title: Generation of a membrane potential by Lactococcus lactis through aerobic electron transport.
abstract: Lactococcus lactis, a facultative anaerobic lactic acid bacterium, is known to have an increased growth yield when grown aerobically in the presence of heme. We have now established the presence of a functional, proton motive force-generating electron transfer chain (ETC) in L. lactis under these conditions. Proton motive force generation in whole cells was measured using a fluorescent probe (3',3'-dipropylthiadicarbocyanine), which is sensitive to changes in membrane potential (Delta psi). Wild-type cells, grown aerobically in the presence of heme, generated a Delta psi even in the presence of the F(1)-F(o) ATPase inhibitor N,N'-dicyclohexylcarbodiimide, while a cytochrome bd-negative mutant strain (CydA Delta) did not. We also observed high oxygen consumption rates by membrane vesicles prepared from heme-grown cells, compared to CydA Delta cells, upon the addition of NADH. This demonstrates that NADH is an electron donor for the L. lactis ETC and demonstrates the presence of a membrane-bound NADH-dehydrogenase. Furthermore, we show that the functional respiratory chain is present throughout the exponential and late phases of growth.
authors.affiliation: Kluyver Centre for Genomics of Industrial Fermentation, Wageningen Centre for Food Sciences, Wageningen, The Netherland.
authors.forename: R J W
authors.initials: RJ
authors.lastname: Brooijmans
authors.forename: B
authors.initials: B
authors.lastname: Poolman
authors.forename: G K
authors.initials: GK
authors.lastname: Schuurman-Wolters
authors.forename: W M
authors.initials: WM
authors.lastname: de Vos
authors.forename: J
authors.initials: J
authors.lastname: Hugenholtz
mesh_terms: D000332:Aerobiosis; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004579:Electron Transport / Q000235:genetics / Q000502:physiology; D005453:Fluorescence; D006418:Heme / Q000378:metabolism / Q000494:pharmacology; D013294:Lactococcus lactis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008954:Models, Biological; D009154:Mutation; D009243:NAD / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D013696:Temperature
chemical_list: D009243:NAD; D006418:Heme; D009245:NADH Dehydrogenase; D010100:Oxygen