Query: Drinking water biofilm microbial community

title: Influence of pipe materials on the microbial community in unchlorinated drinking water and biofilm.
abstract: Biodegradable compounds can cause undesired microbial growth in drinking water systems and these compounds can originate from the water or pipe materials used in drinking water systems. The aim of our study was to determine the influence of different pipe materials on the microbial populations in water and biofilm under semi stagnant conditions. The microbial communities in biofilm and water, which were in contact with seven different materials, were characterized by determining ATP concentrations, microbial composition gene copy numbers of some specific microbial groups. The ATP concentration in water and biofilm varied between the different materials with glass (negative control) copper PVCC PE Xc PE Xb PE 100 PVC P. Gene copy numbers of Legionella spp. Mycobacterium spp. Pseudomonas spp. Aeromonas spp. fungi and Vermamoeba vermiformis were also higher for PVC P and PE than for glass, copper and PVCC. The bacterial community composition in water and biofilm varied between materials as well. PERMANOVA and CAP analysis demonstrated that copper and PVC P are different when compared to the other materials. Furthermore, bacterial community composition and ATP concentrations in water and biofilm were similar after eight and 16 weeks incubation, but differed from results obtained after one week. Finally, the ATP, the specific microbial groups and the bacterial community composition also differed between water and biofilm on each material. We conclude from our study that pipe material is an important factor that influences the biomass concentration, abundance of specific microorganisms and the bacterial community composition in distribution systems with unchlorinated drinking water.

title: Characteristics of biostability of drinking water in aged pipes after water source switching: ATP evaluation, biofilms niches and microbial community transition.
abstract: Delivering quality changed water often contributes to the biological instability of drinking water distribution systems (DWDS) However, the potential effects of quality changed water on the biostability within DWDS are not well understood, especially after water switching to quality improved water. The objective of this study was to investigate the effects of quality improved water on DWDS, focusing on the stability of biofilm. The practical aged pipe was assembled into pipe reactors to simulate the effect of switching to quality improve water. The adenosine triphosphate (ATP) concentration of bulk water in the pipe reactors increased from ~1.2 ng/L to almost above 5 ng/L when fed water switching to TP 2. Biomass quantified by measuring ATP concentration confirmed that the risk of biofilm release through aged cast iron (CI) pipe surfaces after water source switching. The changes in water characteristics due to quality improved water source could cause bacteria release in DWDS at the initial period (at the first 7 days) However, the DWDS can establish the new stable phase after 42 days. Over time, biomass in the bulk water of the distribution system decreased significantly (The ATP concentration in the bulk maintains around 3 ng/L) after 42 days, indicating the improvement of water quality. The biofilm was dominated by bacteria related to iron cycling process, and at the genus level, Desulfovibrio had the highest relative abundance, however, it decreased significantly (from 48% to 9.3% after water source switching. And there was a slightly increase in the fraction of iron oxidizing bacteria (IOB) and siderophore producing bacteria (SPB) but a relatively higher increase in nitrate reducing bacteria (NRB) nitrobacteria (NOB) and iron reducing bacteria (IRB) was observed. Taken together, these results and the corrosion morphology, indicate that pipe biofilm and corrosion were chemically and microbially stable after re stability under water source switching. In addition, the bulk water environment showed a marked decrease in selected bacteria at genus level, including pathogenic species, indicating the improvement of quality in drinking water.

title: Prevalence of antibiotic resistance genes in drinking water and biofilms: The correlation with the microbial community and opportunistic pathogens.
abstract: The emergence of antibiotic resistance genes (ARGs) and opportunistic pathogens (OPs) in drinking water system posed potential risks to human health. However, the occurrence of ARGs and OPs in drinking water biofilms is still at its infancy. In this study, we investigated the occurrence of ARGs and OPs in both water and biofilm samples from a drinking water system, and the correlation between ARGs and microbial communities was analyzed. The quantitative PCR results showed that the drinking water treatment process effectively decreased the absolute abundances of ARGs. However, the relative concentration of ARGs did not show a significant difference between raw water and treated water samples. Compared with bulk water and tap water samples, biofilms had higher relative abundances of ARGs. 16 S Illumina Miseq sequencing results showed that microbial communities of biofilms were distinguished with water samples. Meanwhile, qPCR results of OPs also showed that biofilms had higher relative abundances of OPs compared with water samples. Furthermore, the Spearman correlation analysis indicated that Dechloromonas, Desulfovibrio, Methylobacterium and Propionivibrio correlated well with the relative abundance of ARGs. The absolute concentrations of OPs and ARGs also showed a significant correlation. Results of this study suggest that biofilms could serve as the reservoirs for the spread of ARGs and the interaction between biofilms and bulk water requires further research.

