Chloromycetin and Growth of Certain Protozoa

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Abstract
Good cultures of Euglena gracilis (colorless) developed in all concns. of chlormycetin and including 3.32 mg. per ml. when the basic medium consisted of casitone and yeast extract. Growth was inhibited only slightly by concns. of 30 to 1500 [mu]g. per ml. Amounts of 2000 [mu]g. per ml. and higher depressed growth moderately. There appeared to be little difference when the green strain was used. In a medium without yeast extract, the green strain seemed to be less tolerant to the antibiotic. Amounts of 1000 ug. per ml. and higher markedly depressed the growth of E. viridis, although only slight inhibition was evident in the range from 30 to 600 [mu]g. per ml. Tetrahymena geleii strains H, L-1, and L-2 were sharply inhibited by 1000 [mu]g, and strain H by as little as 30 [mu]g. per ml. of chloromycetin. The highest concn. in which living ciliates were seen after 40 hours was 1750 [mu]g. per ml. Strain L-2. in a slightly different medium, did not tolerate as much and at 96 hours did not survive in 500 [mu]g. per ml., although it was viable in the 100 [mu]g. cultures. After 7 days, the H strain was motile in 30, but not viable in 60 [mu]g. per ml. In general, there appears to be little difference in chloromycetin tolerance of the 3 strains. Max. growth of T. geleii is attained in a medium containing 100 [mu]g. per ml. of chloromycetin at about 70 hours. The results suggest that the protozoa may be suitable for investigations on the biochemistry of chloromycetin.