Differential levels of ferredoxin and rubredoxin in Clostridium acetobutylicum

Ferredoxin and rubredoxin levels have been determined in DEAE-cellulose treated extracts of Clostridium acetobutylicum using specific enzymatic assays. In contrast to ferredoxin, the content of rubredoxin is affected by various culture conditions; it fluctuates in the proportions of 1 to 3 according to the growth phase, 1 to 8 according to the medium composition, and 1 to 40 according to the pH. Highest rubredoxin level is obtained at the end of the acid phase when the cells grow in chemically defined medium, the pH of which is not controlled. Such variations suggest that rubredoxin as well as rubredoxin-reductase take part in an electron transport chain system inducible by the culture conditions.