Isolation of Antimicrobial Producing Actinomycetes from Indigenous Microhabitats.

Abstract

Unusual microhabitats in different locations present opportunities for the bio-prospecting of actinomycetes with high antimicrobial producing potentials. A total of 113 actinomycetes from specific indigenous microhabitats were isolated and screened for their antimicrobial activity against selected test organisms. The earthworm castings, forest litter, and domestic dumpsite sites, respectively, accounted for approximately 24.78%, 19.47%, and 18.5% of the total number of isolates recovered. The preliminary antagonism assay using the perpendicular streak method yielded four isolates that showed high antimicrobial activity and broad spectrum activity against test bacteria or fungi. These isolates showed excellent growth and sporulation on milk agar and starch casein agar, and the micro-morphological characterization of the isolates revealed the presence of spore-bearing aerial hyphae. Bioactive extracts from DS15 and EC5, at 125 mg/mL, had respective zones of inhibition measuring 20.7 ± 0.6 and 33.0 ± 1.0 against multidrug resistant Escherichia coli (clinical isolate) and Salmonella typhi (ATCC 2923) respectively. Bioactive extracts from EC1 and EC9, at 125 mg/mL, show respective zones of inhibition measuring 18.7 ± 1.2 and 16.7 ± 1.2 against Candida albicans (ATCC 10231) and C. glabrata (ATCC 22018) respectively. This study reinforces the evidence that unique and unusual microhabitats, in different geographical locations, present an excellent opportunity for the bio prospecting of actinomycetes with high antimicrobial producing potentials. Furthermore, it shows that the indigenous antagonistic actinomycete isolates exhibited potent antimicrobial activity against test bacteria and fungi employed in the in-vitro antimicrobial assays.