Antifungal and antibacterial compounds from Streptomyces strains.

Abstract

Sixteen antibiotic-producing Streptomyces sp. isolated from the North Cyprus soils were evaluated for their ability to inhibit in vitro against six filamentous fungi including human and plant pathogens. One promising strain, designed as KEH23 with strong antifungal activity, was selected for further studies. This isolate was identified as Streptomyces sp. based on a great variety of morphological, cultural, physiological and biochemical characteristics. Its antifungal activity was confirmed in batch culture. In order to standardize the antibiotic production some cultural conditions like different incubation temperatures (20.0, 25.0, 30.0 and 37.0°C), carbon sources (glucose, glycerol, starch and sucrose), pH (6.0, 7.0, 7.5, 8.0 and 9.0) and incubation time in hours (24, 48, 72, 96 and 120) were determined. During fermentation, growth, pH and antibiotic production were monitored at 12 h intervals. Penicillium sp. was most sensitive to the produced compound(s) followed by Candida albicans, Cladosporium oxysporum and Alternaria alternata with an inhibition zone 28.0, 20.0, 16.0 and 15.0 mm, respectively. In addition, antibacterial activity of this strain was determined against human pathogenic bacteria such as Staphylococcus aureus, Klebsiella pneumoniae, Kocuria rhizophila, Escherichia coli, Salmonella typhimurium and methicillin-resistant Staphylococcus aureus (MRSA). The present results indicate that isolate KEH23 is a potential antibiotic producer agent for the biocontrol of plant and human pathogens.