Barile, Michael F. (Division of Biologics Standards, National Institutes of Health, Bethesda, Md.), Robert T. Schimke, and Donald B. Riggs . Presence of the arginine dihydrolase pathway in Mycoplasma . J. Bacteriol. 91 :189–192. 1966.—The presence of the arginine dihydrolase pathway was examined in 61 Mycoplasma strains representing at least 18 Mycoplasma species isolated from nine different sources: human, bovine, avian, murine, swine, goat, canine, sewage, and tissue cell culture origin. Some species were represented by only one or two strains. Different strains of the same species gave the same results. Ten species (56%) were positive. Many nonpathogenic Mycoplasma species ( M. hominis , type 1 and 2, M. fermentans, M. salivarium , and M. gallinarum ) were positive, whereas most pathogenic species ( M. pneumoniae, M. gallisepticum, M. neurolyticum , and M. hyorhinis ) were negative. The presence of arginine dihydrolase activity among Mycoplasma species may prove to be useful for purposes of identification and classification.

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B3ARILE, MICHAEL F. (National Institutes of Health, Bethesda, AMd.), WX ALTER F. iMALIZIA, AND DONALD B. RIGGS. Incidence and detection of pleuropneumonia-like organisms in cell cultures by fluorescent antibody and cultural procedures. J. Bacteriol. 84:130-136. 1962-A total of 102 tissue-cell cultures from 17 separate laboratories was examined for pleuropneumonia-like organisms (PPLO) by the fluorescent antibody and cultural procedures. PPLO were isolated from 48 of the 49 tissue-cell cultures found positive for PPLO by the fluorescent antibody l)rocedure, and results of the two procedures agreed in 101 of the 102 (99%) cases. PPLO were isolated from none of 10 primary-cell cultures prepared from six animal species and from 48 of 92 (52%) continuous-cell cultures prepared from eight animal species. Cells grown in media containing antibiotics were more frequently contaminated with PPLO (72%) than cells grown in antibiotic-free media (7 %). Cultures (91%) from tissue-cultureproducing laboratories and cultures (76%) used for propagation of microorganisms were contaminated with PPLO, although none used for tissueculture metabolic studies was contaminated. In addition, our findings support the view that PPLO contamination of cell cultures is probably owing to bacterial contaminants which revert to L forms in the presence of antibiotics. Continuous tissue-cell cultures are frequently contaminated with pleuropneunmonia-like organisms (PPLO) or L forms of bacteria or both