Summary: The particulate NADH oxidase activity of is inhibited by tyro-cidine and the kinetics of inhibition indicate that the NADH dehydrogenase region is the primary site of action. A decrease in NADH oxidase activity of electron transport particles and of NADH oxidase activity of whole organisms occurs in batch culture in the later stages of growth when production of tyrothricin increases. That respiration exhibited by growing cells takes place via the respiratory electron-transport system is indicated by the similarities in levels of activity and cyanide sensitivity of endogenous and NADH oxidation of growing cells. Exponential growth on glycerol asparagine media is diphasic, a slower growth rate commencing as the O tension of the culture approaches zero and tyrothricin production increases. Molar growth yield data based on overall measurements of growth related to O uptake in batch culture lead to low ATP/O ratios. In an attempt to determine and ATP/O ratios under optimum conditions of growth a method is described which was based entirely on the growth and respiratory activity of exponentially growing cells. Such measurements led to higher values for and to ATP/O ratios approaching 3, indicating the participation of three sites of phosphorylation during exponential growth. Tyrocidine and DNP inhibited growth, the tyrocidine at concentrations similar to those produced at the end of the exponential growth phase. / ratios (ATP/O ratios) on glycerol asparagine media were lower than on peptone yeast extract medium which yielded no tyrothricin, a possible indication that some form of uncoupling occurs in organisms grown on glycerol asparagine medium which does not yield tyrothricin.


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