Water Microbial Communities Research Articles

Bio-degumming of ramie fiber using an integrated spiral symmetry stream anaerobic bioreactor

The bio-degumming method focused research interest on green degumming technology in the textile sector, addressing environmental pollution, water usage and energy consumption caused by chemical degumming methods while enhancing fiber quality. The application of recent developments in the chemical degumming method of fiber remains a challenge for environmental protection. The novel spiral symmetry stream anaerobic bioreactor was employed in a system that integrates the ramie degumming process and reduces wastewater generation. This study analyzed the effect of liquor ratios on the water quality indicators, fiber quality and microbial community composition. After this study, the effluent chemical oxygen demand concentration, pH and ammonia nitrogen were 264.2 ± 114.2, 7.2 ± 0.1 and 7.4 ± 4.8 mg/L, respectively. This shows a mean chemical oxygen demand removal rate of 55.7 ± 11.8%, which is over 79% higher than previous bio-degumming methods. The fiber quality met the ramie fine dry hemp standard requirements. The high-throughput sequencing results revealed that the microbial community adapted to this process. The relative abundance of dominant microbes ( Bacteroidetes and Methanosaeta), which perform biodegradation and methane production, was present. This study demonstrates a promising green degumming technology and eco-friendly concept for the textile industry.

Cyanobacterial blooms control with CaO2 in different stages: Inhibition efficiency, water quality optimization and microbial community changes

This study explored the feasibility of calcium peroxide (CaO2) to inhibit cyanobacterial blooms of the outbreak and dormancy stages. Our previous studies have found that CaO2 has a high inhibitory effect on cyanobacteria. In order to explore the application effect of CaO2 in actual cyanobacteria lake water, we conducted this study to clarify the effect of CaO2 on inhibiting cyanobacteria in outbreak and dormancy stages. The results showed that CaO2 inhibited the growth of cyanobacteria in the outbreak and dormancy stages by 98.7% and 97.6%, respectively. The main inhibitory mechanism is: (1) destroy the cell structure and make the cells undergo programmed cell death by stimulating the oxidation balance of cyanobacteria cells; (2) EPS released by cyanobacteria resist stimulation and combine calcium to form colonies, and accelerate cell settlement. In addition to causing direct damage to cyanobacteria, CaO2 can also improve water quality and sediment microbial diversity, and reduce the release of sediment to phosphorus, so as to further contribute to cyanobacterial inhibition. Finally, the results of qRT-PCR analysis confirmed the promoting effect of CaO2 on the downregulation of photosynthesis-related genes (rbcL and psaB), microcystn (mcyA and mcyD) and peroxiredoxin (prx), and verified the mechanism of CaO2 inhibition of cyanobacteria. In conclusion, this study provides new findings for the future suppression of cyanobacterial bloom, by combining water quality, cyanobacterial inhibition mechanisms, and sediment microbial diversity.

Macrophyte coverage drives microbial community structure and interactions in a shallow sub-tropical lake

Shallow lakes are typically dominated by macrophytes, which have important functional roles regulating trophic conditions and creating biological habitat. Macrophytes have been shown to strongly influence water chemistry and shape microbial communities in shallow lakes. In Florida, many large, shallow lakes are dominated by alien invasive, submersed macrophytes, such as hydrilla (Hydrilla verticillata [L.F.] Royle) and are intensively managed to reduce infestations and contain the spread of these alien invasive macrophytes. In this study, we investigated the effects of large (40 ha) herbicidal and mechanical control treatments on a large lake located in Central Florida that resulted in the reduction of Hydrilla and concomitant changes in water chemistry and microbial communities (both bacteria and protists [microbial eukaryotes]). We observed a considerable decrease in macrophyte coverage associated with plant control treatments as well as a temporal change in macrophyte coverage in Lake Tohopekaliga. We found that changes in macrophyte coverage, regardless of treatment type, significantly affected the water chemistry of the lake, resulting in a sharp increase of chlorophyll a concentration as well as an increase in turbidity with the decrease of macrophyte coverage. Moreover, the decline in macrophytes led to decreases in microbial community diversity with over-representation of phototrophic functional groups. Specifically, we observed an increase in cyanobacteria with the decrease in macrophyte coverage. Our study highlights the advantages and disadvantages of macrophyte control. Although there was an initial decrease in macrophyte coverage associated with the chemical and mechanical control of aquatic plants, after a few months, we found a considerable increase in coverage. In addition, the increase of cyanobacterial relative abundance demonstrates the possible consequences of aquatic plant control such as cyanobacterial blooms if there is a continued decline of macrophytes.

