Dissection of the Hydrogen Metabolism of the Enterobacterium Trabulsiella guamensis: Identification of a Formate-Dependent and Essential Formate Hydrogenlyase Complex Exhibiting Phylogenetic Similarity to Complex I.

ABSTRACT: Trabulsiella guamensis is a nonpathogenic 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 an H₂-evolving Hyd that is most similar to the uncharacterized Escherichia coli formate hydrogenlyase (FHL-2 _Ec ) complex. The T. guamensis FHL-2 (FHL-2 _Tg ) complex is predicted to have 5 membrane-integral and between 4 and 5 cytoplasmic subunits. We showed that the FHL-2 _Tg complex catalyzes the disproportionation of formate to CO₂ and H₂ FHL-2 _Tg has activity similar to that of the E. coli FHL-1 _Ec complex in H₂ evolution from formate, but the complex appears to be more labile upon cell lysis. Cloning of the entire 13-kbp FHL-2 _Tg operon in the heterologous E. coli host has now enabled us to unambiguously prove FHL-2 _Tg activity, and it allowed us to characterize the FHL-2 _Tg complex biochemically. Although the formate dehydrogenase (FdhH) gene fdhF is not contained in the operon, the FdhH is part of the complex, and FHL-2 _Tg activity was dependent on the presence of E. coli FdhH. Also, in contrast to E. coli, T. guamensis can ferment the alternative carbon source cellobiose, and we further investigated the participation of both the H₂-oxidizing Hyd-2 _Tg and the H₂-forming FHL-2 _Tg under these conditions.IMPORTANCE Biological H₂ production presents an attractive alternative for fossil fuels. However, in order to compete with conventional H₂ production methods, the process requires our understanding on a molecular level. FHL complexes are efficient H₂ producers, and the prototype FHL-1 _Ec complex in E. coli is well studied. This paper presents the first biochemical characterization of an FHL-2-type complex. The data presented here will enable us to solve the long-standing mystery of the FHL-2 _Ec complex, allow a first biochemical characterization of T. guamensis's fermentative metabolism, and establish this enterobacterium as a model organism for FHL-dependent energy conservation.

SUBMITTER: Lindenstrauß U 

PROVIDER: S-EPMC6531613 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature