Water quality monitoring techniques that target microorganisms in the order Bacteroidales are potential alternatives to conventional
methods for detection of fecal indicator bacteria. Bacteroidales and members of the genus Bacteroides have been the focus
of microbial source tracking (MST) investigations for discriminating sources of fecal pollution (e.g., human or cattle feces) in
environmental waters. For accurate source apportionment to occur, one needs to understand both the abundance of Bacteroides
in host feces and the survival of these host-associated microbial markers after deposition in the environment. Studies were undertaken
to evaluate the abundance, persistence, and potential for growth of Bacteroidales originating from poultry litter under
oxic and anoxic environmental conditions. Bacteroidales abundance, as determined by quantitative PCR (qPCR) with GenBac
primers and probe, increased 2 to 5 log gene copies ml1 and 2 log gene copies g litter1 under most conditions during incubation
of poultry litter in a variety of laboratory microcosm and field mesocosm studies. DNA sequencing of the Bacteroidales organisms
in the litter identified taxa with sequences corresponding exactly to the GenBac primer and probe sequences and that
were closely related to Bacteroides uniformis, B. ovatus, and B. vulgatus. These results suggest that MST studies using qPCR
methods targeting Bacteroidales in watersheds that are affected by poultry litter should be interpreted cautiously. Growth of
Bacteroidales originating from poultry litter in environmental waters may occur while Bacteroidales growth from other fecal
sources declines, thus confounding the interpretation of MST results.