Ubiquitous and persistent Proteobacteria and other Gram-negative bacteria in drinking water

Not the Silver Bullet: Uncovering the Unexpected Limited Impacts of Silver-Containing Showerheads on the Drinking Water Microbiome

The incidence of waterborne disease outbreaks in the United States attributed to drinking water-associated pathogens that can cause infections in the immunocompromised DWPIs (e.g., Legionella pneumophila, nontuberculous mycobacteria (NTM), and Pseudomonas aeruginosa, among others) appears to be increasing. An emerging technology adopted to reduce DWPIs are point-of-use devices, such as showerheads that contain silver, a known antimicrobial material. In this study, we evaluate the effect of silver-containing showerheads on DWPI density and the broader microbiome in shower water under real-use conditions in a full-scale shower system, considering three different silver-modified showerhead designs: (i) silver mesh within the showerhead, (ii) silver-coated copper mesh in the head and hose, and (iii) silver-embedded polymer composite compared to conventional plastic and metal showerheads. We found no significant difference in targeted DWPI transcriptional activity in collected water across silver and nonsilver shower head designs. Yet, the presence of silver and how it was incorporated in the showerhead influenced the metal concentrations, microbial rare taxa, and microbiome functionality. Microbial dynamics were also influenced by the showerhead age (i.e., time after installation). The results of this study provide valuable information for consumers and building managers to consider when choosing a showerhead meant to reduce microorganisms in shower water.

The effects of methylparaben exposure on biofilm tolerance to chlorine disinfection

Parabens are emerging contaminants that have been detected in drinking water. Their presence in DW distribution systems (DWDS) can alter bacterial behaviour, characteristics, and structure, which may compromise DW disinfection. This work provides insights into the impact of methylparaben (MP) on the tolerance to chlorine disinfection and antibiotics from dual-species biofilms formed by Acinetobacter calcoaceticus and Stenotrophomonas maltophilia isolated from DW and grown on high-density polyethylene (HDPE) and polypropylene (PPL). Results showed that dual-species biofilms grown on PPL were more tolerant to chlorine disinfection, expressing a decrease of over 50 % in logarithmic reduction values of culturable cells in relation to non-exposed biofilms. However, bacterial tolerance to antibiotics was not affected by MP presence. Although MP-exposed dual-species biofilms grown on HDPE and PPL were metabolically more active than non-exposed counterparts, HDPE seems to be the material with lower impact on DW risk management and disinfection, if MP is present. Overall, results suggest that MP presence in DW may compromise chlorine disinfection, and consequently affect DW quality and stability, raising potential public health issues.

The effects of polypropylene microplastics on the removal of nitrogen and phosphorus from water by Acorus calamus, Iris tectorum and functional microorganisms

Polypropylene microplastics (PP-MPs), an emerging pollutant, adversely affect the ability of aquatic plants to restore water bodies, thereby compromising the functionality and integrity of wetland ecosystems. This study examines the effects of microplastic stress on the nitrogen and phosphorus removal capacities of Acorus calamus and Iris tectorum, as well as on functional microorganisms within the aquatic system. The findings indicate that under PP-MP stress, the nitrogen and phosphorus absorption capabilities of both plants were diminished. Additionally, there was a significant reduction in the metabolic enzyme activities related to nitrogen and phosphorus in the plants, alongside a notable decrease in leaf nitrogen content. PP-MPs hinder the nutrient uptake of plants, affecting their growth and indirectly reducing their ability to utilize nitrogen and phosphorus. Specifically, in the 10 mg L-1 treatment group, A. calamus and I. tectorum showed reductions in leaf nitrogen content by 23.1% and 31.0%, respectively, and by 14.8% and 27.7% in the 200 mg L-1 treatment group. Furthermore, I. tectorum had higher leaf nitrogen levels than A. calamus. Using fluorescent tagging, the distribution of PP-MPs was traced in the roots, stems, and leaves of the plants, revealing significant growth impairment in both species. This included a considerable decline in photosynthetic pigment synthesis, enhanced oxidative stress responses, and increased lipid peroxidation in cell membranes. PP-MP exposure also significantly reduced the abundance of functional microorganisms involved in denitrification and phosphorus removal at the genus level in aquatic systems. Ecological function predictions revealed a notable decrease in nitrogen cycling functions such as nitrogen respiration and nitrite denitrification among water microorganisms in both treatment groups, with a higher ecological risk potential in the A. calamus treatment group. This study provides new insights into the potential stress mechanisms of PP-MPs on aquatic plants involved in water body remediation and their impacts on wetland ecosystems.

Impact of benzalkonium chloride on anaerobic granules and its long-term effects on reactor performance

This study assessed the inhibitory and performance-degrading effects induced by the cationic surfactant benzalkonium chloride (BAC) on anaerobic granules during the long-term operation of a laboratory-scale expanded granular sludge bed (EGSB) reactor. To address the critical scientific problem of how BAC affects the efficiency of EGSB reactors, this research uniquely evaluated the long-term stress response to BAC by systematically comparing continuous and discontinuous inhibitor exposure scenarios. The novel comparison demonstrated that inhibitor concentration is of minor relevance compared to the biomass-specific cumulative inhibitor load in the reactor. After exceeding a critical biomass-specific cumulative inhibitor load of 6.1-6.5 mg BAC/g VS, continuous and discontinuous exposure to BAC caused comparable significant deterioration in reactor performance, including accumulation of volatile fatty acids (VFA), decreased removal efficiency, reduced methane production, as well as the wash-out, flotation, and disintegration of anaerobic granules. BAC exposures had a more detrimental effect on methanogenesis than on acidogenesis. Moreover, long-term stress by BAC led to an inhibition of protein production, resulting in a decreased protein-to-polysaccharide ratio of extracellular polymeric substances (EPS) that promoted destabilizing effects on the granules. Finally, hydrogenotrophic methanogenesis was triggered. Reactor performance could not be restored due to the severe loss of granular sludge.

Diversity and biogeography of bacterial community in the Ili River network varies locally and regionally

Microorganisms in rivers indeed play a crucial role in nutrient cycling within aquatic ecosystems. Understanding the assembly mechanisms of bacterial communities in river networks is essential for predicting their special composition and functional characteristics in natural rivers. This study employed 16S rRNA gene amplicon sequence variation (ASVs) to scrutinize the bacterial community within the uniquely topographical Ili River network. The bacterial community composition varied across the three tributaries with distinct sources and the mainstream. The confluence of various sources diminished the diversity of the bacterial community and altered the functionality of within mainstream. We suggest that strong dispersal limitation predominantly shaped the community at the regional scale (46.6 %), underscoring the significant contribution of headwater sites to bacterial community composition. Contrary to expectation, the bacterial resources in the mainstream were not enriched by the higher diversity in three tributaries. Instead, confluence disturbance potentially increased the undominated processes (36.7 %) and alter the bacterial community composition at the local scale of the mainstream. The intricate coalescence at the confluence could potentially be an intriguing causative factor. Our research indicates that the composition of bacterial communities within intricate river networks exhibits biogeographic patterns, simultaneously influenced by river confluence and geographical features, necessitating multi-scale analysis.

Characterizing the regional distribution, interaction with microorganisms, and sources of dissolved organic matter for summer rainfall: Insights from spectroscopy, community structure, and back-trajectory analyses

Dissolved organic matter (DOM) in rainfall participates in many biogeochemical cycles in aquatic environments and affects biological activities in water bodies. Revealing the characteristics of rainfall DOM could broaden our understanding of the carbon cycle. Therefore, the distribution characteristics and response mechanisms of DOM to microorganisms were investigated in different regions of Hebei. The results indicated that the water quality of the northern region was worse than that of the middle and southern regions. The two protein like components (C1, C2) and one humic like component (C3) were obtained; at high molecular weight (MW), the fluorescence intensity is high in the northern region (0.03 ± 0.02 R.U.), while at low MW, the fluorescence intensity is highest in the southern region (0.50 ± 0.18 R.U.). Furthermore, C2 is significantly positively correlated with C1 (P < 0.01), while C2 is significantly negatively correlated with C3 (P < 0.05) was observed. The spectral index results indicated that rainfall DOM exhibited low humification and highly autochthonous characteristics. The southern region obtained higher richness and diversity of microbial species than northern region (P < 0.05). The community exhibits significant spatiotemporal differences, and the Acinetobacter, Enterobacter, and Massilia, were dominant genus. Redundancy and network analyses showed that the effects of C1, C2, and nitrate on microorganisms increased with decreasing MW, while low MW exhibited a more complex network between DOM and microorganisms than high MW. Meanwhile, C1, C2 had a large total effect on β-diversity and function through structural equation modeling. The backward trajectory model indicates that the sources of air masses are from the northwest, local area, and sea in the northern, middle, and southern regions, respectively. This study broadened the understanding of the composition of summer rainfall DOM and its interactions with microorganisms during rainfall.

