Effect of p H on Human Mycoplasma Strains

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Abstract
Shepard, Maurice C. (U.S. Naval Medical Field Research Laboratory, Camp Lejeune, N.C.), and Carl D. Lunceford . Effect of p H on human Mycoplasma strains. J. Bacteriol. 89: 265–270. 1965.—The optimal reaction of culture media for the cultivation of T-strain Mycoplasma of human origin was investigated. By use of a recently modified tryptic digest medium, the optimal reaction in either agar or fluid medium was found to be p H 6.0. In contrast, human classic (large-colony) Mycoplasma could be cultivated in agar or fluid medium over a rather broad p H range, and the influence of the reaction of the medium appeared to be primarily species-dependent. M. salivarium , for example, grew best in agar from p H 5.5 through 6.5. M. pneumoniae (Easton's agent) yielded largest colony numbers in agar and highest titers in broth at p H 8.0. In the case of T-strain Mycoplasma , both maximal colony numbers in agar and highest titers in fluid media were achieved at a reaction of p H 6.0. In addition, largest colony size of T-strain Mycoplasma was also achieved in agar at p H 6.0, and averaged 50 to 100% larger than that obtained by cultivation at p H 8.0 with the same medium. Although T-strains will develop in agar media over a p H range of from 5.0 through 10.0, the extremely small colony size and poor staining properties resulting from growth in an alkaline medium make their recognition in agar cultures difficult. Aerobic cultivation of T-strains was first achieved in agar adjusted to p H 5.5 to 6.0. In fluid medium, multiplication of T-strains occurred only within the limits of p H 5.0 through 8.0, with highest titers being reached at p H 6.0. Greater attention to the reaction of complete Mycoplasma media is stressed.