Abstract
A Streptomyces sp. strain named 5K10, isolated from soil samples of Kaziranga National Park, Assam, India was found to secrete an antimicrobial proteinaceous compound, showing in vitro antagonistic effect against some pathogenic bacteria, yeasts, dermatophytes and filamentous fungi. Capacity to produce extracellular antimicrobial substances by the strain 5K10 was assessed by conventional spot inoculation method in agar media against test microorganisms as well as fungal spore germination inhibition assay by microscopic observations. The fermented culture broth with ammonium sulfate precipitation revealed a biologically active proteinaceous compound and molecular weight estimated to be about 14.3 kDa on SDS-PAGE gel. Using Candida albicans MTCC 227 as the indicator strain, antagonistic activity of the proteinaceous compound in the region of the SDS-PAGE gel was confirmed. Bioactivity of the extracellular protein was sensitive to proteinases and partially susceptible to prolonged heat treatment. The results suggest that Streptomyces sp. 5K10 might be an important bioresource of lead molecules for developing antimicrobial agents to control bacterial and fungal infections. Key words: Antifungal activity, extracellular protein, dermatophytes, Streptomyces.
Highlights
Fungi are an extremely diverse group of organisms, with about 250,000 species widely distributed in essentially every ecosystem
The results suggest that Streptomyces sp. 5K10 might be an important bioresource of lead molecules for developing antimicrobial agents to control bacterial and fungal infections
The strain Streptomyces sp. 5K10 showed in vitro antimicrobial activity against test bacteria, pathogenic fungi and dermatophytes with maximum inhibitory effect against C. albicans (Figures 1 and 2)
Summary
Fungi are an extremely diverse group of organisms, with about 250,000 species widely distributed in essentially every ecosystem. Humans and other animals are exposed to fungi from the moment of birth. Only 150-200 or so species are pathogenic to humans and mammals, many non-pathogenic fungi cause allergy symptoms (Chakrabarti, 2005). During the last few decades, the incidence of human systemic fungal infections, especially involving immunocompromised patients, has dramatically increased. Candida spp. accounts for 8-15% of nosocomial blood stream infections and is the fourth most common isolate of patients of intensive care unit (Pfaller and Diekema, 2002). Skin infection due to dermatophytes has become a significant health problem in countries like India and may reach epidemic proportions in areas with high rate of humidity, over population and poor hygienic conditions (Madhavi et al, 2011).
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