Formate Energizes Microbes

Some species of single-celled organisms called archaea can survive with only formate providing their energy needs, reports an international group led by Jung-Hyun Lee and Sung Gyun Kang of the Korea Ocean Research & Development Institute (Nature 2010, 467, 352). The work builds on a finding two years ago by Jan Dolfing and coworkers at Wageningen University, in the Netherlands, that communities of bacteria and archaea, each of which performed a different function, could also live off formate. Kim and colleagues determined that certain species of the Thermococcus genus of archaea survive by converting formate (HCOO_–) to CO₂ and H ₂ and then coupling that reaction to adenosine triphosphate (ATP) synthesis. By studying gene expression in the microbes, the researchers propose that a formate dehydrogenase enzyme converts HCOO_– to CO ₂ and H⁺. A hydrogenase then turns the H₊ into H while transporting additional H₊ out of the cell. An “antiporter” protein brings H⁺ back into the cell while pushing out Na₊. Finally, an ATP synthase uses the sodium gradient to drive ATP synthesis from adenosine diphosphate (ADP) and HPO_{4 2–}.