Algicidal activity synchronized with nitrogen removal by actinomycetes: Algicidal mechanism, stress response of algal cells, denitrification performance, and indigenous bacterial community co-occurrence

The harmful algal blooms (HABs) can damage the ecological equilibrium of aquatic ecosystems and threaten human health. The bio-degradation of algal by algicidal bacteria is an environmentally friendly and economical approach to control HABs. This study applied an aerobic denitrification synchronization algicidal strain Streptomyces sp. LJH-12-1 (L1) to control HABs. The cell-free filtrate of the strain L1 showed a great algolytic effect on bloom-forming cyanobacterium, Microcystis aeruginosa (M. aeruginosa). The optimal algicidal property of strain L1 was indirect light-dependent algicidal with an algicidal rate of 85.0%. The functional metabolism, light-trapping, light-transfer efficiency, the content of pigments, and inhibition of photosynthesis of M. aeruginosa decreased after the addition of the supernatant of the strain L1 due to oxidative stress. Moreover, 96.05% nitrate removal rate synchronized with algicidal activity was achieved with the strain L1. The relative abundance of N cycling functional genes significantly increased during the strain L1 effect on M. aeruginosa. The algicidal efficiency of the strain L1 in the raw water was 76.70% with nitrate removal efficiency of 81.4%. Overall, this study provides a novel route to apply bacterial strain with the property of denitrification coupled with algicidal activity in treating micro-polluted water bodies.

Bacterial diversity and resistome analysis of drinking water stored in cisterns from two First Nations communities in Manitoba, Canada

The microbiological content of water is an ongoing concern in First Nations communities in Canada. Many communities lack water treatment plants and continue to be under drinking water advisories. However, lack of access to treatment plants is only a part of the problem as poor water distribution systems also contribute to the failure to provide safe drinking water. Here, we studied the microbial diversity and antibiotic resistome from water stored in cisterns from two First Nations communities in Manitoba, Canada. We found that the cistern water contained a high number of bacteria and showed the presence of diverse antimicrobial resistance genes. Interestingly, the bacterial diversity and antimicrobial resistance genes varied considerably from that of the untreated source water, indicating that the origin of contamination in the cistern water came from within the treatment plant or along the delivery route to the homes. Our study highlights the importance of proper maintenance of the water distribution system in addition to access to water treatment facilities to ensure a supply of safe water to First Nations communities in Canada.IMPORTANCEThe work described addresses a critical issue in First Nations communities in Canada-the microbiological content of water. Many of these communities lack access to water treatment plants and frequently experience drinking water advisories. This study focused on the microbial diversity and antibiotic resistome in water stored in cisterns within two First Nations communities in Manitoba, Canada. These findings reveal that cistern water, a common source of drinking water in these communities, contains a high number of bacteria and a wide range of antimicrobial resistance genes. This highlights a serious health risk as exposure to such water can lead to the spread of drug-resistant infections, posing a threat to the well-being of the residents.

Gut microbiota and its metabolites in non-small cell lung cancer and brain metastasis: from alteration to potential microbial markers and drug targets

Background

The elevated mortality rate associated with non-small-cell lung cancer (NSCLC) is a well-established global concern. Considerable attention has been directed toward exploring the association between gut microbiota and various malignant tumors. We herein investigated the associations between the intestinal microbiome and its metabolites, particularly short-chain fatty acids (SCFAs), in patients with NSCLC at different stages, including early and brain metastasis (BM) stages. The findings aim to offer a fresh perspective on the diagnosis and management of NSCLC.

Methods

Fecal samples were collected from 115 participants, comprising healthy controls (n = 35) and patients with treatment-naive NSCLC at the early stage (ELC, n = 40) and the BM stage (n = 40). Characterization of the intestinal microbiome and fecal SCFA levels was performed using 16S rRNA gene sequencing and gas chromatography.

Results

The microbial diversity in patients with NSCLC was found to be less abundant and uniform, particularly in the BM stage. Significant alterations in the community structure of the gut microbiota were observed in patients with NSCLC, with an increase in pathogens in Fusobacteria and Proteobacteria and a decrease in SCFA-producing bacteria in Firmicutes and Actinobacteria, particularly in the BM stage. Meanwhile, microbial communities displayed intricate associations in patients with NSCLC. A biomarker panel (Faecalibacterium, Bifidobacterium, Butyricicoccus, Klebsiella, Streptococcus, and Blautia) successfully distinguished patients in the ELC and BM stages from healthy controls (area under the curve: 0.884). The overall concentration of fecal SCFAs was significantly lower in patients with BM compared to patients with ELC and healthy controls. Subgroup analysis of acetate and butyrate yielded similar results. Moreover, multiple disrupted pathways in the NSCLC group were identified using the Kyoto Encyclopedia of Genes and Genomes annotation, including lipid metabolism and genetic information processing, specifically in the BM stage.

Conclusion

Compared with healthy controls, distinct host-microbe interactions were evident in different phases of patients with NSCLC. Furthermore, specific forms of the gut microbiome and SCFAs may serve as valuable biomarkers and therapeutic targets in the diagnosis and treatment of NSCLC.

Environmental Cadmium Exposure Perturbs Gut Microbial Dysbiosis in Ducks

Ore extraction, chemical production, and agricultural fertilizers may release significant amounts of heavy metals, which may eventually accumulate widely in the environment and organisms over time, causing global ecological and health problems. As a recognized environmental contaminant, cadmium has been demonstrated to cause osteoporosis and renal injury, but research regarding the effects of cadmium on gut microbiota in ducks remains scarce. Herein, we aimed to characterize the adverse effects of cadmium on gut microbiota in ducks. Results indicated that cadmium exposure dramatically decreased gut microbial alpha diversity and caused significant changes in the main component of gut microbiota. Moreover, we also observed significant changes in the gut microbial composition in ducks exposed to cadmium. A microbial taxonomic investigation showed that Firmicutes, Bacteroidota, and Proteobacteria were the most preponderant phyla in ducks regardless of treatment, but the compositions and abundances of dominant genera were different. Meanwhile, a Metastats analysis indicated that cadmium exposure also caused a distinct increase in the levels of 1 phylum and 22 genera, as well as a significant reduction in the levels of 1 phylum and 36 genera. In summary, this investigation demonstrated that cadmium exposure could disturb gut microbial homeostasis by decreasing microbial diversity and altering microbial composition. Additionally, under the background of the rising environmental pollution caused by heavy metals, this investigation provides a crucial message for the assessment of environmental risks associated with cadmium exposure.

Phthalate acid esters promoted the enrichment of chlorine dioxide-resistant bacteria and their functions related to human diseases in rural polyvinyl chloride distribution pipes

Polyvinyl chloride (PVC) pipes are widely used as drinking water distribution pipes in rural areas of China. However, whether phthalate acid esters (PAEs) released from PVC pipes will affect tap water quality is still unknown. The influence of released PAEs on the water quality was analysed in this study, especially after ClO2 disinfection. The results indicated that ClO2 disinfection could control the growth of total coliforms and heterotrophic bacteria (HPC). However, when the ClO2 residual decreased to below 0.10 mg/L, HPC and opportunistic pathogens, including Mycobacterium avium and Pseudomonas aeruginosa, increased significantly. In addition, after ClO2 disinfection, PAEs concentrations increased from 10.6-22.2 μg/L to 21.2-58.8 μg/L in different sampling cites. Linear discriminant analysis (LDA) effect size (LEfSe) and statistical analysis of metagenomic profiles (Stamp) showed that ClO2 disinfection induced the enrichment of Pseudomonas, Bradyrhizobium, and Mycobacterium and functions related to human diseases, such as pathogenic Escherichia coli infection, shigellosis, Staphylococcus aureus infection, and Vibrio cholerae infection. The released PAEs not only promoted the growth of these ClO2-resistant bacterial genera but also enhanced their functions related to human diseases. Moreover, these PAEs also induced the enrichment of other bacterial genera, such as Blastomonas, Dechloromonas, and Kocuria, and their functions, such as chronic myeloid leukaemia, African trypanosomiasis, leishmaniasis, hepatitis C and human T-cell leukaemia virus 1 infection. The released PAEs enhanced the microbial risk of the drinking water. These results are meaningful for guaranteeing water quality in rural areas of China.

Identification of key degraders for controlling toxicity risks of disguised toxic pollutants with division of labor mechanisms in activated sludge microbiomes: Using nonylphenol ethoxylate as an example

Efficient management of disguised toxic pollutants (DTPs), which can undergo microbial degradation and convert into more toxic substances, necessitates the collaboration of diverse microbial populations in wastewater treatment plants. However, the identification of key bacterial degraders capable of controlling the toxicity risks of DTPs through division of labor mechanisms in activated sludge microbiomes has received limited attention. In this study, we investigated the key degraders capable of controlling the risk of estrogenicity associated with nonylphenol ethoxylate (NPEO), a representative DTP, in textile activated sludge microbiomes. The results of our batch experiments revealed that the transformation of NPEO into NP and subsequent NP degradation were the rate-limiting processes for controlling the risk of estrogenicity, resulting in an inverted V-shaped curve of estrogenicity in water samples during the biodegradation of NPEO by textile activated sludge. By utilizing enrichment sludge microbiomes treated with NPEO or NP as the sole carbon and energy source, a total of 15 bacterial degraders, including Sphingbium, Pseudomonas, Dokdonella, Comamonas, and Hyphomicrobium, were identified as capable of participating in these processes, Among them, Sphingobium and Pseudomonas were the two key degraders that could cooperatively interact in the degradation of NPEO with division of labor mechanisms. Co-culturing Sphingobium and Pseudomonas isolates exhibited a synergistic effect in degrading NPEO and reducing estrogenicity. Our study underscores the potential of the identified functional bacteria for controlling estrogenicity associated with NPEO and provides a methodological framework for identifying key cooperators engaged in labor division, contributing to the management of risks associated with DTPs by leveraging intrinsic microbial metabolic interactions.

