Utilization of amino acids as a source of nitrogen by Hydrogenomonas eutropha.

Relatively little has been published on the capacity of Hydrogenomonas to utilize amino acids under conditions supporting either autotrophic or heterotrophic growth. DeCicco and Umbreit (4) found that wild-type H. facilis utilizes either phenylalanine or tyrosine for growth with glucose as the main carbon and energy source. Atkinson (2) noted that H. facilis growing autotrophically in the presence of L-glutamate as the sole source of nitrogen uses 02 at a rate equal to that with NH4Cl. Mutant strains of H. eutropha, recently isolated by DeCicco and Stukus (3), require histidine, tryptophan, methionine, cysteine, or phenylalanine plus tryptophan for growth. This paper describes an experimental study of the ability of wild-type H. eutropha to utilize a variety of amino acids as a sole nitrogen source under autotrophic growth conditions. The L isomers of the amino acids were employed in these experiments and were obtained from Nutritional Biochemical Corp., Cleveland, Ohio. H. eutropha was obtained from the culture collection of D. Davis, Department of Bacteriology, University of California, Berkeley. The basal culture medium (1) was modified to contain 0.1 M phosphate buffer (pH 6.8). The amino acids were individually added in the amount of 0.1 g of N/liter, except for cystine (0.025 g of N/liter) and tyrosine (0.05 g of N/liter). Controls included: (i) a mixture of NH4C1 (0.05 g of N/liter) and NH40H (0.05 g of N/liter) and (ii) basal medium to which no nitrogen source was added. The NH40H counteracted a decrease in pH which occurred during ammonia utilization when only NH4Cl was present in the buffered medium. The pH did not change with the addition and utilization of the amino acids. All media were sterilized by filtration through Pyrex ultrafine sintered glass. The solution of FeCl3.6H20 was filtered separately and was added after the rest of the components had been sterilized. All experiments were made in a series of eight