GLOBAL CHANGE THEME: GAS METABOLISM

Trace gas scavenging

Microorganisms control the composition of our atmosphere. They consume and produce various climate-relevant atmospheric trace gases through metabolic processes. For example, soil bacteria consume three quarters of the 1014 grams of hydrogen taken up from the atmosphere each year — they scavenge this gas using high-affinity metalloenzymes and use it as a reserve energy source in their dormant state. Other microorganisms regulate the levels of methane, carbon monoxide, and carbon dioxide in the atmosphere.

We have collected evidence that scavenging of atmospheric trace gases is widespread among microorganisms. We are now performing interdisciplinary studies to better understand the biochemical basis, physiological role, and ecological significance of trace gas scavenging and other gas-cycling processes. The knowledge is being used to help predict and mitigate greenhouse gas emissions.

Current projects

1. Atmospheric trace gases as reserve energy sources for dormant soil bacteria (ARC DECRA Fellowship, 2017 – 2019)
2. Hydrogen cycling in marine sediments and water columns (ARC Discovery Project Grant, 2018 – 2021)
3. Pathways of gas production and consumption in the human gastrointestinal tract
4. Biochemical basis of high-affinity hydrogen oxidation 
5. Hidden metabolic flexibility of methane-oxidising bacteria
(Marsden Project Grant, 2017 – 2019; led by Dr Carlo Carere)

Previous findings

We have shown that dormant soil microorganisms consume atmospheric trace gases as reserve energy sources (Nature 2017). In addition, we have resolved the organisms and enzymes responsible for the consumption of atmospheric hydrogen (PNAS 2014aPNAS 2014bPNAS 2015, AEM 2015). Moreover, we have shown hydrogen metabolism is ubiquitous across microbial taxa (ISME 2015SREP 2016) and is critical for ecosystems as diverse as coastal sediments (Nature Geo 2017), geothermal soils (ISME 2017b), and the human colon (Gut Microbes 2016).

hydrogenasediversity

Figure: Phylogenetic trees of hydrogenase protein sequences across microbial taxa. This demonstrates that the enzymes that mediate the oxidation and evolution of H2, are highly phylogenetically diverse, functionally versatile, and taxonomically widespread (ISME 2015).

Research team

Staff: Eleonora Chiri (Postdoctoral Fellow), Tent Jirapanjawat (Research Assistant), Blair Ney (Research Assistant)
Students: Sean Bay (PhD), Ya-Jou Chen (PhD), Paul Cordero (PhD), Zahra Islam (PhD), Guy Shelley (Honours)
Collaborators: Dr Carlo Carere, A/Prof Perran Cook, Prof Gregory Cook, Prof Rex Gaskins, Dr Matthew Stott, Dr Sergio Morales