Surface-modified activated carbon for N-nitrosodimethylamine removal in the continuous flow biological activated carbon columns

The carcinogenic nitrogenous disinfection by-product, N-nitrosodimethylamine (NDMA), is challenging to adsorb due to its high polarity and solubility. Our previous research demonstrated that the adsorptive removal of NDMA can be improved using surface-modified activated carbon (AC800). The current study evaluated the efficacy of AC800 in removing NDMA in a continuous-flow column over 75 days, using both granular activated carbon (GAC) and biologically activated carbon (BAC) columns. The AC800 GAC column demonstrated extended breakthrough and exhaustion times of 10 days and 22 days, respectively, compared to the conventional GAC column at 4 days and 10.5 days. The surface modification effect persisted for 25 days before the removal trends became indistinguishable. The AC800 BAC column outperformed the conventional BAC column with a longer breakthrough time of 11.3 days compared to 7.4 days. BAC columns consistently showed greater NDMA removal, emphasizing the role of biodegradation in NDMA removal on carbon. The higher NDMA removal in the inoculated columns was attributed to increased microbial diversity and the dominance of six specific genera, Methylobacterium, Phyllobacterium, Curvibacter, Acidovorax, Variovorax, and Rhodoferax. This study provides new insights into using modified activated carbon as GAC and BAC media in a real-world continuous-flow setup.

The Treatment of Aquaculture Wastewater with Biological Aerated Filters: From the Treatment Process to the Microbial Mechanism

Algal cell proliferation has posed significant problems for traditional water treatment facilities; these problems are attributed to surface hydrophilicity and electrostatic repulsion. Biological aerated filters (BAFs) have been extensively used in wastewater treatment to remove pollutants such as algal cells by utilizing the adsorption and separation capabilities of the filter media. In this study, a BAF was supplemented with biological filter medium (Marchantia polymorpha) to assess its effectiveness of pretreating aquaculture wastewater. In terms of process performance, steady and consistent treatment was achieved by the BAF with M. polymorpha (BAF2) under an algal cell density as high as 1.65 × 10⁸ cell/L, with average removal rates for NH₄⁺-N and algae cells of 74.4% and 81.9%, respectively. The photosynthetic activity parameters (rETRmax, α, Fv/Fm, and I_k) of the influent and effluent were quantitatively assessed, and M. polymorpha was found to remove algae by disrupting the photosynthetic system of the algal cells. Furthermore, the addition of the M. polymorpha filter medium enhanced the community structure of the functional microbes in the BAF system. The highest microbial community richness and diversity were observed in the BAF2. Meanwhile, M. polymorpha promoted an increase in the abundance of denitrifying bacteria, including Bdellovibrio and Pseudomonas. Overall, this work offers a unique perspective on the aquaculture wastewater pretreatment process and BAF design.

Evaluation of a novel porous antimicrobial media for industrial and HVAC water biocontrol

A novel treatment method, consisting of pea-gravel with a marine coating supplemented with alkyldimethylbenzylammonium chloride (ADBAC or benzalkonium chloride), has been examined for its antimicrobial performance and coating stability in aqueous environments. Initial column studies examining the porous media's ability to reduce bacterial loads in heating, ventilation, and air conditioning (HVAC) water found average reductions of 94% from pre-flush levels (10⁶ colony forming unit (CFU)/mL) when assessed with R2A spread plates and 83% reductions with SimPlates. There was no observed statistical difference between the average of pre- and post-flush waters from four tests of the media without ADBAC. Taxonomic identification, by 16S rRNA gene sequencing, of colonies drawn from pre- and post-ABDAC R2A plates showed similarities with taxa observed in high frequency from prior cultivation-independent surveys of other cooling tower systems. With this proof of concept, two versions of the media were evaluated for potential coating components released during aqueous exposure. Neither released measurable volatile organic compounds (VOC) components, but one did release bisphenol A and ABDAC compounds. Subsequent column tests of the more durable coating were conducted using cultures of interest in industrial water and demonstrated significant reductions in neutralized post-column Enterococcus faecalis samples and near complete loss of Legionella pneumophila in non-neutralized fluids, but lower reductions in Pseudomonas aeruginosa.

Antibiotic resistome alteration along a full-scale drinking water supply system deciphered by metagenome assembly: Regulated by seasonality, mobile gene elements and antibiotic resistant gene hosts

Both drinking water treatment processes and distribution can lead to antibiotic resistome variation, yet the variation of antibiotic resistome in the whole drinking water supply system (DWSS) combined with seasonality remains unknown. In this study, microbial community, antibiotic resistome, mobile genetic elements (MGEs) co-existing with antibiotic resistance genes (ARGs) and ARG hosts would be explored along a DWSS for four seasons with metagenome assembly. Multidrug and bacitracin ARGs were dominant ARGs in DWSS. Integrase, plasmids, recombinase and transposase were major MGEs co-existing with ARGs. Filtration and disinfection treatments could alter the ARG relative abundance, mainly via changing the abundance of ARG hosts (Limnohabitans and Polynucleobacter), which was influenced by water total organic carbon (TOC) content. When TOC was relatively high, filtration could proliferate ARGs via promoting antibiotic resistance bacteria (ARB) but chlorine dioxide could decrease ARGs via killing ARB. Filtration played an important role in controlling ARGs by reducing ARB when TOC was relatively low. The stimulation effect of disinfection on ARGs existed in more oligotrophic environment. Distribution could enrich ARGs in higher temperature by increasing MGEs co-occurring with ARGs and diversifying ARG hosts. MGEs co-occurring with ARGs became more abundant and diverse in disinfected water in warmer seasons. Microbial community was the most important factor determining the antibiotic resistome along a DWSS. These findings extend the knowledge about how and why water treatment processes and pipe distribution shape drinking water antibiotic resistome in different seasons.

Deterministic Processes Shape Abundant and Rare Bacterial Communities in Drinking Water

The deep mechanisms shaping bacterial assembly are a crucial challenge in drinking water ecosystem. However, much less is known about seasonal diversity distributions and assembly mechanisms of abundant and rare bacteria in drinking water. The combination of environmental variables and high-throughput 16S rRNA gene sequencing was conducted to examine the composition, assembly, co-occurrence patterns of abundant and rare bacteria from five drinking water sites across four seasons in one year in China. The results indicated that abundant taxa were mainly composed of Rhizobiales_UG1, Sphingomonadales_UG1, and Comamonadaceae, while rare taxa were Sphingomonadales_UG1, Rhizobiales_UG2, and Rhizobiales_UG1. The richness of rare bacteria was greater than that of abundant ones, and the richness had no differences among seasons. The beta diversity was significantly discrepant in abundant and rare communities and among seasons. Deterministic mechanism accounted for a larger contribution to abundant taxa than rare taxa. Furthermore, water temperature had higher effects on abundant microbiome than rare ones. Co-occurrence network analysis indicated that abundant taxa that occupied frequently in central positions had stronger effect on co-occurrence network. In our study, these results collectively suggested that rare bacteria respond to environmental variables with an analogical pattern to abundant counterparts (similar community assembly), but their ecological diversities, driving forces, and co-occurrence patterns were not equivalent in drinking water.

Characterizing Biofilm Interactions between Ralstonia insidiosa and Chryseobacterium gleum

Ralstonia insidiosa and Chryseobacterium gleum are bacterial species commonly found in potable water systems, and these two species contribute to the robustness of biofilm formation in a model six-species community from the International Space Station (ISS) potable water system. Here, we set about characterizing the interaction between these two ISS-derived strains and examining the extent to which this interaction extends to other strains and species in these two genera. The enhanced biofilm formation between the ISS strains of R. insidiosa and C. gleum is robust to starting inoculum and temperature and occurs in some but not all tested growth media, and evidence does not support a soluble mediator or coaggregation mechanism. These findings shed light on the ISS R. insidiosa and C. gleum interaction, though such enhancement is not common between these species based on our examination of other R. insidiosa and C. gleum strains, as well as other species of Ralstonia and Chryseobacterium. Thus, while the findings presented here increase our understanding of the ISS potable water model system, not all our findings are broadly extrapolatable to strains found outside of the ISS. IMPORTANCE Biofilms present in drinking water systems and terminal fixtures are important for human health, pipe corrosion, and water taste. Here, we examine the enhanced biofilm of cocultures for two very common bacteria from potable water systems: Ralstonia insidiosa and Chryseobacterium gleum. While strains originally isolated on the International Space Station show enhanced dual-species biofilm formation, terrestrial strains do not show the same interaction properties. This study contributes to our understanding of these two species in both dual-culture and monoculture biofilm formation.

