The dormant majority

Our world is inhabited by a tremendous abundance and diversity of microorganisms. Even extreme environments, from Antarctica to Yellowstone, harbour rich microbial communities. This reflects that microbes are highly metabolically versatile: they can thrive even in environments deprived of the organic carbon and oxygen required for animal life. What’s more, microbes are capable of resisting environmental stresses and reducing energy expenditure by entering dormant states analogous to seeds.

Our research explores how the dormant microbial majority sustain their energy needs. We use this knowledge to address fundamental questions about community assembly, primary production, and biogeochemical cycling. Along the way, this research has taken us to plenty of interesting places: Antarctic soils, volcanic craters, and oceanic sediments to name a few.

Current projects

1. Atmospheric trace gases as reserve energy sources for dormant soil bacteria (ARC DECRA Fellowship, 2017 – 2019)
2. Primary production and microbial community composition in global desert ecosystems (Antarctic Australian Division Grant, 2017 – 2020)
3. Microbial community structure and function in marine sediments (ARC Discovery Project Grant, 2018 – 2021)
4. Quantification of turnover of soil microbial communities across multiple spatial scales (Holsworth Foundation, 2018 – 2019)
5. Tri-trophic interactions in ecosystem multifunctionality (Holsworth Foundation, 2017 – 2018; led by Prof Melodie McGeoch)

We are also bringing our expertise in the areas of bioenergetics and microbiology to address key ecological and evolutionary questions developed by other members of Monash University’s School of Biological Sciences and Centre for Geometric Biology.

Previous findings

Our most notable finding is that atmospheric trace gases sustain maintenance of microbial communities. Diverse soil bacteria are supported by hydrogen and carbon monoxide, including Actinobacteria (PNAS 2014a, PNAS 2014b), Acidobacteria (PNAS 2015), Verrucomicrobia (ISME 2017b), Chloroflexi (ISME J 2019), and two candidate phyla (Nature 2017). Such atmospheric energy sources support primary production in oligotrophic ecosystems, providing an alternative basis for ecosystem function to solar or geological energy (Nature 2017).

Figure: Microbial community structure of three desert soils from Eastern Antarctica. We showed these diverse communities have a low capacity for photosynthesis and are instead primarily supported by atmospheric trace gases as energy and carbon sources (Nature 2017).

Our work has also emphasised the importance of interactions between fermentative and respiratory bacteria in the function of diverse sediments (Nature Geoscience 2017, ISME 2018, Nature Microbiol 2019a) and the process of eukaryogenesis (Nature Microbiol 2019b).

Research team

Staff: Dr Eleonora Chiri (Postdoctoral Fellow), Guy Shelley (research assistant)
Students: Sean Bay (PhD), Ya-Jou Chen (PhD), Bob Leung (PhD), Sarah Reeve (PhD)
Collaborators: A/Prof Belinda Ferrari, Prof Philip Hugenholtz, Prof Melodie McGeoch, Prof Steven Chown, Prof Paul Sunnucks, Dr Osnat Gillor, Dr Xiyang Dong