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Changes in Biofilm Community Structure Associated with Monochloramine-treated Drinking Water Biofilms
Citation:
REVETTA, R. P., V. GOMEZALVAREZ, J. W. SANTO-DOMINGO, T. L. GERKE, AND N. ASHBOLT. Changes in Biofilm Community Structure Associated with Monochloramine-treated Drinking Water Biofilms. Presented at American Society for Microbiology General Meeting, San Francisco, CA, June 16 - 20, 2012.
Impact/Purpose:
To inform the public.
Description:
Monochloramine is increasingly used as a drinking water disinfectant because it forms lower levels of traditional disinfectant by-products compared to free-chlorine disinfection treatment. The use of monochloramine has been shown to increase ammonia-oxidizing bacteria and the presence of mycobacteria, but little is known about how it affects the microbial community composition within drinking water systems. In this study, we used sequencing of 16S rRNA genes from total DNA biofilm extracts to examine the bacterial succession within a monochloramine-treated drinking water experimental pipe-loop system. Samples were collected over a period of seven months from in-line and off-line biofilm capturing devices using borosilicate glass beads or polycarbonate coupons from annular reactors. Approximately 90% of the total diversity in all samples combined was associated with the phyla Actinobacteria, Bacteroidetes and Proteobacteria. No significant difference was observed between in-line and off-line capturing devices or coupon surface used. However, differences in community structure were evident when samples were grouped by month, suggesting that all communities underwent a succession over time. Early stages of biofilm formation (up to one month) were dominated by Serratia (30%), Cloacibacterium (22%), Diaphorobacter (17%), and Acinetobacter (5%), while Mycobacterium-like phylotypes were the most predominant populations (>29%) in the subsequent months (two months to seven months). Nitrifying bacteria closely related to Nitrospira moscoviensis and Nitrosospira multiformis were detected after three months. The Mycobacterium-like sequences identified were closely related to M. gordonae, M. mucogenicum, and M. abscessus; nontuberculous mycobacteria often isolated from potable water supplies and in some cases implicated in outbreaks targeting individuals with predisposing conditions. These results provide an ecological insight into biofilm succession of microbial populations in monochloramine-treated drinking water. A more comprehensive understanding of the microbial ecology of drinking water systems relative to disinfection regime will enable more effective management of water quality in these engineered systems, and subsequently help to safeguard human health.
