Search for antagonistic Actinomycetae in Libyan soils

Abstract

The place of 135 streptomyces isolates from 39 soil specimens collected in different geographical regions of Libya has been determined in the scheme recommended by Pridham, Hesseltine, and Benedict. The streptomyces isolates fall into four groups of the system. The members of the grey series predominate, followed in order of frequency by the brown ones. The other series occur in negligible numbers. Section IV and VII were totally absent.Sixty-five percent of the isolates proved to be antagonists, including 50% active exclusively against Gram-positive, 3% active exclusively against Gram-negative, and 12% active equally against Gram-positive and Gram-negative microorganisms.A correlation between the organic content of the soil samples and the number of streptomyces was quite obvious. Soil richer in organic materials seem to contain fewer streptomyces strains than the poorer ones. The soils left untouched for long periods of time without cultivation may supply both numerically and qualitatively most of the antagonists.A rather interesting point is that in Libyan soils the incidence of antagonism to Gram-positive microorganisms is particularly high when compared with that in the other areas of the world.