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Evidence for a key role of cytochrome bo3 oxidase in respiratory energy metabolism of Gluconobacter oxydans

ABSTRACT: The obligatory aerobic acetic acid bacterium Gluconobacter oxydans oxidizes a variety of substrates in the periplasm by membrane-bound dehydrogenases, which transfer the reducing equivalents to ubiquinone. Two quinol oxidases, cytochrome bo3 and cytochrome bd, then catalyze transfer of the electrons from ubiquinol to molecular oxygen. In this study, mutants lacking either of these terminal oxidases were characterized. Deletion of the cydAB genes for cytochrome bd had no obvious influence on growth, whereas the lack of the cyoBACD genes for cytochrome bo3 severely reduced the growth rate and the cell yield. Using a respiration activity monitoring system and adjusting different levels of oxygen availability, hints for a low oxygen affinity of cytochrome bd oxidase were obtained, which were supported by measurements of oxygen consumption in a respirometer. The H+/O ratio of the M-NM-^TcyoBACD mutant with mannitol as substrate was 0.56 M-BM-1 0.11 and more than 50% lower than that of the reference strain (1.26 M-BM-1 0.06) and the delta-cydAB mutant (1.31 M-BM-1 0.16), indicating that cytochrome bo3 oxidase is the main component for proton extrusion via the respiratory chain. Plasmid-based overexpression of cyoBACD led to increased growth rates and growth yields, both in the wild type and the delta-cyoBACD mutant, suggesting that cytochrome bo3 might be the rate-limiting factor of the respiratory chain. The three transcriptome comparisons of G. oxydans M-NM-^TuppM-NM-^TcyoBACD vs. G.oxydans M-NM-^Tupp were repeated independently three times in biological replicates resulting in 3 hybridizations as termed by sample 1 to 3.

ORGANISM(S): Gluconobacter oxydans 621H

PROVIDER: E-GEOD-47782 | BioStudies |

REPOSITORIES: biostudies

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