Use of carboxylic acids by Thiobacillus A2

Thiobacillus A2 can grow on acetate, glycollate, succinate and citrate as sole carbon and energy sources. Results of growth and transport experiments indicated that separate transport systems existed for the four acids although acetate uptake by bacteria grown on glycollate was very rapid. Citrate was a potentially toxic substrate in that low concentrations had to be supplied to adapt organisms to growth on citrate following autotrophic culture on thiosulphate. Apparent Ks values for transport by whole organisms were around 10(-4) M. The effects of uncoupling agents, phosphate and arsenate, on acid uptake did not allow identification of the mechanisms of transport, but indicated energy-requiring processes possibly involving anion participation. The ratio of carbon assimilated from the -CH2- and the -COOH carbons of succinate was about 5:1, reflecting very rapid decarboxylation of succinate following uptake into the cell.