MINIMAL MEDIA FOR QUANTITATIVE STUDIES WITH BACILLUS SUBTILIS

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Abstract
The need for a suitable minimal medium for colony formation by B. subtilis (Warburg strain), especially for genetic studies, was demonstrated. Washed spore suspensions required L-alanine, L-asparagine, and L-glutamic acid. The main role of alanine and asparagine was that of stimulating germination while glutamic acid was needed for outgrowth and vegetative growth. The newly devised spore minimal medium gave complete colony formation with B. subtilis and also supported colonial growth of B. brevis, B. macerans, and B. natto but it was deficient for B. cereus. For colony formation by washed vegetative cells, glutamic acid and either ethylenediaminetetraacetate or cysteine were required. A new vegetative minimal medium, containing such a supplement, gave maximal plate counts of B. subtilis. The medium was slightly less effective for B. brevis, B. macerans, and B. natto, B. cereus developed poorly on it. These studies also emphasized the need for mineral salts during washing and diluting vegetative cells. Tap water, distilled water, and physiological saline killed the vegetative cells at an extremely rapid rate.