THE RESPIRATORY-CHAIN OF HELICOBACTER-PYLORI - IDENTIFICATION OF CYTOCHROMES AND THE EFFECTS OF OXYGEN ON CYTOCHROME AND MENAQUINONE LEVELS

The quinone and cytochrome components of the respiratory chain of the microaerophilic bacterium Helicobacter pylori have been investigated. The major isoprenoid quinone was menaquinone-6, with traces of menaqui none-l; no methyl-substituted or unusual menaquinone species were foun d. Cell yield was highest after growth at 10% (v/v) oxygen and menaqui none levels (per dry cell mass) were maximal at 5-10% (v/v) oxygen. He licobacter pylori cells and membranes contained b- and c-type cytochro mes, but not terminal oxidases of the a- or d-types, as judged by redu ced minus oxidised difference spectra. Spectra consistent with the pre sence of a GO-binding terminal oxidase of the cytochrome b- or o-type were obtained. The soluble fraction from disrupted cells also containe d cytochrome c. There were no significant qualitative differences in t he cytochrome complements of cells grown at oxygen concentrations in t he range 2-15% (v/v) but putative oxidases were highest in cells grown at 5-10% (v/v) oxygen.