Recent advancement on water filtration membranes: Navigating biofouling challenges

This study investigates the field of antifouling membranes for water filtration and desalination applications, specifically focusing on two-dimensional materials. The study examines the importance of these membranes in the context of climate change and its effects on coastal ecosystems. The occurrence of biofouling in seawater desalination membranes is closely connected to intricate processes influenced by factors such as water quality, microbial communities, hydrodynamics, and membrane properties. Microorganism adhesion initiates the process, which then advances into irreversible attachment and the creation of biofilm. Detached pieces contribute to the perpetuation of fouling. Biofouling is caused by a variety of biomaterials and organics, including bacteria, extracellular polymeric substances (EPS), proteins, and humic compounds. Innovative methods such as surface alterations using two-dimensional materials like graphene and graphene oxide, as well as the use of biofouling-resistant materials, provide promising possibilities. These materials have antifouling characteristics, making them environmentally beneficial options that reduce the need for chemical cleaning. Their application improves the water treatment process by preventing fouling and enhancing membrane performance. Real-world research applications can enhance and optimize these tactics to effectively reduce biofouling in seawater desalination systems, hence improving efficiency and sustainability. This is particularly important in light of climate change and its impact on coastal ecosystems. The findings obtained from the literature review emphasise the utmost significance of tackling biofouling in the face of a changing environment, particularly with regard to microorganisms. Important factors to consider are the selection of coating materials, the implementation of environmentally friendly cleaning solutions made from natural chemicals, and the improvement of pretreatment systems. Green cleaning agents are important eco-friendly alternatives to typical biocides, as they possess antibacterial, antifungal, and antifouling capabilities. Given the existence of climate change, these observations serve as a basis for promoting environmentally friendly methods in water treatment technology.

Effects of running time on biological activated carbon filters: water purification performance and microbial community evolution.

Ozone-biologically activated carbon (BAC) filtration is an advanced treatment process that can be applied to remove recalcitrant organic micro-pollutants in drinking water treatment plants (DWTPs). In this study, we continuously monitored a new and an old BAC filter in a DWTP for 1year to compare their water purification performance and microbial community evolution. The results revealed that, compared with the new filter, the use of the old BAC filter facilitated a slightly lower rate of dissolved organic carbon (DOC) removal. In the case of the new BAC filter, we recorded general increases in the biomass and microbial diversity of the biofilm with a prolongation of operating time, with the biomass stabilizing after 7months. For both new and old BAC filters, Proteobacteria and Acidobacteria were the dominant bacterial phyla. At the genus level, the microbial community gradually shifted over the course of operation from a predominance of Herminiimonas and Hydrogenophaga to one predominated by Bradyrhizbium, Bryobacter, Hyphomicrobium, and Pedomicrobium, with Bradyrhizobium being established as the most abundant genus in the old BAC filter. Regarding spatial distribution, we detected reductions in the biomass and number of operational taxonomic units with increasing biofilm depth, whereas there was a corresponding increase in microbial diversity. However, compared with the effects of time, the influence of depth on the composition of the biofilm microbial community was considerably smaller. Furthermore, co-occurrence network analysis revealed that the microbial community network of the new filter after 11months of operation was the most tightly connected, although its modular coefficient was the lowest of those assessed. We speculate that the positive and negative interactions within the network may be attributable to symbiotic or competitive relationships among species. Moreover, there may have been a significant negative interaction between SWB02 and Acidovorax, plausibly associated with a competition for substrates.