Pseudomonadota in the oral cavity: a glimpse into the environment-human nexus

The phylum Pseudomonadota is amongst the most represented in the environment, with a comparatively lower prevalence in the human oral cavity. The ubiquity of Pseudomonadota and the fact that the oral cavity is the most likely entry portal of bacteria from external sources underlie the need to better understand its occurrence in the interface environment-humans. Yet, the relevance oral Pseudomonadota is largely underexplored in the scientific literature, a gap that this review aims at addressing by making, for the first time, an overview of the diversity and ecology of Pseudomonadota in the oral cavity. The screening of scientific literature and human microbiome databases unveiled 1328 reports of Pseudomonadota in the oral cavity. Most of these belonged to the classes Beta- and Gammaproteobacteria, mainly to the families Neisseriaceae, Campylobacteriaceae, and Pasteurelaceae. Others also regularly reported include genera such as Enterobacter, Klebsiella, Acinetobacter, Escherichia, Burkholderia, or Citrobacter, whose members have high potential to acquire virulence and antibiotic resistance genes. This review provides evidence that clinically relevant environmental Pseudomonadota may colonize humans via oral cavity. The need for further investigation about Pseudomonadota at the environment-oral cavity interface and their role as vectors potentially involved in virulence and antibiotic resistance transmission is demonstrated. KEY POINTS: • Neisseriaceae, Campylobacteriaceae, and Pasteurelaceae are part of the core oral microbiome • Enterobacteriaceae, Acinetobacter, or Burkholderia are frequent in the oral microbiome • Gut dysbiosis may be associated with colonization by ubiquitous oral Pseudomonadota.

Evaluation of cadmium tolerance and remediated efficacy of wild and mutated Enterobacter species isolated from potassium nitrate (KNO₃) processing unit contaminated soil

The purpose of this study was to find the most cadmium (Cd²⁺) tolerant and remediated bacteria isolate from KNO₃ processing unit contaminated soil. One isolate out of 19 isolates possessed excellent Cd²⁺ tolerance than others, which was recognized as Enterobacter hormaechei SFC3 through molecular characterization (16S rRNA sequencing). The identified E. hormaechei SFC3 contained 55% and 45% of GC and AT content, respectively. The wild and acridine orange mutated E. hormaechei SFC3 exhibited excellent resistance to Cd²⁺ up to the concentration of 1500 μg mL^-1. Furthermore, the wild E. hormaechei SFC3 and mutated E. hormaechei SFC3 showed 82.47% and 90.21% of Cd²⁺ remediation on 6th days of treatment respectively. Similarly, the Cd²⁺ tolerant wild and mutated E. hormaechei SFC3 showed considerable resistance to all the tested antibiotics. The findings indicate that E. hormaechei SFC3 isolated from KNO₃ processing unit contaminated soil is a promising candidate for microbial remediation of Cd²⁺ contamination.

The Phenomenon of Antibiotic Resistance in the Polar Regions: An Overview of the Global Problem

The increasing prevalence of antibiotic resistance is a global problem in human and animal health. This leads to a reduction in the therapeutic effectiveness of the measures used so far and to the limitation of treatment options, which may pose a threat to human health and life. The problem of phenomenon of antibiotic resistance affects more and more the polar regions. This is due to the increase in tourist traffic and the number of people staying at research stations, unmodernised sewage systems in inhabited areas, as well as the migration of animals or the movement of microplastics, which may contain resistant bacteria. Research shows that the presence of antibiotic resistance genes is more dominant in zones of human and wildlife influence than in remote areas. In a polluted environment, there is evidence of a direct correlation between human activity and the spread and survival of antibiotic-resistant bacteria. Attention should be paid to the presence of resistance to synthetic and semi-synthetic antibiotics in the polar regions, which is likely to be correlated with human presence and activity, and possible steps to be taken. We need to understand many more aspects of this, such as bacterial epigenetics and environmental stress, in order to develop effective strategies for minimizing the spread of antibiotic resistance genes. Studying the diversity and abundance of antibiotic resistance genes in regions with less anthropogenic activity could provide insight into the diversity of primary genes and explain the historical evolution of antibiotic resistance.

Antibiotic resistance genes in Chishui River, a tributary of the Yangtze River, China: Occurrence, seasonal variation and its relationships with antibiotics, heavy metals and microbial communities

The large-scale use and release of antibiotics may create selective pressure on antibiotic resistance genes (ARGs), causing potential harm to human health. River ecosystems have long been considered repositories of antibiotics and ARGs. Therefore, the distribution characteristics and seasonal variation in antibiotics and ARGs in the surface water of the main stream and tributaries of the Chishui River were studied. The concentrations of antibiotics in the dry season and rainy season were 54.18-425.74 ng/L and 66.57-256.40 ng/L, respectively, gradually decreasing along the river direction. The results of antibiotics in the dry season and rainy season showed that livestock and poultry breeding were the main sources in the surface water of the Chishui River basin. Risk assessments indicated high risk levels of OFL in both seasons. In addition, analysis of ARGs and microbial community diversity showed that sul1 and sul3 were the main ARGs in the two seasons. The highest abundance of ARGs was 7.70 × 10⁷ copies/L, and intl1 was significantly positively correlated with all resistance genes (p< 0.01), indicating that it can significantly promote the transmission of ARGs. Proteobacteria were the dominant microorganisms in surface water, with a higher average abundance in the dry season (60.64 %) than in the rainy season (39.53 %). Finally, correlation analyses were performed between ARGs and antibiotics, microbial communities and heavy metals. The results showed that there was a significant positive correlation between ARGs and most microorganisms and heavy metals (p< 0.01), indicating that occurrence and transmission in the environment are influenced by various environmental factors and cross-selection. In conclusion, the persistent residue and transmission of ARGs and their transfer to pathogens are a great threat to human health and deserve further study and attention.

Microbial Community Structure and Diversity in Drinking Water Supply, Distribution Systems as well as Household Point of Use Sites in Addis Ababa City, Ethiopia

Understanding ecology of microbiomes in drinking water distribution systems is the most important notion in delivering safe drinking water. Drinking water distribution systems harbor various microbiota despite efforts made in improving water infrastructures in the water industry, especially, in developing countries. Intermittent water supply, long time of water storage, low water pressure, and contaminated source water are among many of the factors responsible for poor drinking water quality affecting health of people. The aim of this study was to explore microbial diversity and structure in water samples collected from source water, treated water, reservoirs, and household points of use locations (taps). High-throughput Illumina sequencing technology was employed by targeting the V4 region of the 16S rRNA gene and the V1-V3 region of the 18S rRNA gene to analyze the microbial community structure. Proteobacteria followed by Firmicutes, Bacteroidetes, and Actinobacteria were the core dominating taxa. Gammaproteobacteria was also dominant among other proteobacterial classes across all sampling points. Opportunistic bacterial genera such as Pseudomonas, Legionella, Klebsiella, Escherichia, and Actinobacteria, as well as eukaryotic microbes like Cryptosporidium, Hartmannella, Acanthamoeba, Aspergillus, and Candida were also abundant taxa found along the distribution systems. The shift in microbial community structure from source to point of use locations was influenced by basic factors such as residual chlorine, intermittent water supply, and long-time storage at the household. The complex microbiota detected in different sampling sites in this study brings drinking water quality problem which further causes significant health problems to both human and animal health. Treatment ineffectiveness, disinfection inefficiency, poor maintenance actions, leakage of sewage, and other domestic wastes are few among many other factors responsible for degraded drinking water quality in this study putting health at high risk. Findings of this research provide important and baseline information to understand the microbial profiles of drinking water along source water and distribution systems. Moreover, knowing the microbial profile will help to design proper water quality assurance approaches.

Rice washing drainage (RWD) embedded in poly(vinyl alcohol)/sodium alginate as denitrification inoculum for high nitrate removal rate with low biodiversity

Immobilization technology with low maintenance is a promising alternative to enhance nitrate removal from water. In this study, washing rice drainage (RWD) was immobilized by poly(vinyl alcohol)/sodium alginate (PVA/SA) to obtain RWD-PVA/SA gel beads as inoculum for denitrification. When initial nitrate concentration was 50 mg N/L, nitrate was effectively removed at rates of 50-600 mg/(L∙d) using acetate as carbon source (C/N = 1.25). Arrhenius activation energy (Ea) of nitrate oxidoreductase was 28.64 kJ/mol for the RWD-PVA/SA gel beads. Temporal and spatial variation in microbial community structures were revealed along with RWD storage and in the reactors by Illumina high-throughput sequencing technology. RWD-PVA/SA gel beads has a simple (operational taxonomic units (OTUs) 〈100). Dechloromonas, Pseudomonas, Flavobacterium and Acidovorax were the most four dominant genera in the denitrification reactors inoculated with RWD-PVA/SA gel beads. This study provides an inoculum for denitrification with high nitrate removal performance and simple microbial community structures.

