title: Mechanism of increased respiration in an H+-ATPase-defective mutant of Corynebacterium glutamicum.
abstract: We previously reported that a spontaneous H(+)-ATPase-defective mutant of Corynebacterium glutamicum, F172-8, derived from C. glutamicum ATCC 14067, showed enhanced glucose consumption and respiration rates. To investigate the genome-based mechanism of enhanced respiration rate in such C. glutamicum mutants, A-1, an H(+)-ATPase-defective mutant derived from C. glutamicum ATCC 13032, which harbors the same point mutation as F172-8, was used in this study. A-1 showed similar fermentation profiles to F172-8 when cultured in a jar fermentor. Enzyme activity measurements, quantitative real-time PCR, and DNA microarray analysis suggested that A-1 enhanced malate:quinone oxidoreductase/malate dehydrogenase and l-lactate dehydrogenase/NAD(+)-dependent-lactate dehydrogenase coupling reactions, but not NADH dehydrogenase-II, for reoxidation of the excess NADH arising from enhanced glucose consumption. A-1 also up-regulated succinate dehydrogenase, which may result in the relief of excess proton-motive force (pmf) in the H(+)-ATPase mutant. In addition, the transcriptional level of cytochrome bd oxidase, but not cytochrome bc(1)-aa(3), also increased, which may help prevent the excess pmf generation caused by enhanced respiration. These results indicate that C. glutamicum possesses intriguing strategies for coping with NADH over-accumulation. Furthermore, these mechanisms are different from those in Escherichia coli, even though the two species use similar strategies to prevent excess pmf generation.
authors.affiliation: Laboratory of Microbial Physiology, Research Faculty of Agriculture, Hokkaido University, Kita-9 Nishi-9, Kita-ku, Sapporo, Hokkaido 060-8589, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Sawada
authors.forename: Yui
authors.initials: Y
authors.lastname: Kato
authors.forename: Keita
authors.initials: K
authors.lastname: Imai
authors.forename: Liyuan
authors.initials: L
authors.lastname: Li
authors.forename: Masaru
authors.initials: M
authors.lastname: Wada
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Matsushita
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yokota
mesh_terms: D048230:Corynebacterium glutamicum / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D004579:Electron Transport / Q000235:genetics; D005285:Fermentation; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D009243:NAD / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000235:genetics*
chemical_list: D009243:NAD; D010088:Oxidoreductases; D006180:Proton-Translocating ATPases