Factors Influencing the Gut Microbiota of Antarctic Seals

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Copyright: Nelson, Tiffanie
A mammal’s gastro-intestinal tract houses trillions of bacteria, known as the gut microbiota, which is first acquired during birth. This community provides a number of beneficial functions to the host, including breakdown of food and creation of energy, immunity regulation and cellular development. To date, studies on the mammalian gut microbiota have focused primarily on captive or laboratory-reared terrestrial mammals and there have been a limited number of studies on mammals living under natural conditions or from marine environments. This thesis aimed to address this knowledge gap through a study on the gut microbiota of the southern elephant seal, Mirounga leonina, and the leopard seal, Hydrurga leptonyx, inhabiting Antarctica. The study was designed to understand how time, diet, phylogeny, age, sex, maternal relationship, sewage contamination and captivity influence composition. DNA extracted from faecal samples was analysed via multiple molecular methods to identify an individual’s gut microbiota. The community was dominated by four phyla: Firmicutes, Fusobacteria, Proteobacteria and Bacteroidetes and was identified as stable over a period of months. Diet-driven differences were noted between individuals as a result of species, captivity, sex and age. Specifically, nutrient composition of the diet and bacteria associated with the diet were identified as strong influences on the gut microbiota. Length of the gut, social interactions and antibiotic use were also identified as contributing factors. Despite the observed differences in the gut microbiota between hosts, a ‘core’ microbiota was identified between Antarctic seal species and also between three related species of Arctic seals. This is suggested to be a result of co-evolution which is maintained over generations via transfer from mother to pup. Bacterial isolates possessing virulence factors and resistance to antimicrobial agents were also identified in the gut of these hosts suggesting they may be vulnerable to sewage contamination containing novel bacteria. This research provides a baseline for future work regarding bacterial associations in these hosts. It identifies the complex community inhabiting the gut of mammals and the factors which contribute to its composition. Additionally, it indicates the differences that exist between mammals living in captivity and under natural conditions and has implications for the future health of these hosts.
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Nelson, Tiffanie
Rogers, Tracey
Brown, Mark
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PhD Doctorate
UNSW Faculty
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