Mary Ann Bruns
Associate Professor, Soil Microbiology,Department of Crop & Soil Sciences
The Pennsylvania State University
Hydrogen probably has functioned for billions of years as a universal energy currency in an invisible "prokaryotic hydrogen economy." Globally, prokaryotes (i.e., bacteria and archaea) make up as much biomass as plants. Due to their enormous numbers (an estimated total of 4-6 x 10^30 prokaryotic cells on earth), the cumulative amount of gas transferred between hydrogen producers and consumers is massive. This overview highlights bacterial processes which generate hydrogen (photolysis, dark fermentation, carbon monoxide conversion, nitrogen fixation) and discusses how intercellular hydrogen transfers and other microbial interactions offer insights for developing a bioenergy economy on a larger scale.