Ecological characterisation of the colonic microbiota in arctic and sub-arctic seals.

Dominant colonic bacteria in wild hooded (n = 9), harbour (n = 1) and grey (n = 1) seals were identified using 16S rRNA gene clone libraries (313 clones), revealing 52.7% Bacteroidetes, 41.5% Firmicutes, 4.5% Proteobacteria and 1.0% Fusobacteria. Thirty (77%) of the 39 phylotypes identified were novel, showing <97% sequence similarity to their nearest cultivated relatives. Mean colonic bacterial cell density, determined by real-time PCR, was high (12.8 log(10) cells/g wet wt) for the hooded seals, while the number of methanogenic Archea was low (4.0 log(10) cells/g wet wt). The level of ampicillin (amp(r)) and tetracycline-resistant (tet(r)) isolates was investigated by cultivation. Aerobic amp(r) isolates were only detected in colon contents from four hooded seals, whereas aerobic tet(r) isolates were found in seven of the nine hooded seals. These data provide novel insight to the gut microbiota of Arctic and sub-Arctic seals living in the wild.