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The Houtermans Medal was presented today to Nathan Yee, assistant professor at Rutgers. His medal talk, delivered in Session 16a, was titled “The Genetics and Geochemistry of Microbe-Selenium Interactions“.

It’s ever more beneficial for biogeochemists to be fluent in the genetics of  geochemistry. Yee is. Describing his work in Enterobacter and E. coli he outlined the discovery of genes involved in selenate reduction, including a novel selenate reductase.

Although selenate itself might not play a major role in global biogeochemical cycles, it may provide clues about evolution and Earth history. Selenate reduction occurs only under anaerobic conditions, but selenate is the oxidized form of  selenium, and is difficult to form without O2. With selenate scarce to nonexistent prior to the Great Oxidation Event, respiration by selenate reduction probably didn’t exist. Yee also points out that the selenate reductase enzyme – like many related reductases involved in anaerobic respiration – requires molybdenum, which also is widely available only in an aerobic world. By allowing molybdenum to become widely available the Great Oxidation Event may, ironically, have unlocked a number of new possible pathways for anaerobic respiration.

One wonders how anaerobic metabolism might have been affected after the GOE, such as during the Mesoproterozoic when sulfidic oceans may have limited molybdenum availability. Along with inhibiting primary productivity, the molybdenum scarcity may have had a negative impact on some anaerobic respiration pathways, potentially influencing rates of organic carbon recycing, or driving the evolution of replacement enzymes.  Geochemistry exerts its power over enzyme function, which in turn influences geochemistry. Uncovering these feedbacks make it increasingly apparent that we must appreciate both genes and geochemistry to make sense of either.

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