Treatment of formaldehyde-containing wastewater and power generation by constructed wetland–microbial fuel cells enhanced by formaldehyde-degrading bacteria

In this study, three formaldehyde-degrading bacteria, Paenibacillus, Hyphomicrobium, and Ensifer were isolated from activated sludge. Three strains of formaldehyde-degrading bacteria were enriched and added to a constructed wetland–microbial fuel cells (CW-MFC) for bioaugmentation. Three laboratory-scale devices were built: constructed wetland (CW), enhanced CW-MFC (EG), and non-enhanced CW-MFC (CG). During the 70 days of operation, a comprehensive study was conducted to investigate the impact of bioaugmentation on the performance of CW-MFC in treating formaldehyde wastewater, considering water quality, power generation, and microbial communities. The formaldehyde removal rate by the EG (98.8 % ± 0.6 %) was significantly higher than that of the CG (91.0 % ± 0.6 %) (P < 0.05). The average voltage of the EG (167.3 ± 4.8 mV) was higher than the CG (122.5 ± 2.9 mV). Bioaugmentation of a constructed wetland–microbial fuel cell can significantly improve its ability to treat formaldehyde-containing wastewater and generate electricity.

Metagenomic insights into the impact of litter from poultry Concentrated Animal Feeding Operations (CAFOs) to adjacent soil and water microbial communities

In recent decades, human food consumption has led to an increased demand for animal-based foods, particularly chicken meat production. The state of Georgia, USA is one of the top broiler chicken producers in the United States, where animals are raised in Concentrated Animal Feeding Operations (CAFOs). Without proper management, CAFOs could negatively impact the environment and become a public health risk as a source of water and air pollution and/or by spreading antimicrobial resistance genes. In this study, we used metagenome sequencing to investigate the impact of the application of the CAFO's litter on adjacent soils and downstream creek waters in terms of microbial diversity and antimicrobial resistance profile changes. Our data indicate that while a few microbial groups increased in abundance within a short period of time after litter application, these populations subsequently decreased to levels similar to those found prior to the litter application or to below the detection limit of our metagenome sequencing effort. Microbial taxonomic composition analyses, relative abundance of Metagenome-Assembled Genomes (MAGs) and detection of Antimicrobial Resistance Genes (ARGs) allow us to conclude that this practice of litter application had a negligible effect on the microbiome or resistome profile of these soils and nearby waterways, likely due to its dilution in the field and/or outcompetition by indigenous microbes, revealing a minimal impact of these poultry facilities on the natural microbial communities.

Characteristics of Groundwater Microbial Community Composition and Environmental Response in the Yimuquan Aquifer, North China Plain

To explore the intricate interrelationship between groundwater microbial communities and hydrochemical characteristics in the Mancheng District, Baoding City, samples from karst groundwater and porous groundwater were collected. Hydrochemical analysis and the 16s RNA gene V4-V5 region sequencing method were used to detail the water environmental characteristics and microbial community distribution pattern in the study area. The hydrochemical results reveal notable differences in major ion contents and other hydrochemical indices between karst water and porous water. Microbial community analysis demonstrates that Proteobacteria, Actinobacteria, and Firmicutes are the dominant taxa in both types of water bodies, albeit with significant variations in their proportions across distinct water bodies. The observed disparities in microbial communities between karst water and porous water underscore the influence of environmental factors such as ion concentration and pH on microbial distribution. Redundancy Analysis (RDA) indicates notable associations between microbial community composition and environmental factors in both types of groundwater environments. Studying the distribution pattern of microbial communities and the connection with environmental factors in two types of groundwater lays a crucial foundation for interpreting the functional roles of microbes in groundwater ecosystems.

Spatiotemporal structure and composition of the microbial communities in hypersaline Lake Magadi, Kenya

Background Soda lakes are habitats characterized by haloalkaline conditions also known to host unique microbial communities. The water chemistry changes with seasons due to evaporative concentration or floods from the surrounding grounds. However, it is not yet clear if the change in physiochemical changes influences the spatiotemporal diversity and structure of microbial communities in these ecosystems. Methods This study investigated the spatiotemporal diversity and structure of microbial communities in water and brine samples collected from hypersaline Lake Magadi in the months of June–September 2018. Amplicons were generated using Illumina sequencing of the 16S rRNA gene. Results The abundant bacterial phyla were Proteobacteria, Cyanobacteria, Bacteroidetes, Actinobacteria, Firmicutes, Verrumicrobia, Deinococcus-Thermus, Spirochaetes, and Chloroflexi. The Archaeal diversity was represented by phyla Euryachaeota, Crenarchaeota, Euryarchaeota, and Thaumarchaeota. The dominant bacterial species were: Euhalothece sp. (10.3%), Rhodobaca sp. (9.6%), Idiomarina sp. (5.8%), Rhodothermus sp. (3.0%), Roseinatronobacter sp. (2.4%), Nocardioides sp. (2.3%), Gracilimonas sp. (2.2%), and Halomonas sp. (2%). The dominant archaeal species included Halorubrum sp. (18.3%), Salinarchaeum sp. (5.3%), and Haloterrigena sp. (1.3%). The composition of bacteria was higher than that of archaea, while their richness and diversity varied widely across the sampling seasons. The α-diversity indices showed that high diversity was recorded in the month of August, followed by September, June, and July in that order. Furthermore, salinity and alkalinity affect β-diversity rather than the sampling site or seasonality. The effects of physicochemical parameters on the microbial community structure showed that temperature, pH, P+, K+, NO3 -, and total dissolved solids (TDS) had a positive correlation with the microbial community structure. Multivariate analysis revealed significant spatial and temporal effects on β-diversity and salinity and alkalinity were the major drivers of microbial composition in Lake Magadi. Conclusions We provide insights into the relationships between microbial communities and geochemistry across various sampling sites in Lake Magadi.

