Relation Between the Rate of Growth of a Mutant Strain of Escherichia coli and the Efficiency of Its Utilization of Arginine

Abstract

A mutant strain of Escherichia coli that requires the addition of arginine for growth was isolated in this laboratory by Roepke et. al. (1944) following serial transfer of the parent culture in a complete medium. This strain (1572-228)2 is unable to utilize citrulline or ornithine for growth even in the presence of limiting concentrations of arginine.3 During studies on the determination of arginine by the use of this mutant strain, we observed that the final turbidity reached by the organism with limiting concentrations of arginine was decreased by the addition of an arginine-free mixture of amino acids and growth factors or of a yeast extract preparation which had been freed of arginine by alkaline hydrolysis. This effect of supplements was similar to that noted in experiments with mutant 532-171, which requires the addition of methionine for growth (Lampen et al., 1947).This report deals with the conditions under which the decreased final turbidity is observed and the effect of this phenomenon on the assay of arginine in protein hydrolyzates. EXPERIMENTALThe basal medium (glucose, asparagine, and salts) and the general methods employed have been reported previously (Lampen et al., 1947). Arginine-low natural materials were prepared by alkaline hydrolysis. This treatment converts arginine to citrulline and ornithine (Fox, 1938). Ten-gram samples of Difco yeast extract or of Difco peptone were dissolved in 100 ml of 5 N NaOH and autoclaved at 15 pounds' pressure for 1 hour and for 3 hours. The hydrolyzates were neutralized with 10 N H2SO4 and diluted to 200 ml. Each ml was then equivalent to 50 mg of the original material. The yeast extract had contained 0.16 per cent arginine (by assay with the mutant strain) before hydrolysis and the peptone 3.9 per cent. After 1 hour of hydrolysis the yeast extract did not support growth of the mutant at concentrations to 50 mg per 10 ml (< 0.02 per cent arginine) whereas the peptone still contained 0.2 per cent arginine after 3 hours. A yeast extract sample hydrolyzed 1 hour was employed in the experiments described here.

Quantitative studies on mutants of Bacterium aerogenes requiring nicotinic acid and histidine

“…The medium contained casein hydrolysate, carbohydrate and mineral salts. The quantitative response ofa mutant of E8cherichia coli requiring arginine to the presence of arginine in simple medium and in the presence ofprotein hydrolysates has also recently been reported by Lampen & Jones (1947). As a preliminary study of the suitability of such mutants for use in microbiological assay the quantitative response of certain spontaneous and X-ray induced mutants of Bacterium aerogenes (Aerobacter aerogenes) to nicotinic acid and to histidine has been investigated.…”