Metabolism of animal cells infected with mycoplasma

ARGININE METABOLISM IN PLEUROPNEUMONIA-LIKE ORGANISMS ISOLATED FROM MAMMALIAN CELL CULTURE

Schimke, Robert T. (National Institutes of Health, Bethesda, Md.) and Michael F. Barile. Arginine metabolism in pleuropneumonia-like organisms isolated from mammalian cell culture. J. Bacteriol. 86:195-206. 1963.-Arginine degradation is a significant metabolic process for pleuropneumonia-like organisms (PPLO; Mycoplasma) isolated from cell culture. The conversion of arginine to ornithine in PPLO-contaminated cell culture was rapid, and occurred by the arginine dihydrolase pathway involving arginine deiminase, ornithine transcarbamylase, and carbamyl phosphokinase. In the absence of PPLO contamination, arginine conversion to ornithine was minimal and took place by an arginase activity present in the cell culture, but not in the PPLO. All five PPLO strains isolated from cell culture accomplished the conversion of arginine to ornithine, and contained the requisite enzyme of the arginine dihydrolase system, whereas PPLO-free cell cultures did not. Supplementation of PPLO culture broth with arginine increased the extent of PPLO growth. When the arginine content of the culture limited growth, arginine was completely converted to ornithine. When growth was limited in the presence of excess arginine, citrulline was the major breakdown product. It is suggested that the conversion of arginine to ornithing constitutes a significant, and possibly major, source of adenosine triphosphate for this class of organisms.

AEROSOLS AS A SOURCE OF WIDESPREAD MYCOPLASMA CONTAMINATION OF TISSUE CULTURES

Mycoplasma isolates were cultured from 15 antibiotic-free cell cultures obtained from a single laboratory. Complement-fixation tests showed that these isolates were antigenically related to each other but were unrelated to M. hominis type 1, M. hominis type 2, M. arthritidis, M. laidlawii type B, Mycoplasma sp. H.Ep. #2 (Barile), or M. salivarium. Examination of serum used to feed the infected cell lines revealed no Mycoplasma. Infection resulting from cross-contamination by a single Mycoplasma strain from one cell culture to another was investigated. Although the organisms were not found in the air over the work area, aerosols containing these contaminants were produced in tissue culture bottles during the trypsinization of cell monolayers. The minimal infectious dose of Mycoplasma for tissue cultures was measured, and it was determined that one organism was capable of initiating an infection in a tissue culture. The pattern of contamination and the small dose required for infection indicated that Mycoplasma contamination was spread from one tissue culture to another via aerosols. It was demonstrated that Mycoplasma can be transferred from one cell culture to another through the use of a common burette for dispensing medium.

TEM and SEM findings in cat fibroblasts cultivated in vitro with and without Mycoplasma

Mycoplasma contamination of cultured cells may cause considerable interference with their behaviour and metabolism. Whether or not mycoplasma are actually taken up by cells in vitro has long been a matter of dispute. In the present study mycoplasma were shown to phagocytosed by feline lung fibroblasts and to end up in the lysosomal vacuome of the cells, where the organisms were only partially degraded by the hydrolytic enzymes leading to a rapid (within a few days) accumulation of secondary lysosomes of the residual body variety. It is thus obvious that studies on the structure and function of the lysosomal vacuome in cultured cells are possible only if precautions are taken to avoid that the cultures become contaminated by mycoplasma.

Mycoplasmas and cell cultures

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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.