Methane matters: From blue tinged moos, to boozy roos, and for the health of humans too

Abstract Text: Methane production is a typical occurrence within the digestive tracts of warm blooded animals, including humans. Methanogens and methane emissions however, means something different to each host. Methane emissions from ruminant livestock has been a major focus of research over the last decade because of the attribution of ~10-20% of the annual anthropogenic methane output to these animals. This has led in part to methane emission measurements for a broad range of animal species and breeds, including Australia’s native herbivores, to identify “low emitters”; and resulted in comparative studies to define how the gut microbiota in these animals might account for the differences. The presence of methanogens within the human gut has long been recognised via a combination of breath methane measurements and microbiota surveys, and linked to a range of functional gastrointestinal disorders and non-communicable diseases. Historically much of the focus has been directed to the numerically most predominant species, principally assigned to the genus Methanobrevibacter, which are canonically involved with the conversion of gaseous substrates (CO₂ and H₂) arising from bacterial fermentation. However, recent studies by our group and others have revealed that perhaps, the heterotrophic methanogens (i.e. those capable of using small organic molecules such as alcohols and methylated amines) warrant closer attention, if “methane matters” in animals and man are to better managed. Here, we provide a brief overview of recent research on these heterotrophic archaea, with a specific focus on the genus Methanosphaera, which so far has been found only in the gastrointestinal tracts of animals, by using specific examples of our own and others recently published research with livestock, Australian macropodids (kangaroos and wallabies) and human clinical and nutritional studies. We propose this specific guild of methanogenic archaea not only warrants further attention, but provides new opportunities for the better management of the “animal-methane” axis.

Keywords: methane and methanogens, gut function, human health and animal productivity