The vertebrate animal gut in context ? microbiomes, metagenomes and methane

Abstract

The microbial world colonises the gastrointestinal tracts of vertebrates soon after birth or hatching. These animal-microbe relationships have been described as competitive, cooperative or combinatorial, and all provide a variety of functional and metabolic capabilities that are relevant to host animal nutrition, health and well-being. The evolutionary adaptations of Australia?s marsupial herbivores have been relatively well characterised and favour both the cooperative and combinatorial animal-microbe models. Kangaroos and wallabies possess the cooperative model: the foregut functions as an obligate combustion chamber for a microbiome specialised in the release of nutrients from plant biomass, and which precedes a region of acid and pepsinogen secretions by the host. The common ringtail possum and wombats are examples of Australian herbivores with specialised caecal and colonic obligate combustion chambers, respectively. As such, these animals typify the combination model of animal-microbe association: the stomach and its associated digestive processes precede the obligate combustion chamber and its resident microbiome that coordinates the enzymatic hydrolysis and fermentation of plant biomass.