ANTAGONISTIC ACTIVITY OF ACTINOMYCETES ISOLATED FROM KUALA

Abstract

Background: The screening for novel antimicrobial agents continues in a rather overlooked hunting ground for many researchers. Streptomyces is the best-recognized genus of actinomycetes used in the screening approach for novel antibiotic-producing microorganisms. The work is aimed to isolate bioactive actinomycete strains and identify the most potent isolates. Methods: forty-one actinomycete strains were tested for their antimicrobial activity; out of them, 19 isolates showed a positive response. They were isolated from 18 different soil samples from different locations in Kuala Lumpur, Malaysia. Modified agar-streak, agar disc diffusion method (ADD) and agar well diffusion method (AWD) methods were used in both primary and secondary screening. Isolation media were applied, without antibiotic integration and pretreatment heat, which stimulated the growth of actinomycete isolates. Antagonistic actinomycetes were identified based on morpho-chemical properties using Probability Identification of Bacteria (PIB) software. Results: Starch casein agar was found to be selective for actinomycetes. The inhibition zone diameters were found to be larger on nutrient agar plates for bacterial targets. Out of 19 actinomycetes with antagonistic activity, 5 actinomycetes were chosen for secondary screening and further identification. Selected criteria’s were based on a strong zone of inhibition against at least four tested bacteria, specifically targeted organisms, E. coli MTCC 740 and S. aureus MTCC 501. Four isolates were tentatively identified as; Streptomyces violaceoniger, Streptomyces antibioticus, Streptomyces atroolivaceus and Streptomyces alboflavus. Conclusions: Four actinomycete isolates of genus Streptomyces proved strong antibiosis activity against two Gram –ve and +ve important bacterial strains.