A Consolidated Method for Selective Isolation of Actinomycetes Based on Choice of Substrate

Actinomycetes are known as filamentous, Gram positive bacteria. They form the majority of the microbial load in various niches; soils, composts, etc. The study aimed to evaluate the method of isolating slow growing actinomycetes from four different sources: garden soil, cow dung manure compost, floral waste compost, and floral waste vermicompost. In this study, an integrated method consisting of physical and chemical pretreatment of the sample and the use of selective media was used to isolate actinomycetes. Physical treatment includes air drying, sun drying, dry heating in an oven, and moist heat treatment, whereas chemical treatment includes enrichment of the sample with CaCO3 followed by plating on actinomycetes-specific media with the incorporation of antibacterial and antifungal antibiotics. The actinomycetes count on the plate was reported in CFU/gm of dry wt. Morphological and microscopic characteristics of purified isolates were noted. The results were compared, and it was found that the pretreatment method of a particular sample depends on the choice of substrate. Overall, physical treatment followed by chemical enrichment showed relatively higher counts on the plate and better results. Here we also found the dominance of fluorescent Pseudomonas sp. in case samples from vermicompost. The study can be of great importance in isolating novel and rare genera of actinomycetes. These methods can help speed up the isolation and screening of novel actinomycetes which will ultimately be important for the discovery of antibiotics and other industrially vital bioactive compounds.