Utilization of l-alanine as carbon and nitrogen source by Deusulfovibrio HL21.

Desulfovibrio HL21 is unable to grow with amino acids as energy substrates. Alanine, serine, aspartate and to some extent glutamate were used as carbon and nitrogen sources in the presence of hydrogen as the energy substrate. Dense cell suspensions converted alanine stoichiometrically to acetate, NHand presumably HCO, but at a very low rate. Desulfovibrio HL21 cells grown with alanine as carbon and nitrogen source contained increased levels of NAD(P)-dependent l-alanine dehydrogenase as compared to cells grown with NHCl as nitrogen source. Unfavourable kinetic properties of this alanine dehydrogenase, repression of the synthesis of the enzyme by NHand a low rate of NADH oxidation all have a negative effect on the rate of degradation of alanine and may partly explain the inability of the strain to grow with alanine as an energy substrate. [ABSTRACT FROM AUTHOR]