class. The evolution and diversification of scv loci are likely driven by horizontal gene transfer, gene loss, gene duplication, and fragment fusion. Our results provide new insights into the function and evolution of this widespread polysaccharide biosynthesis locus.

Use of ozonation technology to combat viruses and bacteria in aquatic environments: problems and application perspectives for SARS-CoV-2

ABSTRACT COVID-19 is a global health threat with a large number of confirmed cases and deaths worldwide. Person-to-person transmission through respiratory droplets and contact with aerosol-infected surfaces are the main ways in which the virus spreads. However, according to the updated literature, the new coronavirus (SARS-CoV-2) has also been detected in aqueous matrices, with the main route of transmission being feces and masks from patients diagnosed with the disease. Given the emergence of public health and environmental protection from the presence of lethal viruses and bacteria, this review article aims to report the major challenges associated with the application of ozonation in water contaminated with viruses and bacteria, in order to clarify whether these communities can survive or infect after the disinfection process and if it is efficient. Available data suggest that ozonation is able to increase the inactivation effect of microorganisms by about 50% in the logarithmic range, reducing infectivity. In addition, the evidence-based knowledge reported in this article is useful to support water and sanitation safety planning and to protect human health from exposure to cited contaminants through water.

Illustration on Phenotypic and Genotypic Characteristics of Typical Multi-Antibiotic Resistant Bacteria in Aquatic Environments Through Complete Genomes and Comparative Genomics

Illustration on Phenotypic and Genotypic Characteristics of Typical Multi-Antibiotic Resistant Bacteria in Aquatic Environments Through Complete Genomes and Comparative Genomics

Heavy metals and microbiome are negligible drivers than mobile genetic elements in determining particle-attached and free-living resistomes in the Yellow River

Suspended particles in water can shelter both microorganisms and contaminants. However, the emerging pollutants antibiotic resistance genes (ARGs) in free-living (FL) or particle-attached (PA) bacteria in aquatic environments are less explored. In this study, we compared the free-living and particle-attached ARGs during four seasons in the Yellow River using high-throughput quantitative PCR techniques and 16S rRNA gene sequencing. Our results demonstrated that both the free-living water and particles were dominated by tetracycline and beta-lactamase resistance genes. The PA-ARGs had a higher absolute abundance than FL-ARGs in the Yellow River, regardless of the season. Both PA-ARGs and FL-ARGs had the highest absolute abundance and diversity during winter. Mobile genetic elements (MGEs) were the dominant driver for both size-fractionated ARGs. However, the microbiome had less influence on PA-ARG profiles than the FL-ARG profiles, while the effects of the heavy metals on ARGs were negligible. The community assembly of both FL-ARG and PA-ARG can be explained by neutral processes. Several opportunistic pathogens (e.g., Escherichia coli) associated with human health exhibited a higher relative abundance in the particles than during a free-living lifestyle. Parts of these pathogens were potential ARG hosts. As such, it is important to monitor the ARGs and opportunistic pathogens from size-fractionated bacteria and develop targeted strategies to manage ARG dissemination and opportunistic pathogens to ensure public health.

Multi-Drug Resistance Bacteria: A Case Study in Western Peninsular Malaysia Freshwaters

The emergence of antibiotic resistant bacteria in aquatic environment has led to an increase in waterborne health risks to an alarming extent. This study attempts to investigate the population of certain antibiotic resistant strains in Peninsular Malaysia. From the samples of 14 rivers from 7 different states in Peninsular Malaysia, a total of 203 isolates were successfully isolated. These are from rivers in Negeri Sembilan, Melaka, Selangor, Kuala Lumpur, Kedah, Kelantan and Terengganu with 35, 15, 37, 39, 24, 26 and 27 isolates, respectively. The isolates were tested for their susceptibility towards 6 broad spectrum of antibiotics which are gentamicin, ampicillin, rifampicin, chloramphenicol, tetracycline, and ciprofloxacin. A total of 117 isolates were identified to have more than 20% MAR index value with 47 of the isolates possess minimum MAR index value of 50%. Based on MAR index value, 59% of isolates are high risk threats indicating a serious emergence of antibiotic resistant bacteria in the rivers in Peninsular Malaysia. Isolates with MAR index value of more than 50% were selected for 16S rRNA gene sequencing for further identification.Based on 16s rRNA gene sequencing, the isolates are a mixture of pathogenic and commensals bacteria. This also implies that the environment especially rivers can be a reservoir for genetic jugglery

Effect of disinfection agents and quantification of potentially viable Leptospira in fresh water samples using a highly sensitive integrity-qPCR assay.

Leptospirosis is an emerging worldwide zoonotic disease, but the general biology of the causative agents is still poorly understood. Humans are an occasional host. The main risk factors are water-associated exposure during professional or recreational activities or during outbreaks in endemic areas. Detecting the presence of pathogenic bacteria in aquatic environments and their capacity to resist various inactivation processes are research fields that need to be further developed. In addition, the methods used for detecting and enumerating Leptospira still need to be improved. We aimed to describe a new quantitative polymerase chain reaction coupled to propidium monoazide treatment (PMAqPCR) that targets not only total Leptospira but also discriminates pathogenic from non-pathogenic Leptospira while also addressing PCR inhibitors, a frequently encountered problem when studying environmental water. In a second step, the killing efficiency of Leptospira to different treatments was tested and PMAqPCR compared to culture-based enumeration. This provided information about the effects of temperature, as well as ultraviolet and chlorine disinfection, that are both related to water treatment processes, in particular for the production of drinking water, on the persistence of both saprophytic and pathogenic Leptospira. Finally, PMAqPCR was used for the detection of Leptospira in freshwater samples for a proof-of-concept. In conclusion, our method could be used for routine freshwater monitoring and allows better evaluation of the presence of Leptospira, allowing evaluation of the bacterial dynamics in a designated area or assessment of the efficacy of water disinfection processes.

Are microplastic particles a hotspot for the spread and the persistence of antibiotic resistance in aquatic systems?

In the last decade, the study of the origin and fate of plastic debris received great attention, leading to a new and broad awareness of the hazard represented by these particles for the environment and the biota. At the same time, the scientific consideration on the leading role of the environment regarding the spread of antibiotic resistant bacteria (ARB) increased. Both, microplastic particles (MPs) and ARB share pollution sources and, in aquatic systems, MPs could act as a novel ecological niche, favouring the survival of pathogens and ARB. MPs can host a specific microbial biofilm, referred to as plastisphere, phylogenetically different from the surrounding planktonic microbial community and from the biofilm growing on other suspended particles. The plastisphere can influence the overall microbiome of a specific habitat, by introducing and supporting different species and by increasing horizontal gene transfer. In this review we collect and analyse the available studies coupling MPs and antibiotic resistance in water, highlighting knowledge gaps to be filled in order to understand if MPs could effectively act as a carrier of ARB and antibiotic resistance genes, and pose a real threat to human health.