Microbial Characterization and Related Metabolic Functions of Biofilms from a Real Full-Scale Drinking Water Distribution System (Dwds) Subjected to Chlorination

Biofilms, which account for more than 95% of the total biomass in drinking water distribution system, constitute an ecosystem that can influence the 'aesthetic' quality of water, altering taste, color or smell, and also the microbiological quality of water. In this work, the study of the microbiome of biofilms located in real scale drinking water distribution system from eastern Spain has been carried out using amplicon-based metagenomics. Forty-one biofilm samples were processed and sequenced to obtain both the bacterial and eukaryotic microbiome. Determination of the active biomass as well as functional prediction of the bacterial microbiome of biofilms were also carried out. Moreover, different statistical analysis were performed to determine which bacteria characterize differences among pipe materials, the microbial community differences between pipe materials or the relationships between bacteria and the metabolic pathways. At genus level samples were found to be very heterogeneous. The most abundant genera were Desulfovibrio, Ralstonia, Bradyrhizobium, Methylocystis and Bacillus. The presence of potentially pathogenic bacteria, such as Helicobacter, Pseudomonas or Legionella, and bacteria with possible involvement in corrosion processes such as Sulfuricella, Hyphomicrobium or Methylobacterium were found. Regarding protozoa, Opisthokonta and Archaeplastida were the most abundant groups over biofilm samples. Potential pathogenic eukaryotes such as Acanthamoeba, Naegleria or Blastocystis were detected among the samples. This study did not find a direct relationship between the microbiota composition and pipes’ materials where these biofilms were found. It seems that the presence of high concentration of free chlorine in bulk water was not sufficient to avoid the presence of undesirable bacteria and protozoa in biofilms which showed to contain a high concentration of active biomass