Methane-oxidising bacteria have a second energy source

An international research team has discovered that methane-oxidising bacteria are more flexible and resilient than previously thought, in a breakthrough that could have major implications for greenhouse gas mitigation.

Bacteria that oxidise methane (methanotrophs) are globally important in capturing methane before it enters the atmosphere. Some industrial companies use methanotrophs to convert methane gas emissions into useful products, eg, liquid fuels and protein feeds.

Curiously, though, methanotrophs can survive in environments when methane or oxygen are no longer available — particularly soil ecosystems. Monash University’s Dr Chris Greening, co-lead author on the new study, wanted to find out how this was possible.

Dr Greening and his collaborators isolated and characterised a methanotroph from a New Zealand volcanic field. They found that the strain could grow on methane or hydrogen separately, but performed best when both gases were available.

Published in The ISME Journal, the study reveals that the methanotrophs were actually mixotrophs — organisms that can use a mix of different sources of energy and carbon. Specifically, they can consume hydrogen gas as well as methane to enhance their growth and survival.

“The findings of this research explain why methanotrophs are abundant in soil ecosystems,” said Dr Greening, who noted that methane is a challenging energy source to assimilate.

“By being able to use hydrogen as well, methanotrophs can grow better in a range of conditions,” he said.

So what does this mean for greenhouse gas mitigation? Well, industrial processes such as petroleum production and waste treatment release large amounts of methane, carbon dioxide and hydrogen into the atmosphere. If these methane-consuming methanotrophs are in fact able to grow on inorganic compounds such as hydrogen, said Dr Greening, it may be possible to convert a vast majority of these greenhouse gases into useful liquid fuels and feeds instead.

Image credit: ©stock.adobe.com/au/andreusK