Defined medium for Aquaspirillum serpens VHL effective in batch and continuous culture

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Abstract
A defined medium for A. serpens VHL allows the replacement of the complex media now in use. It was developed by batch culture methods but supports growth in continuous culture. A basal salts medium supplemented with L-aspartic acid, L-alanine and L-glutamic acid provided the best growth (turbidity), as long as ammonium chloride was omitted. Ammonium chloride caused a lag or a reduction or a complete inhibition of the growth of A. serpens VHL on the above amino acids and other organic supplements depending on the combination used. Ammonium sulfate and ammonium hydroxide with L-glutamic acid allowed growth, but the lag period was increased in shake flask cultures. Vitamins, cysteine hydrochloride and CO2 had no effect on the growth rate. Viability (less than 50%) was inadequate to maintain continuous culture with L-glutamic acid as the sole source of C and N. Combinations of amino and carboxylic acids were then tested and, of these, L-glutamic acid (1 g/l) and L-histidine (75 mg/l) without ammonium chloride in the basal salts medium supported growth in batch and continuous culture. L-Glutamic acid was the limiting substrate for growth.