Despite eating the same sort of grassy diet that cows do, Australia’s grazing marsupials produce only a small fraction of the amount of methane gas. Researchers have now identified a bacterium, which they call WG-1, that they believe holds the key as to why one marsupial, the Tammar wallaby, produces about one-fifth the amount of methane per unit of digestible energy that livestock such as cows and sheep produce.

The metabolic properties of the bacterium suggest that it may be part of the reason why wallabies produce less methane than ruminants. In ruminants, carbon dioxide and hydrogen are common by-products of fermentation; these are converted by other microbes into methane. However, the new bacterium found in the wallaby gut instead produces succinate, acetate and formate, while also using carbon dioxide.

To study WG-1, Phillip Pope of CSIRO Livestock Industries in Australia and colleagues from the US and Germany used a novel approach called metagenomics, in which genome sequencing predicted the culture conditions necessary to isolate this microbe.

Mark Morrison, co-author of the Science paper, told environmentalresearchweb: ”A major challenge is that the percentage of microbes that can be readily grown in the lab represent only a small fraction of what exists in nature. So we extract DNA from all the microbes present in the natural sample, sequence that DNA, then start to characterize the structure and function of that real-world microbial community.”

Morrison believes that this approach can also be applied to analysis of the bacteria in the gut of ruminant livestock such as cows. “We know there are distant relatives of the wallaby bacterium (WG-1) in ruminant livestock, so our goal is to find ways to stimulate their numbers in the rumen, and achieve a similar effect,” he said.

Since carrying out the research at CSIRO, Pope is now working at the University of Life Sciences (UMB) in Norway, and is studying the gut bacteria of Norwegian reindeer to find out more about how biomass is degraded in their gut.

"Reindeer often have to get by on very little food and need to make the most of what they eat,” said Pope. “Their diet in winter mainly consists of arctic shrubs, which are not easily degradable. We therefore anticipate that reindeer gut bacteria have very efficient enzymes which convert biomass into energy and nutrients. We are now looking to identify bacteria and enzymes in the reindeer gut and for the first time we will have a unique opportunity to compare the microbiology of animals living in different environments and under very different conditions.”

Meanwhile, Morrison and his colleagues in Australia plan to use their knowledge and approaches to isolate bacteria distantly related to WG-1 from livestock. “Then, by using a combination of microbiological and molecular methods, we want to understand what we need to do to increase their numbers, and contribution, to rumen feed digestion and fermentation,” said Morrison.

He believes that using a combination of these microbiological approaches with research like that in the Science paper, along with animal breeding and nutrition, offers the greatest likelihood of further reducing methane emissions from livestock. “I don't think there is a singular reason - or microbe – that will solely provide the solution for reduced methane emissions from livestock,” he said. “Rather, it will be a combination of approaches used together that will produce the desired result.”