Antimicrobial Activity of Actinomycetes Isolated from Paya Maga, Sarawak

A study was carried out to evaluate the antimicrobial activity of 51 actinomycetes strains isolated from environmental samples collected during an expedition at Paya Maga, located in Ulu Trusan, Lawas, Sarawak. These actinomycetes strains were isolated from 20 soil and 15 plant samples. Their ability to inhibit the growth of Gram positive bacteria (Staphylococcus aureus, Micrococcus luteus), Gram negative bacteria (Escherichia coli) and yeast (Saccharomyces cerevisiae) were tested by using co-culture method. Twenty five percent of the isolates (13 out of 51) were active against at least one bacteria or one yeast standard strain while 18 (35%) were active against at least two standard strains, indicating broad spectrum activities. The results also showed that 23% (7 strains) of the positive isolates with single or broad spectrum activities were able to show better result in comparison to 100 mg/L of Chloramphenicol and Nystatin used (by forming inhibition zone more than 20 mm in diameter). The 31 inhibitory strains were sequenced and partial 16S rDNA sequences were derived for taxonomic identification. The majority of these strains (27 out of 31) belong to the family of Streptomycetaceae, followed by 2 strains from Streptosporangiaceae and 1 strain each from Nocardiaceae and Pseudonocardiaceae. Sixteen of the isolates can only be classified up to the genus level so they are potentially novel species which are targets for further study to isolate antimicrobial agents.