Quantitative lipid biomarker detection of unculturable microbes and chlorine exposure in water distribution system biofilms

Biofilms in the drinking water distribution system can protect pathogens fr om disinfection and provide the inocula for periodic infestations. Assessin g these biofilms can be difficult, as the plate counts of pelagic bacteria may bear little relationship to the biofilm load. Culturing the water at th e outlet most often does not reflect the biofilm composition. Herein we sho w that analysis of polar lipid fatty acids recovered from biofilms on devic es possessing a large surface area provides quantitative analysis of the Vi able biomass, community composition, and nutritional status that is indepen dent of the recovery and culturability. Analysis of the polar lipid fatty a cids indicated the biofilm contained a stressed and predominantly Gram-nega tive bacterial community. The composition was not significantly different w hether collected in the summer or winter. Oxirane (epoxide) fatty acids wer e detected in the polar lipids of the biofilm, indicating exposure to chlor ine and loss of viability within the biofilm. Tests with monocultures of Es cherichia coli and Sphingomonas paucimobilis exposed to chlorine resulted i n oxirane fatty acid generation and rendered them nonculturable. (C) 2000 E lsevier Science Ltd. All rights reserved.