THIOREDOXIN BASED REDOX CONTROL OF METABOLISM IN METHANE FORMING ARCHAEA: EVOLUTIONARY AND METABOLIC IMPLICATIONS

Methanogenic archaea or methanogens are a group of strictly anaerobic microorganisms that appeared on Earth about 3.5 billion years ago. They produce methane from simple compounds such as hydrogen+carbon dioxide, carbon monoxide, formate, methanol, methylamines, methyl sulfides and acetate in a variety of anaerobic niches of nature. Methane is a valuable fuel as well as a potent green house gas. We are investigating the mechanisms that methanogens use to cope with redox shocks. From a proteomics investigation we have found that thioredoxin, a small redox protein that has been known to control a spectrum of processes in eukaryotes and bacteria by changing the thiol redox status (SH/S-S) of selected proteins, likely allows methanogens to live through variations in the availability of energy supply (low potential electrons) or oxygen exposure. Our data shows that all aspects of cellular processes, from methanogenesis to information processing and prevention of phage infection, are covered by this control/defense system. This capability not only fits the needs of the methanogens on today’s Earth but also was likely important to them on early Earth and helped ancient methanogens to survive through the changes brought about by the arrival of oxygen in the atmosphere 2.5 billion years ago. These possibilities indicate that complex cellular regulatory processes developed early in the evolution. On the applied side, the findings have implications in the biological production of natural gas, feed utilization in ruminants, anaerobic waste treatment, and mitigation of green house gas emission.