Abstract:
Actinomycetes are gram positive bacteria that widely serve as source of novel antimicrobial
substance. This study was designed to evaluate antimicrobial activities of actinomycetes isolated
from soil in Bada Buna. The study was conducted at Bada buna forest. Rhizospehre soil of
indigenous plants of natural Bada Buna natural forest were selected purposively following
purposive sampling technique. Then, twenty five soil samples were collected. For laboratory
analysis, ten gram of each soil sample was taken in sterilized Erlenmeyer flask containing 90ml
of normal saline solution (0.85%) and shaken on rotatory shaker (160rpm) for about5 minutes.
The pure cultures were screened for antimicrobial activities by inoculating the pure culture into
starch casein broth for fourteen days after which it was centrifuged at 10,000 rpm for 20
minutes. The supernatant was check for antimicrobial activities using disc diffusion and agar
well diffusion method. In the present study, 60 actinomycetes were isolated out of which twelve
(20%) showed antimicrobial activity against one or more human pathogenic test bacteria and
fungus. Among a total of twelve isolates 6 (50%) actinomycetes showed antimicrobial activities
both on gram positive and gram negative bacteria,5(41.66%) of the isolates showed
antimicrobial activities against only gram negative bacteria and 1(8.33%) the isolate showed
antimicrobial activities against gram positive bacteria. Four (33.3%) isolates showed
antimicrobial activities on C.albicans (ATCC14053).Of the twelve isolates that displayed
antimicrobial activity, 6 isolates were further screened for submerged fermentation based on
their activities. Except isolate AC10, all the crude extracts of isolate exhibited antimicrobial
activity against all the test organisms during secondary screening process. The isolates were
identified and characterized by morphological, physiological, and biochemical characteristics.
From the present study it could be conclude that rhizosphere soil could be potential source of
antibiotic producing actinomycetes. Further work needs to carried out in details and the isolates
identified up to species level by using molecular characterization.
