A study of the antibiotic activity of actinomycetes from soils of northern Canada.

Of 660 cultures of actinomycetes isolated on a nonselective basis from soils from five locations in Northern Canada, 404 strains, or 61.2%, showed antagonism against at least one of eight test organisms consisting of five bacteria and three plant pathogenic fungi. The degree of activity ranged from slight to strong, with the number of test organisms inhibited by any single culture varying from one to six. In all, 49 different antibiotic spectra were observed. Activity against one or more of the pathogenic fungi was shown by 138 cultures, 20.9% of the isolates. The percentage of active cultures was greater, and the degree of inhibition much more marked, against Helminthosporium sativum than against Fusarium culmorum or Fusarium lini. The percentage of active isolates varied with the location and with the depth of the soil. It is suggested that the high proportion of actinomycetes with antagonistic properties occurring in northern soils may be related to the lower degree of plant development in such regions.