Antimicrobial and cytotoxic activity of pigmented Streptomyces spp. culture extracts

Abstract

BACKGROUND Pigments from microbial origin have promising applications in food, cosmetics, textiles and therapeutics. Compared to other natural sources pigments from bacteria are more stable, safer, and could be cheaper to produce and extract. Bacterial genus Streptomyces has been known as a source of biologicaly active pigments that exhibit several effects such as antimicrobial and cytotoxic. OBJECTIVES The aim of this study was the isolation of pigment-producing Streptomyces strain from soil, optimization of growth parametres for pigment production and evaluation of antimicrobial and cytotoxic activity of extracted bacterial pigments. METHODS Isolation and characterization of pigment-producing Streptomyces strain from soil was done following the standard microbiological protocol, using four different growth media. The pigments were extracted by solvent extraction using ethyl acetate. Antimicrobial activity was analyzed using the disc diffusion test. Cytotoxic activity was tested on the HaCaT cell line following the standard protocol. RESULTS Extraction of pigments by solvent extraction resulted in crude pigment extracts with antimicrobial activities. In total pigments from 14 bacterial strains have been extracted. Antimicrobial activity was evident on Gram + bacteria Staphylococcus aureus (6 mm of inhibition zone at concentration 8.4 μg/ml and 4 mm of inhibition zone at concentration 1.1 μg/ml) as well as on the fungus Candida albicans (4 mm of inhibition zone at concentration 13 μg/ml). Pigments showed dose-dependent inhibiton of proliferation of HaCaT cells, with the lowest concentration at 25 μg/ml.