Crosstalk Between the Gut and Brain: Importance of the Fecal Microbiota in Patient With Brain Tumors

Background

Variations in the gut microbiota may affect the metabolism, inflammation and immune response of the host. Microbiota dysbiosis has been extensively investigated in neurological disorders and diseases of the central nervous system (CNS). However, the alterations of the gut microbiota in patients suffering from brain tumors and the associations of the gut microbiota with these diseases remain unknown. Herein, we investigate the alterations of the gut microbiota community in patients with brain tumors and the associations between the two and further explore microbial markers used for the diagnosis of brain tumors.

Methods

In our study, we recruited 158 participants, consisting of 101 brain tumor patients (65 benign and 36 malignant cases) and 57 age- and sex-matched healthy controls (HCs). We characterized the gut microbial community by using 16S rRNA gene amplicon sequencing and investigated its correlations with clinical features.

Results

The results showed remarkably less microbial ecosystem richness and evenness in patients with brain tumors than in HCs. The gut microbiota community structure underwent profound changes in the brain tumor group, including an increase in the abundances of pathogenic bacteria, such as Fusobacteriota and Proteobacteria and a reduction in the abundances of probiotic bacteria, such as Bifidobacterium or Lachnospira. Moreover, our study indicated more significant correlations and clustering of pathogens in the malignant brain tumor group. Furthermore, a biomarker panel was used to discriminate the brain tumor patients from the healthy controls (AUC: 0.77). Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation revealed an accumulation of harmful metabolites and disorders of the basic physiological pathways in the brain tumor group.

Conclusions

Our study revealed that brain tumor patients may possess divergent host-microbe interactions from those of healthy controls, especially in malignant brain tumor patients. In addition, the intestinal flora may be involved in immune responses and metabolism in the microenvironment of brain tumors. All evidence, including the biomarker panel, suggests that the intestinal flora may be a useful diagnostic and predictive tool and an important preventive target for brain tumors.

Drinking Water Supplemented with Acidifiers Improves the Growth Performance of Weaned Pigs and Potentially Regulates Antioxidant Capacity, Immunity, and Gastrointestinal Microbiota Diversity

This study evaluated the potential effects of adding acidifiers to the drinking water on the growth performance, complete blood count, antioxidant indicators, and diversity of gastrointestinal microbiota for weaned pigs. A total of 400 weaned pigs were randomly divided into four treatments. Pigs were fed the same basal diet and given either water (no acidifier was added, control) or water plus blends of different formulas of acidifiers (acidifier A1, A2, or A3) for 35 days. On d 18 and 35 of the experimental period, 64 pigs (four pigs per pen) were randomly selected to collect blood for a CBC test (n = 128) and an antioxidant indicators test (n = 128); 24 pigs (six pigs per group) were randomly selected to collect fresh feces (n = 48) from the rectum for 16S rRNA gene sequencing. Compared to the control, supplementing the drinking water with acidifiers improved the growth performance and survival rate of weaned pigs. Acidifier groups also increased serum catalase (CAT) and total antioxidant capacity (T-AOC) activities, while also displaying a decreased malondialdehyde (MDA) concentration compared to the control. The relative abundance of Firmicutes in the acidifier A1 group was greater than that in the control group (p < 0.05) on d 35; the relative abundance of Lactobacillus in the acidifier A1 group was greater than that in the control group (p < 0.05) on d 18 and 35. The microbial species Subdoligranulum or Ruminococcaceae_UCG-005 had significantly positive correlations with ADG and ADFI or with serum antioxidant indicators, respectively. These findings suggest that supplementing the drinking water with an acidifier has a potential as an antioxidant, which was reflected in the improvement of growth performance, immunity, antioxidant capacity, and intestinal flora.

Variation in the Structure and Composition of Bacterial Communities within Drinking Water Fountains in Melbourne, Australia

Modern drinking water distributions systems (DWDSs) have been designed to transport treated or untreated water safely to the consumer. DWDSs are complex environments where microorganisms are able to create their own niches within water, biofilm or sediment. This study was conducted on twelve drinking fountains (of three different types, namely types A, B and C) within the Melbourne (Australia) city area with the aim to (i) characterize the water quality and viable and total counts at each fountain, (ii) compare the differences in the structure and diversity of the bacterial community between bulk water and biofilm and (iii) determine differences between the bacterial communities based on fountain type. Samples of water and biofilm were assessed using both culture-dependent and culture-independent techniques. Heterotrophic plate counts of water samples ranged from 0.5 to 107.5 CFU mL−1, and as expected, total cell counts (cells mL−1) were, on average, 2.9 orders of magnitude higher. Based on the mean relative abundance of operational taxonomic units (OTUs), ANOSIM showed that the structure of the bacterial communities in drinking water and biofilm varied significantly (R = 0.58, p = 0.001). Additionally, ANOSIM showed that across fountain types (in water), the bacterial community was more diverse in fountain type C compared to type A (p < 0.001) and type B (p < 0.001). 16S rRNA next-generation sequencing revealed that the bacterial communities in both water and biofilm were dominated by only seven phyla, with Proteobacteria accounting for 71.3% of reads in water and 68.9% in biofilm. The next most abundant phylum was Actinobacteria (10.4% water; 11.7% biofilm). In water, the genus with the highest overall mean relative abundance was Sphingomonas (24.2%), while Methylobacterium had the highest mean relative abundance in biofilm samples (54.7%). At the level of genus and higher, significant differences in dominance were found across fountain types. In water, Solirubrobacterales (order) were present in type C fountains at a relative abundance of 17%, while the mean relative abundance of Sphingomonas sp. in type C fountains was less than half that in types A (25%) and B (43%). In biofilm, the relative abundance of Sphingomonas sp. was more than double in type A (10%) fountains compared to types B (4%) and C (5%), and Sandarakinorhabdus sp. were high in type A fountains (6%) and low in types B and C (1%). Overall this research showed that there were significant differences in the composition of bacterial communities in water and biofilm from the same site. Furthermore, significant variation exists between microbial communities present in the fountain types, which may be related to age. Long-established environments may lead to a greater chance of certain bacteria gaining abilities such as increased disinfection resistance. Variations between the structure of the bacterial community residing in water and biofilm and differences between fountain types show that it is essential to regularly test samples from individual locations to determine microbial quality.

Effects of treatment processes on AOC removal and changes of bacterial diversity in a water treatment plant

The effectiveness of different treatment processes on assimilable organic carbon (AOC) removal and bacterial diversity variations was evaluated in a water treatment plant. The van der Kooij technique was applied for AOC analysis and responses of bacterial communities were characterized by the metagenomics assay. Results show that the AOC concentrations were about 93, 148, 43, 51, 37, and 38 μg acetate-C/L in effluents of raw water basin, preozonation, rapid sand filtration (RSF), ozonation, biofiltration [biological activated carbon (BAC) filtration], and chlorination (clear water), respectively. Increased AOC concentrations were observed after preozonation, ozonation, and chlorination units due to the production of biodegradable organic matters after the oxidation processes. Results indicate that the oxidation processes were the main causes of AOC formation, which resulted in significant increases in AOC concentrations (18-59% increment). The AOC removal efficiencies were 47, 28, and 60% in the RSF, biofiltration, and the whole system, respectively. RSF and biofiltration were responsible for the AOC treatment and both processes played key roles in AOC removal. Thus, both RSF and biofiltration processes would contribute to AOC treatment after oxidation. Sediments from the raw water basin and filter samples from RSF and BAC units were collected and analyzed for bacterial communities. Results from scanning electron microscope analysis indicate that bacterial colonization was observed in filter materials. This indicates that the surfaces of the filter materials were beneficial to bacterial growth and AOC removal via the adsorption and biodegradation mechanisms. Next generation sequencing analyses demonstrate that water treatment processes resulted in the changes of bacterial diversity and community profiles in filters of RSF and BAC. According to the findings of bacterial composition and interactions, the dominant bacterial phyla were Proteobacteria (41% in RSF and 56% in BAC) followed by Planctomycetes and Acidobacteria in RSF and BAC systems, which might affect the AOC biodegradation efficiency. Results would be useful in developing AOC treatment and management processes in water treatment plants.

