Methylammonium as a substrate for autotrophic growth by wild type Thiobacillus versutus, and mutant strains with lesions in chemolithotrophic metabolism.

Methylammonium consumption and ribulose 1-5-bisphosphate carboxylase (RuBisCO) activity were monitored in cultures of wild type Thiobacillus versutus and mutants deficient in autotrophic metabolism grown under various growth conditions. Only mutants 22, 72, 73 (deficient in ability to oxidize thiosulphate) could grow and develop RuBisCO activity on methylammonium, and assimilate 14CO2 generated as a result of methylammonium metabolism. Mutants 40 and 76, deficient in autotrophic CO2 fixation, showed no 14C methylammonium assimilation and did not oxidize it as a sole substrate within normal incubation periods. Relations of substrate metabolism and RuBisCO regulation in cultures grown on mixtures of thiosulphate or sucrose and methylammonium are described. Further genetic analysis of mutants with defects in autotrophic metabolism may allow localisation of genes responsible for the metabolic effects described.