Muruleedhara Byappanahalli Ashley Spoljaric Katarzyna Przybyla-Kelly Dawn A. Shively Meredith Nevers Richard L. Whitman 2014 <p><i>Bacteroides</i> is assumed to be restricted to the alimentary canal of animals and humans and is considered to be non-viable in ambient environments. We hypothesized that <i>Bacteroides</i> could persist and replicate within beach-stranded <i>Cladophora glomerata</i> mats in southern Lake Michigan, USA. Mean <i>Bacteroides</i> concentration (per GenBac3 Taqman quantitative PCR assay) during summer 2012 at Jeorse Park Beach was 5.2 log calibrator cell equivalents (CCE) g^-1 dry weight (dw), ranging from 3.7 to 6.7. We monitored a single beach-stranded mat for 3 wk; bacterial concentrations increased by 1.6 log CCE g^-1 dw and correlated significantly with ambient temperature (p = 0.003). Clonal growth was evident, as observed by &gt;99% nucleotide sequence similarity among clones. In<i> in vitro</i> studies, <i>Bacteroides</i> concentrations increased by 5.5 log CCE g^-1 after 7 d (27&deg;C) in fresh <i>Cladophora</i> collected from rocks. Partial sequencing of the 16S rRNA gene of 36 clones from the incubation experiment showed highly similar genotypes (&ge;97% sequence overlap). The closest enteric<i> Bacteroides</i> spp. from the National Center for Biotechnology Information database were only 87 to 91% similar. Genomic similarity, clonality, growth, and persistence collectively suggest that putative, free-living <i>Bacteroides</i> inhabit <i>Cladophora</i> mats of southern Lake Michigan. These findings may have important biological, medical, regulatory, microbial source tracking, and public health implications.</p> application/pdf 10.3354/ame01688 en Inter-Research Evidence for free-living Bacteroides in Cladophora along the shores of the Great Lakes article