Characteristics of antibiotic resistance genes in full-scale anaerobic digesters of food waste and the effects of application of biogas slurry on soil antibiotic resistance genes

The fate of antibiotic resistance genes (ARGs) in full-scale anaerobic digestion (AD) of food waste (FW) and in the soil applied with biogas slurry has not been fully understood. In this study, 12 targeted ARGs and intI1 in FW, intermediate product, and biogas slurry from three full-scale AD were analyzed. The results showed that subcritical water pretreatment was an effective method for ARG attenuation, by which the absolute abundance of total targeted ARGs was removed by 99.69%. The predominant ARGs (ermB, tetM, and tetW) in FW were removed more than 99% after subcritical water pretreatment. The result of field experiments with biogas slurry as fertilizer showed that the absolute abundance of several ARGs (sul2, tetM, blaOXA-1, blaTEM) and intI1 accumulated significantly compared to the control group (CK) during three consecutive growth stages of the rice. The detected abundance of ARGs in paddy field soil increased from 190.50 (CK) to 8.87 × 10⁴ copies/g (wet weight) (soil) during tillering stage, and increased from 4102.65 (CK) to 4.38 × 10⁴ copies/g (wet weight) (soil) during heading time. Biogas slurry improved the soil nutrients (TN, AN, TP, and AP); meanwhile, the concentrations of total salt and Cl^- increased. Network analysis indicated that 28 genera were the possible hosts of ARGs; variation partitioning analysis (VPA) indicated that microbial communities (contribution 59.30%) were the main factors that affected the fate of ARGs and intI1.

Dynamics of antibiotics and antibiotic resistance genes in four types of kitchen waste composting processes

Kitchen waste might be a potential source of antibiotics and antibiotic resistance genes. Composting is recognized as an effective way for kitchen waste disposal. However, the effects of different kitchen waste composting types on the removal of antibiotics and antibiotic resistance genes haven't been systematically studied. In this study, the dynamics of antibiotics and antibiotic resistance genes from kitchen waste of four composting processes were compared. Results showed that although kitchen waste was composted, it remained an underestimated source of antibiotics (25.9-207.3 μg/kg dry weight) and antibiotic resistance genes (10¹²-10¹⁷ copies/kg dry weight). Dynamic composting processes (i.e., dynamic pile composting and mechanical composting) decreased the antibiotic removal efficiency and increased the abundance of some antibiotic resistance genes (5.35-8534.7% enrichment). Partial least-squares path model analysis showed that mobile genetic elements played a dominant role in driving antibiotic resistance genes dynamics. Furthermore, redundancy analysis revealed that temperature, pH, and water content considerably affected the removal of antibiotics and mobile genetic elements. This study provides further insights into exploring the effective strategies in minimizing the risk of antibiotic resistance from kitchen waste via composting process.

Bacteriome composition analysis of selected mineral water occurrences in Serbia

Bacterial metabarcoding analysis by 16S rDNA of five occurrences of mineral waters in Serbia (Torda, Slankamen Banja, Lomnicki Kiseljak, Velika Vrbnica and Obrenovacka Banja) indicated the presence of a high percentage of the Proteobacteria phylum, followed by the Bacteroidetes phylum. The families Rhodobacteraceae, Burkholderiaceae, Pseudomonadaceae, Methylophilaceae and Moraxellaceae were the most dominant in the bacterial flora of the selected occurrences, whereas the most represented genera were Acinetobacter, Pseudorhodobacter, Pseudomonas, Limnohabitans, Massilia, Limnobacter and Methylotenera. The presence of coliform bacteria was not detected. Alpha diversity analysis revealed that Slankamen Banja and Lomnicki Kiseljak were the richest of the selected occurrences, while the mineral waters of Torda, Velika Vrbnica and Obrenovacka Banja were characterized by similar diversity of bacterial communities determined by beta diversity analysis. Physical-chemical analysis revealed the value of total dissolved solids above 1 g/L, as well as elevated concentrations of some metals and non-metals. The research concluded that specific bacteria contribute to the development of biocorrosion and biofouling processes of water intake facilities. In addition, some of these bacteria might be potential indicators of the organic sources of pollution and/or biotechnological natural remediators in the treatment of contaminated waters.

Neonatal calf diarrhea: A potent reservoir of multi-drug resistant bacteria, environmental contamination and public health hazard in Pakistan

Though emergence of multi-drug resistant bacteria in the environment is a demonstrated worldwide phenomenon, limited research is reported about the prevalence of resistant bacteria in fecal ecology of neonatal calf diarrhea (NCD) animals in Pakistan. The present study aimed to identify and assess the prevalence of bacterial pathogens and their resistance potential in the fecal ecology of NCD diseased animals of Pakistan. The presence of antibiotic resistance genes (bla_TEM, bla_NDM-1, bla_CTX-M, qnrS) was also investigated. A total of 51 bacterial isolates were recovered from feces of young diarrheic animals (n = 11), collected from 7 cities of Pakistan and identified on the basis of 16S rRNA gene sequence and phylogenetic analysis. Selected isolates were subjected to antimicrobial susceptibility by disc diffusion method while polymerase chain reaction (PCR) was used to characterize the bla_TEM, bla_NDM-1, bla_CTX-M, qnrS and mcr-1 antibiotic resistance genes. Based on the 16S rRNA gene sequences (Accession numbers: LC488898 to LC488948), all isolates were identified that belonged to seventeen genera with the highest prevalence rate for phylum Proteobacteria and genus Bacillus (23%). Antibiotic susceptibility explained the prevalence of resistance in isolates ciprofloxacin (100%), ampicillin (100%), sulfamethoxazole-trimethoprim (85%), tetracycline (75%), amoxicillin (55%), ofloxacin (50%), ceftazidime (45%), amoxicillin/clavulanic acid (45%), levofloxacin (30%), cefpodoxime (25%), cefotaxime (25%), cefotaxime/clavulanic acid (20%), and imipenem (10%). MICs demonstrated that almost 90% isolates were multi-drug resistant (against at least three antibiotics), specially against ciprofloxacin, and tetracycline with the highest resistance levels for Shigella sp. (NCCP-421) (MIC-CIP up to 75 μg mL^-1) and Escherichia sp. (NCCP-432) (MIC-TET up to 250 μg mL^-1). PCR-assisted detection of antibiotic resistance genes showed that 54% isolates were positive for bla_TEM gene, 7% isolates were positive for bla_CTX-M gene, 23% isolates were positive for each of qnrS and mcr-1 genes, 23% isolates were co-positive in combinations of qnrS and mcr-1 genes and bla_TEM and mcr-1 genes, whereas none of the isolate showed presence of bla_NDM-1 gene.

Optimizing temperature for enhancing waste activated sludge decomposition in lysozyme and rhamnolipid pretreatment system

This study investigated the influence of temperature on the hydrolysis and decomposition of waste activated sludge (WAS) during the enhanced pretreatment system with lysozyme and rhamnolipid (Ly + RL). Results showed that temperature increasing from 15℃ to 55℃ could obviously enhance the release of soluble organic matters and WAS decomposition degree within the Ly + RL pretreatment system. Compared to the sum of sole Ly and sole RL pretreatment, Ly + RL combined pretreatment system at 45℃ presented best synergistic hydrolysis performance. The decomposition degree of bacteria and archaea reached 47.6% and 88.1%, respectively. Meanwhile, increasing temperature could recede the diversity of microbial community in the system. Gammaproteobacteria, with the relative abundance of 90.7%, occupied the absolute dominant position at 45℃. Furthermore, with the rise of temperature, more volatile fatty acids were harvested after anaerobic fermentation.

Disinfection Performance of a Drinking Water Bottle System With a UV Subtype C LED Cap Against Waterborne Pathogens and Heterotrophic Contaminants

The purgaty One systems (cap+bottle) are portable stainless-steel water bottles with UV subtype C (UVC) disinfection capability. This study examines the bottle design, verifies disinfection performance against Escherichia coli, Pseudomonas aeruginosa, Vibrio cholerae, and heterotrophic contaminants, and addresses the public health relevance of heterotrophic bacteria. Bottles were inoculated with deliberately contaminated potable water and disinfection efficacy examined using colony forming unit (CFU) assay for each bacterial strain. The heterotrophic plate count (HPC) method was used to determine the disinfection performance against environmental contaminants at day 0 and after 3days of water in stationary condition without prior UVC exposure. All UVC irradiation experiments were performed under stationary conditions to confirm that the preset application cycle of 55s offers the desired disinfection performance under-tested conditions. To determine effectiveness of purgaty One systems (cap+bottle) in disinfection, inactivation efficacy or log reduction value (LRV) was determined using bacteria concentration between UVC ON condition and controls (UVC OFF). The study utilized the 16S ribosomal RNA (rRNA) gene for characterization of isolates by identifying HPC bacteria to confirm if they belong to groups that are of public health concern. Purgaty One systems fitted with Klaran UVC LEDs achieved 99.99% inactivation (LRV4) efficacy against E. coli and 99.9% inactivation (LRV3) against P. aeruginosa, V. cholerae, and heterotrophic contaminants. Based on the 16S rRNA gene analyses, the study determined that the identified HPC isolates from UVC irradiated water are of rare public health concern. The bottles satisfactorily inactivated the target pathogenic bacteria and HPC contaminants even after 3days of water in stationary condition.