Water and sediment microbial communities in shallow coastal ecosystems of Lake Baikal during summer 2021-2022

The taxonomical structure of the microbial community of shallow coastal areas is closely related to environmental conditions, and also changes rapidly in response to changes determined by water level fluctuations. The taxonomic structure of microbial communities in the shallow coastal areas of the Lake Baikal was studied during the period of high water level in summer months 2021-2022. At the phylum level, Proteobacteria, Actinobacteriota, Bacteroidota, Firmicutes, Cyanobacteria, Verrucomicrobiota and Deinococcota were dominant, accounting for 98.55 to 99.46% of the total microbial diversity in water microbial community. A significant similarity was revealed in the taxonomic composition of microbial communities in the shallow coastal areas of the Lake Baikal during certain summer months of 2021-2022. Similar water microbial communities formed in June 2021/22; in July 2022 in the Enkhaluk and Sukhaya sample sites, as well as at the Goryachinsk and Sukhaya sample sites in August 2022. Sediment microbial communities were dominated by Gammaproteobacteria, Bacteroidota, Alphaproteobacteria, Actinobacteriota and Verrucomicrobiota.

The stress response mechanisms and resistance change of chlorine-resistant microbial community at multi-phase interface under residual antibiotics in drinking water distribution system

The presence of multiple trace amounts of antibiotics in drinking water has recently drawn much attention. However, synergistic effects between disinfectants and antibiotics often occur in pipeline due to the presence of residual disinfectants. How this interaction affects the drinking water microbial community remains unknown. Herein, reactors with 2 h of hydraulic retention time (HRT) were constructed to simulate the drinking water distribution system (DWDS), and the antibiotics were continuously discharged to the reactor. Sulfamethoxazole (SMX) was used as a representative antibiotic, and treatment protocols with and without disinfectants were compared. High-throughput sequencing and metagenome were used to study the microbial community and function in polyethylene (PE) and ductile cast iron (DI) (protected by cement mortar lining) pipes. By measuring the enzyme activity and ATP content, we found that disinfectant exposure could not only increase the secretion of biofilm EPS, but also improve the bacterial activity to a certain extent. The synergistic effect of antibiotics and disinfectants could increase the activity of oxidative stress-related enzymes in microbial communities, and the main effect was antibiotic stress. This study not only provides insights into how to inhibit the transmission process of antibiotic resistance genes (ARGs) in biofilm in DWDS, but also provides enlightenment for the harm of ARGs in all carriers where biofilms may exist in water plants.

Microbial methane formation in deep aquifers associated with the sediment burial history at a coastal site

Abstract. Elucidating the mechanisms underlying microbial methane formation in subsurface environments is essential to understanding the global carbon cycle. This study examined how microbial methane formation (i.e., methanogenesis) occurs in natural-gas-bearing sedimentary aquifers throughout the sediment burial history. Water samples collected from six aquifers of different depths exhibited ascending vertical gradients in salinity from brine to fresh water and in temperature from mesophilic to psychrophilic conditions. Analyses of gas and water isotopic ratios and microbial communities indicated the predominance of methanogenesis via CO2 reduction. However, the hydrogen isotopic ratio of water changed along the depth and salinity gradient, whereas the ratio of methane changed little, suggesting that in situ methanogenesis in shallow sediments does not significantly contribute to methane in the aquifers. The population of methane-producing microorganisms (methanogens) was highest in the deepest saline aquifers, where the water temperature, salinity, and total organic carbon content of the adjacent mud sediments were the highest. Cultivation of the dominant hydrogenotrophic methanogens in the aquifers showed that the methanogenesis rate was maximized at the temperature corresponding to that of the deepest aquifer. These results suggest that high-temperature conditions in deeply buried sediments are associated with enhanced in situ methanogenesis and that methane that forms in the deepest aquifer migrates upward into the shallower aquifers by diffusion.

