A defined medium has been developed for that gives growth characteristics (growth rate, maximum cell number and maximum colony-forming-unit count) comparable to those in a complex medium (Isosensitest broth+5%, v/v, foetal bovine serum). Differences found in the death rate reflected a partial (50%) conversion to a coccoid cell form of the organism in the stationary and death phase in the defined medium, versus the almost complete (> 99%) conversion seen in the complex medium. The medium was used to study the amino acids required for growth by 10 strains of All strains required arginine, histidine, isoleucine, leucine, methionine, phenylalanine and valine, and eight of the strains also required alanine; five of the strains required serine. In the absence of glucose none of the 20 amino acids tested elicited growth when added at high concentration. However, in the presence of glucose, alanine induced considerably enhanced growth over that seen in the control, consistent with its use either as a nitrogen source or possibly an additional carbon source. The medium described will facilitate investigations into the metabolism and physiology of , previously only possible with sophisticated approaches such as nuclear magnetic resonance spectroscopy.


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