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.