Significance of hydrogen burst from growing cultures of Desulfovibrio vulgaris, Miyazaki, and the role of hydrogenase and cytochrome c3 in energy production system

Abstract

In an early stage of the growth of Desulfovibrio vulgaris, Miyazaki, a burst of H2 occurred, and lasted for a few hours. The H2S production which paralleled the cell proliferation was very low in the H2 burst period, and began to increase thereafter. Hydrogenase (hydrogen: ferricytochrome c3 oxidoreductase, EC1. 12.2.1), cytochrome c3 and desulfoviridin also increased after the H2 burst. These phenomena were common to all the cultural conditions tested, i.e., the cell growth is always preceded by the initial H2 burst. Hydrogenase of cells harvested in the H2 burst peroid was composed mainly of the high molecular weight species (mol. wt., 180,000), whereas that of the cells harvested later was composed of both the high molecular weight and the low molecular weight (mol. wt., 70,000) species. It was suggested that the former enzyme was acting as a catalyzer in the initial H2 burst to effect the substrate level phosphorylation during the breakdown of lactate to acetate and CO2, whereas the latter was induced by the H2 produced by the cells themselves to recycle H2 in order to supply electrons to the reducing system of sulfur oxy-acids coupled to electron transfer phosphorylation. The amount of cytochrome c3 in cells harvested from an iron-deficient medium was as high as that in cells harvested from an iron-rich medium, suggesting the significance of this electron carrier in the cellular metabolism.