Interactions between water quality and microbes in epiphytic biofilm and superficial sediment of lake in trophic agriculture area

Epiphytic and superficial sediment biofilm-dwelling microbial communities play a pivotal role in water quality regulation and biogeochemical cycling in shallow lakes. However, the interactions are far from clear between water physicochemical parameters and microbial community on aquatic plants and in surface sediments of lake in trophic agriculture area. This study employed Illumina sequencing, Partial Least Squares Path Modeling (PLS-PM), and physico-chemical analytical methods to explore the interactions between water quality and microbes (bacteria and eukaryotes) in three substrates of trophic shallow Lake Cyohoha North, Rwanda. The Lake Cyohoha was significantly polluted with total phosphorus (TP), total nitrogen (TN), nitrate nitrogen (NO3-N), and ammonia nitrogen (NH3−N) in the wet season compared to the dry season. PLS-PM revealed a strong positive correlation (+0.9301) between land use types and physico-chemical variables in the rainy season. In three substrates of the trophic lake, Proteobacteria, Cyanobacteria, Firmicutes, and Actinobacteria were dominant phyla in the bacterial communities, and Rotifers, Platyhelminthes, Gastrotricha, and Ascomycota dominated in microeukaryotic communities. As revealed by null and neutral models, stochastic processes predominantly governed the assembly of bacterial and microeukaryotic communities in biofilms and surface sediments. Network analysis revealed that the microbial interconnections in Ceratophyllum demersum were more stable and complex compared to those in Eichhornia crassipes and sediments. Co-occurrence network analysis (|r| > 0.7, p < 0.05) revealed that there were complex interactions among physicochemical parameters and microbes in epiphytic and sediment biofilms, and many keystone microbes on three substrates played important role in nutrients removal, food web and microbial community stable. These findings emphasize that eutrophic water influence the structure, composition, and interactions of microbes in epiphytic and surface sediment biofilms, and provided new insights into the interconnections between water quality and microbial community in presentative substrates in tropical lacustrine ecosystems in agriculturally polluted areas. The study provides useful information for water quality protection and aquatic plants restoration for policy making and catchment management.

Assembly mechanisms of microbial communities in plastisphere related to species taxonomic types and habitat niches

A lot of plastic floats are presented in the kelp cultivation zone, enabling us to effectively evaluate the differences between surface water (SW) and plastic-attached (PA) microbial communities. In this study, we explored the microbial communities (both bacteria and protists) in SW and PA niches during the kelp cultivation activities. Effects of habitat niches on the diversity and composition of microbial communities were found. Beta partitioning and core taxa analyses showed species turnover and local species pool governed the microbial community assembly, and they contributed more to bacteria and protists, respectively. Based on the results of null model, bacterial communities presented a more deterministic and homogeneous assembly compared to protistan communities. Moreover, microbial communities in PA niche had higher species turnover and homogenizing assembly compared to the SW niche. The results of this study supplemented the theory of microbial community assembly and expanded our understanding of protists in plastisphere.

Methane emission from water level fluctuation zone of the Three Gorges Reservoir: Seasonal variation and microbial mechanism