title: Impact of substrate material and chlorine/chloramine on the composition and function of a young biofilm microbial community as revealed by high throughput 16S rRNA sequencing.
abstract: The bacterial composition of biofilms in drinking water distribution systems is significantly impacted by the disinfection regime and substrate material. However, studies that have addressed the changes in the biofilm community during the early stage of formation (less than 10 weeks) were not yet adequate. Here, we explore the effects of the substrate materials (cast iron, stainless steel, copper, polyvinyl chloride, and high density polyethylene) and different disinfectants (chlorine and chloramine) on the community composition and function of young biofilm by using 16S rDNA sequencing. The results showed that Alphaproteobacteria (39.14% 80.87% and Actinobacteria (5.90% 40.03% were the dominant classes in chlorine disinfection samples, while Alphaproteobacteria (17.46% 74.18% and Betaproteobacteria (3.79% 68.50% became dominant in a chloraminated group. The infrequently discussed genus Phreatobacter became predominant in the chlorinated samples, but it was inhibited by chloramine and copper ions. The key driver of the community composition was indicated as different disinfectants according to principle coordination analysis (PCoA) and Permutational multivariate analysis of variance (Adonis test) and the bacterial community changed significantly over time. Communities of biofilms grown on cast iron showed a great distance from the other materials according to Bray Curtis dissimilarity, and they had a unique dominant genus, Dechloromonas. A metagenomics prediction based on 16S rDNA was used to detect the functional pathways of antibiotic biosynthesis and beta lactam resistance, and it revealed that several pathways were significantly different in terms of their chlorinated and chloraminated groups.

title: Assessing the origin of bacteria in tap water and distribution system in an unchlorinated drinking water system by SourceTracker using microbial community fingerprints.
abstract: The general consensus is that the abundance of tap water bacteria is greatly influenced by water purification and distribution. Those bacteria that are released from biofilm in the distribution system are especially considered as the major potential risk for drinking water bio safety. For the first time, this full scale study has captured and identified the proportional contribution of the source water, treated water, and distribution system in shaping the tap water bacterial community based on their microbial community fingerprints using the Bayesian "SourceTracker" method. The bacterial community profiles and diversity analyses illustrated that the water purification process shaped the community of planktonic and suspended particle associated bacteria in treated water. The bacterial communities associated with suspended particles, loose deposits, and biofilm were similar to each other, while the community of tap water planktonic bacteria varied across different locations in distribution system. The microbial source tracking results showed that there was not a detectable contribution of source water to bacterial community in the tap water and distribution system. The planktonic bacteria in the treated water was the major contributor to planktonic bacteria in the tap water (17.7 54.1% The particle associated bacterial community in the treated water seeded the bacterial community associated with loose deposits (24.9 32.7% and biofilm (37.8 43.8% in the distribution system. In return, the loose deposits and biofilm showed a significant influence on tap water planktonic and particle associated bacteria, which were location dependent and influenced by hydraulic changes. This was revealed by the increased contribution of loose deposits to tap water planktonic bacteria (from 2.5% to 38.0% and an increased contribution of biofilm to tap water particle associated bacteria (from 5.9% to 19.7% caused by possible hydraulic disturbance from proximal to distal regions. Therefore, our findings indicate that the tap water bacteria could possibly be managed by selecting and operating the purification process properly and cleaning the distribution system effectively.

title: Effects of bacterial community composition and structure in drinking water distribution systems on biofilm formation and chlorine resistance.
abstract: Community intrinsic properties affect the composition and function of a microbial community. Understanding the microbial community intrinsic properties in drinking water distribution systems (DWDS) could help to select disinfection strategies and aid in the prevention of waterborne infectious diseases. In this study, we investigated the formation of multi species biofilms in six groups, each consisting of four or five mixed bacterial strains isolated from a simulated DWDS, at different incubation times (24, 48, and 72 h) We then evaluated the chlorine resistance of the 72 h multi species biofilms in the presence of 0.3, 0.6, 1, 2, 4, and 10 mg/L residual chlorine. Microbacterium laevaniformans inhibited the formation of multi species biofilms, Sphingomonas sp. Acinetobacter sp. and A. deluvii had the effect of promoting their growth, and B. cereus has little effect on the growth of multi species biofilms. However, these inhibition and promotion effects were weak and inadequate to completely control the growth of multi species biofilms. All multi species produced strong biofilms after 72 h incubation, which could be due to microbial community intrinsic properties. Community intrinsic properties could maintain high EPS production and cell to cell connections in multi species biofilms, and could affect the formation of multi species biofilms. The chlorine resistance of multi species biofilms was significantly improved by B. cereus, but significantly reduced by M. laevaniformans. These results indicated that the microbial community intrinsic properties were influenced by the environment. At a relatively low disinfectant concentration <2 mg/L residual chlorine) the community intrinsic properties were maintained; however, when the disinfectant concentration was increased to 2 4 mg/L residual chlorine, the community intrinsic properties weakened, and significantly affected the resistance of the microbial communities to the disinfectant. With further increases in concentration, to >4 mg/L residual chlorine, no significant difference was observed in the disinfectant resistance of the microbial community.

