Isolation, antifungal activity and characterization of soil actinomycetes

Actinomycetes were isolated from eight samples of two different habitats, i.e., garden soil and cultivated field soil. Isolation of actinomycetes was carried out on soil extract agar medium using serial dilution method and forty seven isolates were obtained. All these actinomycetes were then assessed for their antifungal activity against two fungal pathogens i.e., Candida albicans and Aspergillus niger by cross streak method. Eleven actinomycetes were found to inhibit A. niger. Out of 11 actinomycetes, only 6 showed antifungal activity against both test organisms. On the basis of screening, one potential actinomycete GS 22 was selected for further studies. The antibitiotic was extracted with methanol from cellular extract of actinomycete GS 22. The extract of GS 22 culture filtrate produced a clear zone of 27 mm against C. albicans by agar well diffusion method. Actinomycete strain GS 22 was further characterized on the basis of morphological, biochemical and physiological characteristics and identified using probabilistic identification of bacteria (PIBWin) software as Streptomyces phaeochromogenes.