Hydrogenase activity and proton-motive force generation by Escherichia coli during glycerol fermentation

• Published in: Journal of bioenergetics and biomembranes 2013-06, Vol.45 (3), p.253-260
• Main Authors: Trchounian, Karen, Blbulyan, Syuzanna, Trchounian, Armen
• Format: Article
• Language: English
• Subjects: Animal Anatomy; Animal Biochemistry; Biochemistry; Bioenergetics; Bioorganic Chemistry; Carboxyl and Carbamoyl Transferases - genetics; Carboxyl and Carbamoyl Transferases - metabolism; Chemistry; Chemistry and Materials Science; Cryoprotective Agents - metabolism; Cryoprotective Agents - pharmacology; E coli; Enzymes; Escherichia coli; Escherichia coli - enzymology; Escherichia coli - genetics; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Fermentation; Glucose - genetics; Glucose - metabolism; Glycerol - metabolism; Glycerol - pharmacology; Histology; Hydrogen-Ion Concentration; Hydrogenase - genetics; Hydrogenase - metabolism; Membranes; Morphology; Mutation; Organic Chemistry; Proton-Motive Force - drug effects; Proton-Motive Force - physiology; Proton-Translocating ATPases - genetics; Proton-Translocating ATPases - metabolism
• ISSN: 0145-479X; 1573-6881
• DOI: 10.1007/s10863-012-9498-0

Proton motive force (Δp) generation by Escherichia coli wild type cells during glycerol fermentation was first studied. Its two components, electrical—the membrane potential (∆φ) and chemical—the pH transmembrane gradient (ΔpH), were established and the effects of external pH (pH ex ) were determined. Intracellular pH was 7.0 and 6.0 and lower than pH ex at pH 7.5 and 6.5, respectively; and it was higher than pH ex at pH 5.5. At high pH ex , the increase of ∆φ (−130 mV) was only partially compensated by a reversed ΔpH, resulting in a low Δp. At low pH ex ∆φ and consequently Δp were decreased. The generation of Δp during glycerol fermentation was compared with glucose fermentation, and the difference in Δp might be due to distinguished mechanisms for H + transport through the membrane, especially to hydrogenase (Hyd) enzymes besides the F 0 F 1 -ATPase. H + efflux was determined to depend on pH ex ; overall and N,N’ -dicyclohexylcarbodiimide (DCCD)-inhibitory H + efflux was maximal at pH 6.5. Moreover, ΔpH was changed at pH 6.5 and Δp was different at pH 6.5 and 5.5 with the hypF mutant lacking all Hyd enzymes. DCCD-inhibited ATPase activity of membrane vesicles was maximal at pH 7.5 and decreased with the hypF mutant. Thus, Δp generation by E. coli during glycerol fermentation is different than that during glucose fermentation. Δp is dependent on pH ex , and a role of Hyd enzymes in its generation is suggested.