Abstract:
Various disease causing microbes have become resistant to antibiotics that are being used for
their treatment. Today, there is renewed interest in finding new novel antibiotics that help cure
diseases caused by drug-resistant pathogenic bacteria. The present study was conducted to
investigate the presence of antibacterial producing actinomycetes from soil samples of Angereb
river bank and evaluate for their antibacterial activities against test pathogenic bacterial strains.
A total 10 actinomycetes isolates were recovered from hither and offside of Angereb River bank
soil. Out of the 10 actinomycetes isolates screened for antibacterial activities, 5 (50%) isolates
showed activities against the tested pathogenic bacteria. In order to extract the active compound
from isolates, submerged state fermentation was carried out on five isolates and the former was
extracted by using methanol and acetone solvents. The antibacterial activity of the crude extract
was studied by using Agar well diffusion assays. The crude extracts obtained from isolates (S01,
S14, and S19) showed variations in spectrum activity against test pathogenic bacteria. Methanol
crude extract of isolate S14 showed a wider spectrum of antibacterial activities against Gram
positive and Gram negative bacteria (Escherichia coli). Larger inhibition diameter zone was
recorded by acetone crude extract of isolate S19 (31mm) against K.pneumonea. The resistance
test pathogen bacteria are E.coli and P.aerugenosa against all acetone and methanol crude
extracts of isolates, respectively. The most sensitive one was K.pneumonea that was inhibited by
S01, S14 and S19 isolates crude extracts, with varying inhibition zone diameter. The potential
isolates were characterized by cultural, morphological, and biochemical characteristics and found
to be classified under the genus Streptomycetes. All taken together, Angereb river bank soil is a
potential sources of antibiotic producing actinomycetes isolates, and the crude extract obtained
from isolate S14 demonstrate broad spectrum with a remarkable antibacterial activity. However,
further investigations on the potential isolates should be required to fully realize their
antibacterial property on different test microorganisms, efforts have to be establishing towards
molecular characterization of these isolates, and on purification of the active compound from
these potential isolates.
