Ability to demonstrate clearly the sequence of events during division by observing live cells might hasten the settlement of the controversy over the mechanism of bacterial nuclear division. Phase contrast microscopy of living bacteria

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Park, Calif.). Metabolism of animal cells infected with mycoplasma. J. Bacteriol. 82:288-297. 1961.-The effect of pleuropneumonia-like organisms (PPLO) upon the metabolism of tissue cultures was tested by comparing the assimilation and accumulation of the amino acids in the medium during growth and maintenance of monolayers of mouse fibroblasts (L strain) and human bone marrow cells (Mox). This preliminary study indicates that PPLO do alter the amino acid metabolism of animal cells. The observed changes in metabolic patterns shown by the infected fibroblast cultures did not mirror the metabolic patterns of the PPLO in the medium alone. Different strains of animal cells showed different responses to one PPLO strain, and different strains of PPLO caused different responses in one strain of animal cells. The PPLO did not grow in the tissue culture medium (no. 199 plus 2% horse serum and 20 to 40 units of penicillin/ml) nor in spent culture fluids and rapidly died off at 37 C but survived for months at 4 C. The altered metabolism of the infected tissue cultures appeared to reflect a true host-parasite interaction.