A total of six isolates of Actinomycetes were collected from marine sediments of Andaman Islands. Each isolate was tested against five pathogenic bacteria and also against some pathogenic fungi. Among the six isolates, one of the isolates showed potent activity against all the bacteria and fungi. These isolates appear to produce high anti-fungal and anti-bacterial compounds on potato dextrose agar and nutrient agar medium respectively, by using the agar diffusion method. The potent Actinomycetes were characterized by morphological methods consist of macroscopic and microscopic methods. The mycelium structure, color and arrangement of conidiophores were observed through the oil immersion (100X). Various biochemical tests performed for the identification of potent isolates are as follows: Melanin reaction, H2S production, tyrosine reaction, starch hydrolysis, casein hydrolysis, gelatin hydrolysis, milk coagulation and peptonization, nitrate reduction, temperature range of growth, pH tolerance and cell wall type by comparing all these results with the Bergey’s manual of Determinative Bacteriology and the organisms were identified. All the isolates were identified to belong to the genus Streptomyces. Further purification of the spent medium may gives more activity than the standard antibiotics and also effective against some multidrug resistant pathogens.
Key words: Actinomycetes, Streptomyces, antimicrobial activity, pathogenic bacteria, pathogenic fungi, spent medium, secondary screening test
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