Abstract
MANY soil actinomycetes of the genus Streptomyces inhibit the growth of fungi on solid agar media, the inhibitory power exerted by a colony of such an actinomycete on a neighbouring fungal colony being indicated by the width of the inhibition zone which forms between them. Since the width of this zone is affected by the size and relative positions of the two colonies, it is essential to standardize these conditions in order to compare the anti-fungal activity of an actinomycete on different media. Actinomycetes grow slowly by comparison with most fungi; hence, when making an antagonism test of this type, it is convenient to inoculate the actinomycete over an area of the agar surface upon which will arise a colony large enough to give an easily measurable inhibition zone in a short time. Colonies 5–10 mm. in diameter when three to five days old have been found to be quite suitable. The technique of placing aliquot drops of liquid inoculum directly on an agar surface is sometimes not satisfactory, because the drops may spread, particularly when the plate is moved, thereby giving rise to irregular colonies. Moreover, the amount of spreading is affected by the composition of the medium. Again, it is sometimes necessary to inoculate with the actinomycete after the fungus has grown for some time on the plate. In such cases it is difficult to place the drops at a predetermined distance from the fungal growth.
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References
Heatley, N. G., Biochem J., 38, (1), 61 (1944).
Jackson, W. Foster, and Woodruff, H. B., J. Bact., 47, (1), 43 (1944).
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SKINNER, F. Preparation of Standardized Actinomycete Colonies. Nature 166, 314 (1950). https://doi.org/10.1038/166314a0
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DOI: https://doi.org/10.1038/166314a0
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