title: Changes in bacterial composition of biofilm in a metropolitan drinking water distribution system.
abstract: OBJECTIVE
  This study examined the development of bacterial biofilms within a metropolitan distribution system. The distribution system is fed with different source water (i.e. groundwater, GW and surface water, SW) and undergoes different treatment processes in separate facilities.
  
  
  RESULTS
  The biofilm community was characterized using 16S rRNA gene clone libraries and functional potential analysis, generated from total DNA extracted from coupons in biofilm annular reactors fed with onsite drinking water for up to 18 months. Differences in the bacterial community structure were observed between GW and SW. Representatives that explained the dissimilarity were associated with the classes Betaproteobacteria, Alphaproteobacteria, Actinobacteria, Gammaproteobacteria and Firmicutes. After 9 months the biofilm bacterial community from both GW and SW were dominated by Mycobacterium species. The distribution of the dominant operational taxonomic unit (OTU) (Mycobacterium) positively correlated with the drinking water distribution system (DWDS) temperature.
  
  
  CONCLUSIONS
  In this study, the biofilm community structure observed between GW and SW were dissimilar, while communities from different locations receiving SW did not show significant differences. The results suggest that source water and/or the water quality shaped by their respective treatment processes may play an important role in shaping the bacterial communities in the distribution system. In addition, several bacterial groups were present in all samples, suggesting that they are an integral part of the core microbiota of this DWDS.
  
  
  CONCLUSIONS
  These results provide an ecological insight into biofilm bacterial structure in chlorine-treated drinking water influenced by different water sources and their respective treatment processes.
authors.affiliation: United States Environmental Protection Agency, Cincinnati, OH, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Revetta
authors.affiliation: United States Environmental Protection Agency, Cincinnati, OH, USA.
authors.forename: V
authors.initials: V
authors.lastname: Gomez-Alvarez
authors.affiliation: ORISE, United States Environmental Protection Agency, Cincinnati, OH, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Gerke
authors.affiliation: United States Environmental Protection Agency, Cincinnati, OH, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Santo Domingo
authors.affiliation: United States Environmental Protection Agency, Cincinnati, OH, USA.
authors.forename: N J
authors.initials: NJ
authors.lastname: Ashbolt
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D044822:Biodiversity; D018441:Biofilms; D002713:Chlorine / Q000032:analysis; D060766:Drinking Water / Q000032:analysis / Q000382:microbiology*; D060587:Groundwater / Q000032:analysis / Q000382:microbiology; D018508:Water Purification; D060753:Water Quality; D014881:Water Supply / Q000592:standards
chemical_list: D060766:Drinking Water; D002713:Chlorine
keywords: biofilm; drinking water; drinking water distribution system; groundwater; microbial structure; surface water