Lotus seed resistant starch affects the conversion of sodium taurocholate by regulating the intestinal microbiota

We investigated the ability of lotus seed resistant starch (LRS) to affect the conversion of sodium taurocholate (STCA) by regulating the intestinal flora, using glucose (GLU) and high amylose corn starch (HAMS) as controls. The dominant microbiota in LRS group were mainly Lactobacillus and Escherichia_Shigella, with a small proportion of Bifidobacterium. Meanwhile, Lactobacillus, Bifidobacterium and Enterococcus were dominant microbiota in the HAMS group. Lactobacillus, Burkholderia-Caballeronia-Paraburkholderia and Sphingomonas were found in the GLU group. Furthermore, Bifidobacterium, Enterococcus and Escherichia_Shigella were negatively correlated with STCA and sodium taurodeoxycholate (STDCA), while these bacteria were positively correlated with bile salt hydrolase (BSH) and hydroxysteroid dehydrogenase (HSDH) content. Meanwhile Burkholderia-Caballeronia-Paraburkholderia and Sphingomonas were positively correlated with STCA and STDCA, while these bacteria were negatively correlated with BSH and HSDH content. LRS promoted the proliferation of Bifidobacterium and Escherichia_Shigella to secret more BSH and HSDH, accelerating the hydrolysis of STCA and reducing the conversion of STDCA.

Irrigating digestate to improve cadmium phytoremediation potential of Pennisetum hybridum

The bioavailability of heavy metal and growth of hyperaccumulator are key factors controlling the phytoextraction of heavy metal from soil. In this study, the efficacy and potential microbial mechanisms of digestate application in enhancing Cd extraction from soil by Pennisetum hybridum were investigated. The results showed that digestate application significantly promoted the height, tiller number, and biomass yield of Pennisetum hybridum. The application also increased the activities of urease, sucrase, dehydrogenase, available Cd contents of rhizosphere soils (from 2.21 to 2.46 mg kg^-1), and the transfer factors of Cd from root to shoot and leaf. Assuming three annual harvests, digestate application would substantially reduce time needed for Pennisetum hybridum to completely absorb Cd from soil-from 15-16 yr-10 yr. Furthermore, the results of microbial community diversity analysis showed that digestate irrigation was more facilitated for the growth of the predominant bacteria, which were Actinobacteria and Chloroflexi at phylum level, and Sphingomonas and Nitrospiraat genus level, which mainly have the functions of promoted plant growth and metal resistance. The results suggested that the enhanced phytoextraction of Cd by Pennisetum hybridum with digestate application might mainly attributed to the increased Cd bio-availability and the enhanced plant growth, indicating that an approach combining digestate and Pennisetum hybridum could be a promising strategy for remediating Cd-contaminated soils.

Decisive Effects of Life Stage on the Gut Microbiota Discrepancy Between Two Wild Populations of Hibernating Asiatic Toads (Bufo gargarizans)

Until now, the effects of driving factors on the gut microbiota of amphibians are still mostly confounded. Due to a long-term fasting, hibernating amphibians are ideal experimental materials to explore this question. In this study, we characterized the small intestine microbiota of adult hibernating Asiatic toads (Bufo gargarizans) collected from two geographical populations using 16S rRNA amplicon sequencing technique and evaluated the effects of non-dietary factors (e.g., sex and host genetic background). Proteobacteria (0.9196 ± 0.0892) was characterized as the most dominant phylum in the small gut microbiota of hibernating Asiatic toads, among which five core OTUs were identified and three were classified into Pseudomonas. In view of the coincidence between the dominant KEGG pathways (such as the two-component system) and Pseudomonas, Pseudomonas appeared to be a key adaptor for small gut microbiota during hibernation. Furthermore, we detected a greater discrepancy of gut microbiota between geographical populations than between sexes. Both sex and host genetic background showed a minor effect on the gut microbiota variation. Finally, life stage was determined to be the decisive factor driving the gut microbiota discrepancy between populations. However, a large proportion of the gut microbiota variation (∼70%) could not be explained by the measured deterministic factors (i.e., sex, location, body length, and routine blood indices). Therefore, other factors and/or stochastic processes may play key roles in shaping gut bacterial community of hibernating amphibians.

Microbial communities of biofilms developed in a chlorinated drinking water distribution system: A field study of antibiotic resistance and biodiversity

Antibiotic resistance and biodiversity were investigated in microbial communities attached to inner surfaces of water supply fittings in a chlorinated drinking water distribution system (DWDS) supplied by two independent water treatment plants (WTPs) drawing the same source water. The investigation of the effect of the season, the applied water treatment technology, and type, material, and age of water supply fittings on both antibiotic resistance and biodiversity in biofilms involved collection of tubercles during summer and winter seasons throughout the DWDS. A total of 16 samples were collected (8 per season) from areas supplied by two independent WTPs. Culturable aerobic antibiotic resistant bacteria (ARB) proved more prevalent in summer. Various antibiotic resistance genes (ARGs) were detected, confirming the role of biofilms as ARGs reservoirs, but the abundances of quantified genes (sulI, ermB, qacEΔ1, intI1) were low (a range of <LOQ to 2313 gene copies/mg dry mass of tubercles) throughout the DWDS. In terms of microbial community composition, Proteobacteria were dominant in each sample (51.51-97.13%), and the most abundant genus was Desulfovibrio (0.01-66.69%) belonging to sulphate-reducing bacteria. Biodiversity of microbial communities was shaped by many coexisting factors, including season, water supply fitting material, and sampling site location. Spatial distribution analysis revealed that although only samples collected at the same sampling sites were similar to each other in terms of antibiotic resistance, some samples collected in the close proximity were similar in terms of biodiversity. This suggests that antibiotic resistance spreads only locally over small distances in drinking water biofilms. Although actual drinking water biofilms have been previously investigated in terms of microbial biodiversity, this is the first study that characterised both antibiotic resistance and biodiversity of microbial communities attached to inner surfaces of a real DWDS functioning for decades.

Distinct Microbial Community of Accumulated Biofilm in Dental Unit Waterlines of Different Specialties

The contamination of dental unit waterlines (DUWLs) is a serious problem and directly affects the dental care. This study aims to explore the microbial community of biofilm in DUWL from different specialties and investigate the associated factors. A total of 36 biofilm samples from 18 DUWL of six specialties (i.e., prosthodontics, orthodontics, pediatrics, endodontics, oral surgery, and periodontics) at two time points (i.e., before and after daily dental practice) were collected with a novel method. Genomic DNA of samples was extracted, and then 16S ribosomal DNA (rDNA) (V3–V4 regions) and ITS2 gene were amplified and sequenced. Kruskal–Wallis and Wilcoxon rank test were adopted for statistical analysis. Microbial community with high diversity of bacteria (631 genera), fungi (193 genera), and viridiplantae was detected in the biofilm samples. Proteobacteria was the dominant bacteria (representing over 65.74–95.98% of the total sequences), and the dominant fungi was Ascomycota (93.9–99.3%). Microorganisms belonging to multiple genera involved in human diseases were detected including 25 genera of bacteria and eight genera of fungi, with relative abundance of six genera over 1% (i.e., Acinetobacter, Pseudomonas, Enterobacter, Aspergillus, Candida, and Penicillium). The biofilm microbiome may be influenced by the characteristics of dental specialty and routine work to some extent. The age of dental chair unit and overall number of patients had the strongest impact on the overall bacteria composition, and the effect of daily dental practices (associated with number of patients and dental specialty) on the fungi composition was the greatest. For the first time, biofilm in DUWL related to dental specialty was comprehensively evaluated, with more abundance of bacterial and fungal communities than in water samples. Biofilm accumulation with daily work and multiple kinds of opportunistic pathogen emphasized the infectious risk with dental care and the importance of biofilm control.

Microbial community in biofilters for water reuse applications: A critical review

The combination of ozonation (O₃) and biofiltration processes has become practical and desirable in advanced water reclamation for water reuse applications. However, the role of microbial community and its characteristics (source, abundance, composition, viability, structure) on treatment performance has not received the same attention in water reclamation biofilters as in other applications, such as in drinking water biofilters. Microbial community characterization of biofilters used in water reuse applications will add evidence to better understand the potential microorganisms, consequent risks, and mechanisms that will populate drinking water sources and ultimately influence public health and the environment. This critical review provides insights into O₃-biofiltration as a treatment barrier with a focus on development, structure, and composition of the microbial community characteristics involved in the process. The effect of microorganism seeding by the influent before and after the biofilter and ozone oxidation effects are explored to capture the microbial ecology interactions and environmental factors affecting the media ecosystem. The findings of reviewed studies concurred in identifying Proteobacteria as the most dominant phylum. However, Proteobacteria and other phyla relative abundance differ substantially depending upon environmental factors (e.g., pH, temperature, nutrients availability, among others) gradients. In general, we found significant gaps to relate and explain the biodegradation performance and metabolic processes within the biofilter, and hence deserve future attention. We highlighted and identified key challenges and future research ideas to assure O₃-biofiltration reliability as a promising barrier in advanced water treatment applications.

