[Carbon isotope fractionation by aerobic heterotrophic microorganisms]

The isotope effects of carbon were studied in auxotrophic mutants of the following aerobic microorganisms: Escherichia coli, Corynebacterium, Bacillus subtilis, Brevibacterium and Micrococcus glutamicus. Intramolecular isotope heterogeneity was found in position of the total carbon differed from that of the carbon of the carboxyl in the amino acid. In the lysine released by Corynebacterium grown on acetate, the carboxyl carbon is enriched with 13C by 8%o comparing with the total carbon of the amino acid; in the lysine liberated by Brevibacterium flavum, the carboxylic carbon is enriched with 13C by 3.5%o. These and other peculiarities of the intramolecular distribution of carbon isotopes in amino acids should be attributed to diverse pathways of their biosynthesis in different organisms.