Seminars & Events

IGSB Seminar
""Carbon monoxide based metabolism, CO cycling in anaerobic microbial ecosystems, and the composition of early Earths atmosphere""

DATE: February 6, 2012 to February 6, 2012
TIME: 10:00 AM - 11:00 AM
SPEAKER: Albert Colman, Assistant Professor University of Chicago Geophysical Sciences Department
LOCATION: Building 240/Conference Room 1407, Argonne National Laboratory
HOST: Jack Gilbert

Description:
Carbon monoxide binds tightly to many hemes and other porphyrins, proving toxic to humans and microbes. Nevertheless, CO is an attractive fuel for anaerobic chemolithotrophy for those microbes not impaired by COs toxicity. CO can be oxidized to CO2 anaerobically through the water-gas-shift reaction by hydrogenogenic carboxydotrophs. CO can also be used by certain homoacetogens in the production of acetate and by certain methanogens in the production of methane, acetate, and formate.

CO is not only consumed by microbes, but a diverse range of evidence points towards biogenic production of CO. We present measurements of CO concentrations in dissolved and free phase gases in hot springs in Kamchatka, Russia, and Lassen Volcanic National Park, CA. These measurements implicate microbial CO production as a dominant source of CO in these anaerobic ecosystems. Biogenic CO production has important repercussions for the chemistry of the atmosphere and climate, especially on the ancient Earth.

There are few in situ measurements of dissolved CO in microbial mats and sediment pore waters. However, the concentration dependent biochemical and transcriptional responses of carboxydotrophs to CO offer strong evidence for the growth conditions to which these microbes have adapted. CooA is a CO-sensing transcriptional activator found in most anaerobic carboxydotrophs. We interpret the CO-binding properties of CooA in Carboxydothermus hydrogenoformans and Rhodospirillum rubrum as evidence for the ranges of environmental CO concentrations that are frequently encountered in anaerobic ecosystems.

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