ANTIMICROBIAL ACTIVITY OF A STREPTOMYCETE ISOLATE FROM WHEAT FARM SOIL IN MAU FOREST COMPLEX, KENYA

Abstract

The study involved isolation of Streptomyces spp. from the soil of various sites in the Mau Forest Complex in Kenya. The isolates were screened for antimicrobial activity against selected bacterial and fungal plant pathogens including; Fusarium moniliforme, Ascochyta rabiei, Erwinia carotovora, Xanthomonas campestris pv. campestris, Pseudomonas savastonoi pv. phaseolicola and reference cultures which were: Staphylococcus aureus ATCC 25923; Escherichia coli ATCC 25922; Pseudomonas aeruginosa ATCC 27853 and Bacillus subtilis ATCC 6633. One isolate from a wheat farm designated as WHF2B16 tested positive as a Streptomyces species through cultural, morphological, biochemical and molecular characterization. It was found to have antimicrobial activity against the fungal pathogens with a zone of inhibition >20 mm; one plant bacterial pathogen i.e. Pseudomonas savastonoi pv. phaseolicola with an inhibition zone of 15.5 ± 1.2 mm and was active against the Gram positive bacteria i.e. Bacillus subtilis and Staphylococcus aureus. Ethyl acetate extracts compared to culture filtrates of the isolate were found to produce significantly higher growth inhibitory effects in the test microorganisms in a t test (t-value P > 0.05). The isolate was further subjected to 16S RNA analysis and confirmed to be a Streptomyces species assigned as Streptomyces mau 1 (Accession No. KR780774) from the NCBI database. This study has revealed that a streptomycete from a wheat farm in the Mau Complex in Kenya has the potential to be used as an antifungal and antibacterial agent.