Periodic and significant water level fluctuations within the Three Gorges Reservoir (TGR) create a complex water level fluctuation zone (WLFZ) that can significantly influence greenhouse gas emissions. However, the scarcity of comprehensive studies investigating long-term monitoring and analysis of CH4 flux patterns and underlying mechanisms concerning water level variations, environmental characteristics, and microbial communities has limited our understanding. This study conducted a four-year monitoring campaign to examine in situ CH4 emissions from three representative sampling sites. Results indicated that the CH4 flux remained relatively stable at lower water levels, specifically at the control site (S1). However, water level fluctuations significantly influenced CH4 emissions at the sampling sites situated within the WLFZ. Notably, the highest CH4 flux of 0.252 ± 0.089 mg/(m2·h) was observed during the drying period (June to August), while the lowest CH4 flux of 0.048 ± 0.026 mg/(m2·h) was recorded during the flooding period. Moreover, CH4 emissions through the water-air interface surpassed those through the soil-air interface. The CH4 flux positively correlated with organic carbon, temperature, and soil moisture. The relative abundance of methane metabolism microorganisms peaked during the drying period and decreased during the impounding and flooding periods. The primary methanogenesis pathway was hydrogenotrophic, whereas methanotrophic processes were mainly aerobic, with Ca. Methylomirabilis governing the anaerobic methanotrophic process. Overall, the current findings serve as crucial theoretical references for understanding CH4 emissions and carbon metabolism processes within WLFZ environments.

Analysis of Microbial Community in Circulating Cooling Water System of Coal Power Plant during Reagent Conversion

The use of phosphorus-containing chemical corrosion and scale inhibitors has been found to result in excessive phosphorus discharge and an inability to reduce the high concentration of CODcr in the circulating cooling water, thereby making it challenging to comply with increasingly stringent sewage discharge standards. This study aims to assess the practicality of utilizing biological corrosion and scale inhibitors in coal power plants’ operation, as well as investigating the correlation between water quality indicators and microbial communities during the conversion period. The data illustrates that, in comparison to the chemical method, there is a decrease in turbidity of the circulating water from 19.44 NTU to 9.60 NTU, a reduction in CODcr from 71.55 mg/L to 45.47 mg/L, and a drop in TP from 2.35 mg/L to 0.38 mg/L. Microbial community analysis during the transition period reveals that microorganisms rapidly establish a new equilibrium in the circulating water, sediment, and fiber ball, resulting in significantly different microbial community structures. The relative abundance of corrosive microorganisms such as Flavobacterium, Pedomicrobium, and Hydrogenophaga is significantly diminished in the circulating water, whilst the abundance of anaerobic microorganisms like Anaerolineaceae and Rhodopseudomonas in the sediment also declines. Conversely, there is an increased presence of microorganisms associated with contaminant degradation, such as CL500-3 and SM1A02. These findings suggest a decrease in the risk of system corrosion and an enhancement in contaminant degradation capability. This study provides evidence supporting the replacement of chemical agents with biological agents in circulating cooling water systems, contributing to more environmentally friendly and sustainable practices.

The combination of multiple environmental stressors strongly alters microbial community assembly in aquatic ecosystems

Microorganisms play a critical role in maintaining the delicate balance of ecosystem services. However, the assembly processes that shape microbial communities are vulnerable to a range of environmental stressors, such as climate change, eutrophication, and the use of herbicides. Despite the importance of these stressors, little is known about their cumulative impacts on microbial community assembly in aquatic ecosystems. To address this knowledge gap, we established 48 mesocosm experiments that simulated shallow lake ecosystems and subjected them to warming (including continuous warming (W) and heat waves (H)), glyphosate-based herbicides (G), and nutrient loading (E). Our study revealed that in the control group, both deterministic and stochastic processes codominated the assembly of microbial communities in water, whereas in sediment, the processes were primarily stochastic. Interestingly, the effects of multiple stress factors on assembly in these two habitats were completely opposite. Specifically, stressors promoted the dominance of stochastic processes in water but increased the importance of deterministic processes in sediment. Furthermore, warming amplified the effects of herbicides but exerted an opposite and stronger influence on assembly compared to nutrients, emphasizing the complexity of these mechanisms and the significance of considering multiple stressors. The interaction of some factors significantly affected assembly (p < 0.05), with the effects of WEG being most pronounced in water. Both water and sediment exhibited homogeneous assembly of microbial communities (mean NTI >0), but the phylogenetic clustering of microbial communities in water was more closely related (NTI >2). Our research revealed the response model of microbial community assembly in aquatic ecosystems to multiple environmental stresses, such as agricultural pollution, climate change, and eutrophication, and indicated that microbial community changes in sediment may be an important predictor of lake ecosystem development. This provides scientific evidence that better environmental management can reduce impacts on aquatic ecosystems under the threat of future warming.

Assessing the Impacts of Lead Corrosion Control on the Microbial Ecology and Abundance of Drinking-Water-Associated Pathogens in a Full-Scale Drinking Water Distribution System.

