Dear Biology Students, Postdocs, and Faculty,
Next week for our Faculty Seminar Series at 1:00 p.m. on Monday, December 22nd, we will have a talk by Dr. Jonathan Gropp of the Department of Earth and Planetary Science, University of California, Berkeley, CA, USA. Dr. Jonathan Gropp will present a talk titled “Decoding microbial methane production: from genes to ecosystems”.
Talk Abstract:
Methanogenic archaea (methanogens) have the unique capability to couple methane (CH4) production with growth and energy conservation, and they play a key role in the global carbon biogeochemical cycle. Despite this, significant gaps remain in our understanding of their physiology, metabolism, and ecology. This talk presents a platform for bridging this gap by using stable isotopes as probes to decode microbial methane production from the gene to the ecosystem level.
In my work, I study microbial methane metabolism using the stable isotopic ratios of carbon and hydrogen (13C/12C and 2H/1H) in methane, which are widely used to trace methanogenic activity in natural environments. We have recently found that isotopic signatures of methane produced in laboratory cultures are distinct from those in natural environments. We have proposed that growth under energy-limiting conditions increases enzyme reversibility, thereby inducing isotopic exchange and altering isotopic signatures. To test this “reversibility hypothesis,” we used a genetically tractable methanogenic strain modified via CRISPR-Cas9 to control the expression of methyl–coenzyme M reductase (MCR), a key enzyme in the pathway. Our results demonstrate that MCR down-regulation decreases growth rates and alters the isotopic signature of the methane, confirming that enzyme reversibility sets isotopic signatures under non-optimal growth conditions. We further found that temperature variations produce similar effects, indicating that enzyme reversibility is prevalent during methanogenic growth, especially under conditions found in natural environments. These findings demonstrate the utility of novel genome-editing techniques and stable-isotope probing as powerful tracers of biochemical processes in microbial metabolism and physiology.
Finally, I will discuss future directions for my work, using experimental and theoretical approaches, including, for example, developing novel metabolic and isotopic biomarkers to track nitrogen fixation by methanogens. Nitrogen fixation first emerged in methanogens, but their role in the nitrogen cycle remains unclear. I aim to elucidate this enigma, linking the carbon and nitrogen biogeochemical cycles. Such studies establish mechanistic frameworks to understand the fundamentals of microbial physiology and ecology, paving the way for targeted strategies to mitigate climate change and enhance renewable energy production.
Looking forward to seeing you!
Maya