title: Microbial abundance and community composition in biofilms on in pipe sensors in a drinking water distribution system.
abstract: Collecting biofilm samples from drinking water distribution systems (DWDSs) is challenging due to limited access to the pipes during regular operations. We report here the analysis of microbial communities in biofilm and water samples collected from sensors installed in a DWDS where monochloramine is used as a residual disinfectant. A total of 52 biofilm samples and 14 bulk water samples were collected from 17 pipe sections representing different water ages. Prokaryotic genome copies (bacterial and archaeal 16S rRNA genes, Mycobacterium spp. ammonia oxidizing bacteria (AOB) and cyanobacteria) were quantified with droplet digital PCR, which revealed the abundance of these genes in both biofilm and water samples. Prokaryotic 16S rRNA gene sequencing analysis was carried out for a subset of the samples (12 samples from four sites) Mycobacterium and AOB species were dominant in the DWDS sections with low water age and sufficient residual monochloramine, whereas Nitrospira species (nitrite oxidizing bacteria) dominated in the sections with higher water age and depleted monochloramine level, suggesting the occurrence of nitrification in the studied DWDS. The present study provides novel information on the abundance and identity of prokaryotes in biofilms and water in a full scale operational DWDS.

title: Impact of disinfection on drinking water biofilm bacterial community.
abstract: Disinfectants are commonly applied to control the growth of microorganisms in drinking water distribution systems. However, the effect of disinfection on drinking water microbial community remains poorly understood. The present study investigated the impacts of different disinfectants (chlorine and chloramine) and dosages on biofilm bacterial community in bench scale pipe section reactors. Illumina MiSeq sequencing illustrated that disinfection strategy could affect both bacterial diversity and community structure of drinking water biofilm. Proteobacteria tended to predominate in chloraminated drinking water biofilms, while Firmicutes in chlorinated and unchlorinated biofilms. The major proteobacterial groups were influenced by both disinfectant type and dosage. In addition, chloramination had a more profound impact on bacterial community than chlorination.

title: Source Community and Assembly Processes Affect the Efficiency of Microbial Microcystin Degradation on Drinking Water Filtration Membranes
abstract: Microbial biofilms in gravity driven membrane (GDM) filtration systems can efficiently degrade the cyanotoxin microcystin (MC) but it is unclear if this function depends on the presence of MC producing cyanobacteria in the source water habitat. We assessed the removal of MC from added Microcystis aeruginosa biomass in GDMs fed with water from a lake with regular blooms of toxic cyanobacteria (ExpL) or from a stream without such background (ExpS) While initial MC removal was exclusively due to abiotic processes, significantly higher biological MC removal was observed in ExpL. By contrast, there was no difference in MC degradation capacity between lake and stream bacteria in separately conducted liquid enrichments on pure MC. Co occurrence network analysis revealed a pronounced modularity of the biofilm communities, with a clear hierarchic distinction according to feed water origin and treatment type. Genotypes in the network modules associated with ExpS had significantly more links to each other, indicating that these biofilms had assembled from a more coherent source community. In turn, signals for stochastic community assembly were stronger in ExpL biofilms. We propose that the less "tightly knit" ExpL biofilm assemblages allowed for the better establishment of facultatively MC degrading bacteria, and thus for higher overall functional efficiency.

title: Effect of biofilm on cast iron pipe corrosion in drinking water distribution system: Corrosion scales characterization and microbial community structure investigation
abstract: Effect of biofilm on corrosion scales of cast iron pipe was studied with the biofilm community structure investigated by PCR DGGE to give an explanation to MIC from the viewpoint of microbial phase. Corrosion scales were identified with XRD and XPS. It was demonstrated that biofilm can greatly affect element composition and crystalline phase of corrosion scales. Biofilm can accelerate corrosion in 7 d, but inhibit corrosion after 7 d, which was due to iron bacteria and iron reducing bacteria (IRB) respectively. DGGE fingerprinting gave a well explanation to this transition, which might be contributed to the change of biofilm microbial diversity.