Increases in phosphate availability in drinking water distribution systems (DWDSs) from the use of phosphate-based corrosion control strategies may result in nutrient and microbial community composition shifts in the DWDS. This study assessed the year-long impacts of full-scale DWDS orthophosphate addition on both the microbial ecology and density of drinking-water-associated pathogens that infect the immunocompromised (DWPIs). Using 16S rRNA gene amplicon sequencing and droplet digital PCR, drinking water microbial community composition and DWPI density were examined. Microbial community composition analysis suggested significant compositional changes after the orthophosphate addition. Significant increases in total bacterial density were observed after orthophosphate addition, likely driven by a 2 log 10 increase in nontuberculous mycobacteria (NTM). Linear effect models confirmed the importance of phosphate addition with phosphorus concentration explaining 17% and 12% of the variance in NTM and L. pneumophila density, respectively. To elucidate the impact of phosphate on NTM aggregation, a comparison of planktonic and aggregate fractions of NTM cultures grown at varying phosphate concentrations was conducted. Aggregation assay results suggested that higher phosphate concentrations cause more disaggregation, and the interaction between phosphate and NTM is species specific. This work reveals new insight into the consequences of orthophosphate application on the DWDS microbiome and highlights the importance of proactively monitoring the DWDS for DWPIs.

Microplastics and chemical leachates from plastic pipes are associated with increased virulence and antimicrobial resistance potential of drinking water microbial communities

There is increasing recognition of the potential impacts of microplastics (MPs) on human health. As drinking water is the most direct route of human exposure to MPs, there is an urgent need to elucidate MPs source and fate in drinking water distribution system (DWDS). Here, we showed polypropylene random plastic pipes exposed to different water quality (chlorination and heating) and environmental (freeze-thaw) conditions accelerated MPs generation and chemical leaching. MPs showed various morphology and aggregation states, and chemical leaches exhibited distinct profiles due to different physicochemical treatments. Based on the physiological toxicity of leachates, oxidative stress level was negatively correlated with disinfection by-products in the leachates. Microbial network analysis demonstrated exposure to leachates (under three treatments) undermined microbial community stability and increased the relative abundance and dominance of pathogenic bacteria. Leachate physical and chemical properties (i.e., MPs abundance, hydrodynamic diameter, zeta potential, total organic carbon, dissolved ECs) exerted significant (p < 0.05) effects on the functional genes related to virulence, antibiotic resistance and metabolic pathways. Notably, chlorination significantly increased correlations among pathogenic bacteria, virulence genes, and antibiotic resistance genes. Overall, this study advances the understanding of direct and indirect risks of these MPs released from plastic pipes in the DWDS.

Effects of salinity and betaine addition on anaerobic granular sludge properties and microbial community succession patterns in organic saline wastewater

In this study, the effects of different salinity gradients and addition of compatible solutes on anaerobic treated effluent water qualities, sludge characteristics and microbial communities were investigated. The increase in salinity resulted in a decrease in particle size of the granular sludge, which was concentrated in the range of 0.5-1.0 mm. The content of EPS (extracellular polymeric substances) in the granular sludge gradually increased with increasing salinity and the addition of betaine (a typical compatible solute). Meanwhile, the microbial community structure was significantly affected by salinity, with high salinity reducing the diversity of bacteria. At higher salinity, Patescibacteria and Proteobacteria gradually became the dominant phylum, with relative abundance increasing to 13.53% and 12.16% at 20 g/L salinity. Desulfobacterota and its subordinate Desulfovibrio, which secrete EPS in large quantities, dominated significantly after betaine addition.Their relative abundance reached 13.65% and 7.86% at phylum level and genus level. The effect of these changes on the treated effluent was shown as the average chemical oxygen demand (COD) removal rate decreased from 82.10% to 79.71%, 78.01%, 68.51% and 64.55% when the salinity gradually increased from 2 g/L to 6, 10, 16 and 20 g/L. At the salinity of 20 g/L, average COD removal increased to 71.65% by the addition of 2 mmol/L betaine. The gradient elevated salinity and the exogenous addition of betaine played an important role in achieving stability of the anaerobic system in a highly saline environment, which provided a feasible strategy for anaerobic treatment of organic saline wastewater.