THE DEVELOPMENT OF PROTEUS CULTURES IN THE PRESENCE OF PENICILLIN

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Abstract
Tiny pleuropneumonia-like colonies that were previously descr. in Proteus were grown with the help of penicillin to larger size and could be maintained indefinitely in subculture. The appropriate composition of the medium is of great importance for the growth of these colonies. Multiplication of most freshly isolated Proteus strains is inhibited in the usual bacillary forms by the addition of 10-50 U./ml. penicillin. However on soft horse-serum agar plates in the course of a few days colonies develop in media containing up to 10,000 U./ml. They grow in 2 distinct types. One type remains small on the original plate (0.05-0.2 mm.) and grows easily in transplants whether or not penicillin is present. If penicillin is absent, the usual bacillary form of Proteus reappears after a variable time up to several weeks. The colonies of the 2d type are larger (1 to 3mm.). Transferred to penicillin-free media, they reproduce the usual bacillary forms within a few hrs. On media containing penicillin, they produce an abundant growth of the small colonies with an occasional large colony. Carboxymethoxylamine had an effect similar to that of penicillin and induced growth of L colonies. The effect was quantitatively much less than that of penicillin.