Antibiotic and Disinfectant Resistance in Tap Water Strains - Insight into the Resistance of Environmental Bacteria

Although antibiotic-resistant bacteria (ARB) have been isolated from tap water worldwide, the knowledge of their resistance patterns is still scarce. Both horizontal and vertical gene transfer has been suggested to contribute to the resistance spread among tap water bacteria. In this study, ARB were isolated from finished water collected at two independent water treatment plants (WTPs) and tap water collected at several point-of-use taps during summer and winter sampling campaigns. A total of 24 strains were identified to genus or species level and subjected to antibiotic and disinfectant susceptibility testing. The investigated tap water ARB belonged to phyla Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes. The majority of the isolates proved multidrug resistant and resistant to chemical disinfectant. Neither seasonal nor WTP-dependent variabilities in antibiotic or disinfectant resistance were found. Antibiotics most effective against the investigated isolates included imipenem, tetracyclines, erythromycin, and least effective - aztreonam, cefotaxime, amoxicillin, and ceftazidime. The most resistant strains originate from Afipia sp. and Methylobacterium sp. Comparing resistance patterns of isolated tap water ARB with literature reports concerning the same genera or species confirms intra-genus or even intra-specific variabilities of environmental bacteria. Neither species-specific nor acquired resistance can be excluded.

Impact of phosphate dosing on the microbial ecology of drinking water distribution systems: Fieldwork studies in chlorinated networks

Phosphate is routinely dosed to ensure regulatory compliance for lead in drinking water distribution systems. Little is known about the impact of the phosphate dose on the microbial ecology in these systems and in particular the endemic biofilms. Disturbance of the biofilms and embedded material in distribution can cause regulatory failures for turbidity and metals. To investigate the impact of phosphate on developing biofilms, pipe wall material from four independent pipe sections was mobilised and collected using two twin-flushing operations a year apart in a chlorinated UK network pre- and post-phosphate dosing. Intensive monitoring was undertaken, including turbidity and water physico-chemistry, traditional microbial culture-based indicators, and microbial community structure via sequencing the 16S rRNA gene for bacteria and the ITS2 gene for fungi. Whole metagenome sequencing was used to study shifts in functional characteristics following the addition of phosphate. As an operational consequence, turbidity responses from the phosphate-enriched water were increased, particularly from cast iron pipes. Differences in the taxonomic composition of both bacteria and fungi were also observed, emphasising a community shift towards microorganisms able to use or metabolise phosphate. Phosphate increased the relative abundance of bacteria such as Pseudomonas, Paenibacillus, Massilia, Acinetobacter and the fungi Cadophora, Rhizophagus and Eupenicillium. Whole metagenome sequencing showed with phosphate a favouring of sequences related to Gram-negative bacterium type cell wall function, virions and thylakoids, but a reduction in the number of sequences associated to vitamin binding, methanogenesis and toxin biosynthesis. With current faecal indicator tests only providing risk detection in bulk water samples, this work improves understanding of how network changes effect microbial ecology and highlights the potential for new approaches to inform future monitoring or control strategies to protect drinking water quality.

Efficacy and Effectiveness of Showerheads Attached with Point-of-use (POU) Filter Capsules in Preventing Waterborne Diseases in a Japanese Hospital

Tap water contamination is a growing concern in healthcare facilities, and despite chlorination, tap water in these facilities contains several pathogenic microorganisms causing healthcare-associated waterborne infections or nosocomial outbreaks. Shower units are particularly prone to contamination as they are conducive for bacterial growth and can even produce bioaerosols containing pathogenic bacteria. Shower units coupled with point-of-use (POU) water filters are a simple and safe option; however, their efficacy has been under-reported. Therefore, we determined the efficacy of showerheads attached with a POU filter capsule in preventing infections in our hospital. We investigated the presence of pathogenic bacteria in water sampled from three shower units. After replacing the original shower units with new ones incorporated with a sterile-grade water filter capsule (0.2 µm; QPoint™), the water samples were analyzed for up to 2 months. The POU filters removed several pathogenic bacteria (Mycobacterium, Pseudomonas, Stenotrophomonas, Aeromonas, and Klebsiella spp.). Filter effectiveness depends on regional water quality and we believe that effective tap water treatment combined with the use of POU filters (introduced at a reasonable cost in healthcare facilities) can considerably minimize waterborne diseases in hospitals and improve patient care.

Evolution of gentamicin and arsenite resistance acquisition in Ralstonia pickettii water isolates

Ralstonia pickettii are ubiquitous in water environments. Members of this species are frequently, but not always, resistant to both gentamicin and arsenite. Gentamicin and arsenite co-resistance and the putative molecular mechanisms were investigated. A group of 37 R. pickettii strains isolated from drinking water and hospital wastewater were characterized for gentamicin and arsenite resistance phenotypes, the number and size of plasmids, and screened for genetic elements associated with arsenite tolerance, Integrative and Conjugative Elements (ICEs), among other. The genomes of three representative strains were compared. Most gentamicin resistant (GR) isolates (32/33) were resistant to arsenite, and harbored ICE- and ars operon-related genes. These genetic elements were not detected in any of the five arsenite susceptible strains, regardless of the GR (n = 1) or gentamicin susceptibility (GS) (n = 4) phenotype. The comparison of the genomes of two GR (one resistant and one susceptible to arsenite) and one GS strains suggested that these phenotypes correspond to three phylogroups, distinguished by presence of some genes only in GR isolates, in addition to point mutations in functional genes. The presence of ICEs and ars operon-related genes suggest that arsenite resistance might have been acquired by GR lineages.

Acinetobacter spp. in food and drinking water - A review

Acinetobacter spp. has emerged as a pathogen of major public health concern due to their increased resistance to antibiotics and their association with a wide range of nosocomial infections, community-acquired infections and war and natural disaster-related infections. It is recognized as a ubiquitous organism however, information about the prevalence of different pathogenic species of this genus in food sources and drinking water is scarce. Since the implementation of molecular techniques, the role of foods as a source of several species, including the Acinetobacter baumannii group, has been elucidated. Multidrug resistance was also detected among Acinetobacter spp. isolated from food products. This highlights the importance of foods as potential sources of dissemination of Acinetobacter spp. between the community and clinical environments and reinforces the need for further investigations on the potential health risks of Acinetobacter spp. as foodborne pathogens. The aim of this review was to summarize the published data on the occurrence of Acinetobacter spp. in different food sources and drinking water. This information should be taken into consideration by those responsible for infection control in hospitals and other healthcare facilities.

Spatiotemporal Changes of Antibiotic Resistance and Bacterial Communities in Drinking Water Distribution System in Wrocław, Poland

Antibiotic resistance of bacteria is an emerging problem in drinking water treatment. This paper presents the comparison of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) prevalence during the summer and winter season in a full-scale drinking water distribution system (DWDS) supplied by two water treatment plants (WTPs). The effect of distance from WTP and physical–chemical water parameters on its microbial properties was also tested. Bacterial consortia dwelling in bulk tap water were additionally compared by means of denaturating gradient gel electrophoresis (DGGE). The results showed that among ARB, bacteria resistant to ceftazidime (CAZ) were the most abundant, followed by bacteria resistant to amoxicillin (AML), ciprofloxacin (CIP), and tetracycline (TE). Numerous ARGs were detected in tested tap water samples. Only CAZ resistant bacteria were more prevalent in the season of increased antibiotic consumption, and only AML resistant bacteria relative abundances increase was statistically significant with the distance from a WTP. The investigated tap water meets all legal requirements. It is therefore safe to drink according to the law. Nevertheless, because antibiotic resistance could pose a threat to consumer health, it should be further monitored in DWDSs.

Genetic and physiological analysis of biofilm formation on different plastic surfaces by Sphingomonas sp. strain S2M10 reveals an essential function of sphingan biosynthesis

Alphaproteobacteria belonging to the group of the sphingomonads are frequently found in biofilms colonizing pure-water systems, where they cause technical and hygienic problems. In this study, physiological properties of sphingomonads for biofilm formation on plastic surfaces were analysed. Sphingomonas sp. strain S2M10 was isolated from a used water-filtration membrane and submitted to transposon mutagenesis for isolating mutants with altered biofilm formation. Mutants showing strongly decreased biofilm formation carried transposon insertions in genes for the biosynthesis of the polysaccharide sphingan and for flagellar motility. Flagella-mediated attachment was apparently important for biofilm formation on plastic materials of intermediate hydrophobicity, while a mutant with defect in spnB, encoding the first enzyme in sphingan biosynthesis, showed no biofilm formation on all tested materials. Sphingan-dependent biofilm formation was induced in the presence of specific carbon sources while it was not induced in complex medium with yeast extract and tryptone. The regulation of sphingan-based biofilm formation was investigated by interfering with the CckA/ChpT/CtrA phosphorelay, a central signal-transduction pathway in most Alphaproteobacteria. Construction and ectopic expression of a kinase-deficient histidine kinase CckA caused cell elongation and massive sphingan-dependent cell aggregation. In addition, it caused increased activity of the promotor of spnB. In conclusion, these results indicate that sphingan-based biofilm formation by sphingomonads might be triggered by specific carbon sources under prototrophic conditions resembling a milieu that often prevails in pure-water systems.