THE RELATIONSHIP OF A TYPE OF MYCOPLASMA ISOLATED FROM TISSUE CULTURES TO A NEW HUMAN ORAL MYCOPLASMA

Presence of the arginine dihydrolase pathway in Mycoplasma

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.

Osmolar concentration and fixation of mycoplasmas

Broth cultures of Acholeplasma laidlawii were fixed with various concentrations of cacodylate-buffered glutaraldehyde. The shape and ultrastructure of the organisms varied with the osmolar concentration of the fixative. When the fixation mixture was hypertonic to the culture medium, ultrathin sections suggested that the cells had shrunk. Phosphate buffer, sodium chloride, or sucrose at comparable osmolaities had the same effect as sodium cacodylate. Glutaraldehyde itself also contributed to the osmotic effects of the fixation mixture but to a lesser extent than salts or sucrose, to which the cell membrane is impermeable. The osmolar concentration of the fixation mixture seemed of greater importance than pH in determining morphology. The mycoplasma was still susceptible to damage by high concentrations of cacodylate after fixation with 2.5% glutaraldehyde. The best procedure was to fix and wash the organism under conditions isotonic with the growth medium. These conditions were also satisfactory for a filamentous mycoplasma, Mycoplasma orale.

New assay procedure for separation of mycoplasmas from virus pools and tissue culture systems

Presence of mycoplasma organisms in tissue culture systems and virus pools was detected by titration of the contaminated material on agarose-suspended BHK21/13S cells. The use of this method permitted isolation of mycoplasmas which could not be detected by standard assay methods. Mycoplasma colonies at concentrations ranging from 10(4) to 10(6) colony-forming units/ml in agarose-BHK21/13S media could be distinguished from virus plaques, and the two populations of microorganisms could be easily disassociated either by electron microscopy or by biological methods. All isolated mycoplasmas were identified in growth inhibition tests as belonging to the GDL group. The growth inhibition test on agarose-BHK21/13S cell suspension plates could also be applied directly to those strains which could not be isolated by standard assay procedures.