The gastro-intestinal tract of mammals is colonised by trillions of bacteria after birth.

This community, or gut microbiota, performs numerous beneficial functions for the host, including energy extraction and immune regulation. Studies on the composition of the mammalian gut microbiota has been limited to captive or laboratory-reared terrestrial mammals and knowledge of this community in mammals from wild or marine environments is relatively unknown.

Tiffanie Nelson of the University of NSW is researching this gap with a comparative study of wild marine mammal hosts, the southern elephant, Mirounga Leonina, and the leopard seal, Hydrurga Leptonyx. Multiple molecular methods were used to characterise this community including next-generation sequencing. The gut microbiota of these seals was found to be a stable community in adulthood, distinct within each host species. A ‘core’ gut microbiota within all species of seals sampled, including three species from the Arctic, was identified and suggested to have co-evolved with these hosts over millions of years.

Dissimilarities in the gut microbiota between hosts were suggested to be a result of different dietary items influenced by the species, age and sex of the host. Dietary influences and antibiotic use were strong enough to exert an almost completely altered microbiota of captive compared with wild leopard seals. Exposure from the environment was found to be minimal, yet the potential for bacteria and genes to be transferred from human sewage in Antarctica was identified.

Composition of the gut microbiota in wild mammals is a result of interplay between evolutionary and dietary influences which may be a result of the functional capacity of bacteria in the gut. This research has implications for the future health of these hosts and provides insight into the gut microbiota of wild and marine mammals.

Read more in the Sydney Morning Herald November 2011 feature.


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