Age-related differences revealed in Australian fur seal Arctocephalus                 pusillus doriferus gut microbiota.
Molecular analysis of the dominant microbiota in Arctocephalus pusillus                 doriferus (Australian fur seals, Family Otariidae) at different ages was undertaken                 using fluorescent in situ hybridisation (FISH) and then 16S rRNA pyrosequencing.                 Comparative phylogenetic assessment of the gut microbiota in faecal samples (scats)                 from 2 month-old (2 mo), 9 month-old (9 mo) and 2 year old adult fur seals using                 FISH, showed the dominant bacterial phyla included the Firmicutes, Bacteroidetes,                 Actinobacteria and Proteobacteria with significant quantitative differences in the                 predominant bacterial phyla especially between 2 mo pups and 9 mo pups at the time                 of weaning. The phylum Firmicutes revealed a relative abundance of 21.85% in two mo                 seal pups, 56.6% in 9 mo seal pups and 71.85% in adult seals. Bacterial                 representatives belonging to the phylum Bacteroidetes ranged from 2-4% in the fur                 seal age-groups, respectively. Actinobacteria were present with 1.44%, 4.28% and                 1.75%, respectively using the combined ATO 281 and Bif 164 probes. Class                 Gammaproteobacteria (phylum Proteobacteria) observed using the EC 1531 probe                 accounted for 1.82% in the 2 mo pups but < 1% of bacterial numbers for the other                 fur seal age groups. The relative abundance and composition of these major phyla in                 2, 6 and 9 month-old pups was further examined using 16 S rRNA pyrosequencing. A                 total of 12,163 partial 16S rRNA gene sequences were amplified from the 2 mo pups                 compared with 26,234 sequences from samples taken from 6 mo pups and 37,460 gene                 sequences from the 9 mo pups. Significant differences in the composition at all                 phylogenetic levels were observed in the bacterial phyla of Bacteroidetes,                 Actinobacteria, Proteobacteria, Verrucomicrobia and Fusobacteria at all ages and                 between classes and order within Firmicutes. The abundance of the predominant                 bacterial phyla differ between Australian fur seals at different ages of development                 and even when compared to the Australian Sea lion and other Arctic and sub-arctic                 seals.