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Appl. Environ. Microbiol. doi:10.1128/AEM.01221-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Occurrence of bifidobacteria in feces and environmental waters

Department of Environmental Engineering, University of Cincinnati, Cincinnati OH, 45220; U. S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 Martin Luther King Drive, MS-387, Cincinnati OH

^* To whom correspondence should be addressed. Email: santodomingo.jorge{at}epa.gov.

	Abstract

Bifidobacteria have been recommended as potential indicators of human fecal pollution in surface waters even though very little is known about their presence in non-human fecal sources. The objective of this research was to shed light on the occurrence and molecular diversity of this fecal indicator group in different animals and environmental waters. Genus- and specific-specific 16S rRNA gene PCR assays were employed to study the presence of bifidobacteria among 269 fecal DNA extracts from 32 different animals. Twelve samples from three wastewater treatment plants and 34 water samples from two fecally impacted watersheds were also tested. The species-specific assays showed that B. adolescentis, B. bifidum, B. dentium, and B. catenulatum had the broadest host-distribution (11.9% to 17.4%), while B. breve, B. infantis and B. longum were detected in less than 3% of all fecal samples. Phylogenetic analysis of 356 bifidobacterial clones obtained from different animal feces showed that approximately 67% of all the sequences clustered with cultured bifidobacteria, while the rest formed a supercluster with low sequence identity (i.e., <94%) to previously described Bifidobacterium spp. The B. pseudolongum subcluster (>97% similarity) contained 53 fecal sequences from seven different animal hosts, suggesting the cosmopolitan distribution of members of this clade. In contrast, two clades containing B. thermophilum and B. boum clustered exclusively with 37 and 18 pig fecal clones, respectively, suggesting host-specificity. Using genus-specific assays, bifidobacteria were detected in only three of the surface water DNA extracts, although other fecal anaerobic bacteria were detected in these waters. Overall, the results suggest that the use of bifidobacterial species as potential markers to monitor human fecal pollution in natural waters may be questionable.