Growth Phases of Mycoplasma in Liquid Media Observed with Phase-Contrast Microscope

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Abstract
Growth of 11 Mycoplasma strains in liquid media was followed by phase-contrast microscopy. A similar pattern of development was common to all strains. Branching filaments, 0.3 to 0.4 [mu] thick, characterized the early logarithmic phase of growth. The length of the filaments varied according to the strain tested and the growth medium. Addition of oleic acid to the medium induced the formation of very long filaments by M. laidlawii strain-B. Upon aging, the filaments were found to break up into chains of coccoid elements. These chains further fragmented to yield shorter chains and single coccoid elements, which characterized the stationary and decline phases of growth. The size of the coccoid elements increased from 0.3 to 0.4 [mu], when formed in the filaments, to 0.6 to 0.8 [mu]. after being released from the chains. Further increase in the size of the cells took place at the decline phase of growth, leading to the formation of very large cells reaching a diameter of 10 to 20 [mu]. However, these large cells had the appearance of empty vesicles and were apparently nonviable as indicated by viable-count experiments.

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