Lithotrophy to Organotrophy Conversion in Thiobacillus A2

SUMMARY: Thiobacillus A2 grown on thiosulphate lacks the capacity to transport succinate into the cells but is otherwise fully capable of oxidatively metabolizing succinate at a rapid rate. On the other hand, succinate-grown cells lack elements of the thiosulphate oxidation system; specifically, a special c-type cytochrome. Adaptation of thiosulphate-grown cells to succinate is characterized by a 30–40 min pause in growth during which time an efficient succinate transport system is produced and net cytochrome synthesis ceases. Resumed synthesis of cytochromes a and b parallels resumption of growth in cells newly adapted to succinate. By contrast, net synthesis of the characteristic c-type cytochrome of lithotrophic cells does not resume and the overall capacity to respire thiosulphate declines.