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 (). Wild-type cells, grown aerobically in the presence of heme, generated a even in the presence of the F1-Fo ATPase inhibitor N,N'-dicyclohexylcarbodiimide, while a cytochrome bd-negative mutant strain (CydA) did not. We also observed high oxygen consumption rates by membrane vesicles prepared from heme-grown cells, compared to CydA 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.
- electrochemical proton gradient
- complete genome sequence
- cytochrome bd
- acid bacteria
- respiration metabolism
- environmental heme
Brooijmans, R. J. W., Poolman, B., Schuurman-Wolters, G. K., de Vos, W. M., & Hugenholtz, J. (2007). Generation of a membrane potential by Lactococcus lactis through aerobic electron transport. Journal of Bacteriology, 189(14), 5203-5209. https://doi.org/10.1128/JB.00361-07