Studies on relationships between flagellar motility and oxidative fermentation by acetic acid bacteria

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Oxidative fermentation by acetic acid bacteria, where substrates are oxidized by the respiratory chain-linked dehydrogenases, accumulates oxidation products to the culture medium, such as acetic acid from ethanol. Such incomplete oxidation produces proton motive force across the membrane for energy to drive ATP synthesis and others. Flagella are locomotive organelles of bacteria, which require proton motive force at work. This study hypothesizes that energy metabolism is crucial in the oxidative fermentation. Thus, the flagellar motility of acetic acid bacteria was modulated to see effects on the oxidative fermentation. This study found that (i) the motB1 gene is involved in the flagellar motility through reverse genetic approach. (ii) The flagellar motility of acetic acid bacteria is induced by acetic acid as well as under nutrient rich conditions in the late growth phase. (iii) Acetic acid fermentation study using immotile mutant and over producing mutant strains revealed that the immotile mutant grew better than wild type but produced acid at almost same levels of wild type. The data suggest that acid productivity per cell of the immotile mutant is worse than that of wild type, and thus positive correlation between motility and oxidative fermentation.