Bioperspective of actinomycetes isolates from coastal soils: A new source of antimicrobial producers

Abstract

Forty five soil samples were collected from four coastal islands on the east coast of Thailand: Chang, Hwai, Lao-yanai in Trat Province and Pai Islands in Chonburi Province. On 3 isolating media, Actinomycetes Isolation Agar, Starch Casein Agar and Glucose Asparagine Agar, 495 isolates of actinomycetes were found. Preliminary test to search for antimicrobial activity was done with Bacillus subtilis TISTR 008, Staphylococcus aureus TISTR 885, Staphylococus aureus TISTR 517 (ATCC 25923), Micrococcus luteus TISTR 884 and Pseudomonas aeruginosa TISTR 781 and Escherichia coli TISTR 887 (ATCC 25922). Fifty-eight actinomycetes were found to be antimicrobial-producing strains. From the morphological determination, cell wall diaminopimelic acid and sugars in whole-cell hydrolysate studies, among the 58 strains, Streptomyces sp. and Actinomadura sp. were the predominant genera. The other antibiotic active strains were Micromonospora sp., Microbispora sp., Nocardia sp., Pseudonocardia sp., Saccharomonospora sp., Streptoalloteichus sp. and Streptoverticillium sp. Most of them could inhibit gram-positive bacteria, especially M. luteus TISTR 884, and 8 strains (4 strains of Actinomadura, 2 strains of Micromonospora, 1 strain of Microbispora, and 1 strain of Streptomyces) could inhibit both gram-positive and gram-negative bacteria.