Abstract
AbstractTrabulsiella guamensisis a non-pathogenic enterobacterium that was isolated from a vacuum cleaner on the island of Guam. It has one H2-oxidizing Hyd-2-type hydrogenase (Hyd), and encodes a H2-evolving Hyd that is most similar to the uncharacterizedEscherichia coliformate hydrogenlyase (FHL-2Ec) complex. The FHL-2Tgcomplex is predicted to have 5 membrane-integral and between 4-5 cytoplasmic subunits. We could show that FHL-2Tgcomplex catalyses the disproportionation of formate to CO2and H2. FHL-2Tghas an activity similar to theE. coliFHL-1Eccomplex in H2-evolution from formate, but the complex appears more labile upon cell lysis. Cloning of the entire 13 kbp FHL-2Tgoperon in the heterologousE. colihost has now enabled us to prove FHL-2Tgactivity unambiguously and allowed us to characterize the FHL-2Tgcomplex biochemically. Although the formate dehydrogenase (FdhH) genefdhFis not encoded in the operon, the FdhH is part of the complex and FHL-2Tgactivity was dependent on the presence ofE. coliFdhH. Also, in contrast toE. coli, T. guamensiscan ferment the alternative carbon source cellobiose, and we further investigated the participation of both the H2-oxidizing Hyd-2Tgand the H2-forming FHL-2Tgunder these conditions.ImportanceBiological H2-production presents an attractive alternative for fossil fuels. But in order to compete with conventional H2-production methods, the process requires our understanding on the molecular level. FHL complexes are efficient H2-producers and the prototype FHL-1Eccomplex inE. coliis well studied. This paper presents the first biochemical characterisation of an FHL-2-type complex. The data presented here will enable us to solve the long-standing mystery of the FHL-2Eccomplex, allow a first biochemical characterisation ofT. guamensis’s fermentative metabolism and establish this enterobacterium as model organism for FHL-dependent energy conservation.
Publisher
Cold Spring Harbor Laboratory