Differences downunder: macropodids, methane and metagenomics.
The agricultural sector accounts for a large amount of Australia’s greenhouse gas emissions, and strategies that reduce the production and (or) release of methane from ruminant livestock has resurfaced as a viable research topic. While there has been a relatively intense focus on better understanding how rumen microbiology, nutrition and (or) animal genetics might be targeted and productively altered to reduce these emissions; less attention has been directed towards the comparative study of those native Australian herbivores thought to produce small amounts of methane during feed digestion. These animals include the Australian macropodids (kangaroos and wallabies), which have evolved to retain a foregut microbiota that effectively converts plant biomass into nutrients for the host animal; and appears to do so with much less methane emitted. Our research group in Brisbane has used metagenomics approaches with a view to characterize the foregut microbiota of the Tammar wallaby (Macropus eugenii). There is a reduced number of methanogenic archaea resident in the macropodid foregut compared to ruminants, but the species present appear to have some unique attributes relative to their counterparts from other environments. We have also used a combination of metagenomic data and cultivation-based methods to identify and isolate several “new” bacteria that support feed digestion and fermentation schemes consistent with a low methane emitting phenotype. The structure-function relationships inherent to these interesting gut microbiomes warrant further investigation.