ABSTRACT

This research work was carried out to isolation and characterization of antibiotic producing actinomycetes in rhizosphere environments using the standard microbiological method, crowded plate method, streak plate method and pour plate method. Starch casein agar and Nutrient agar were used for the characterization of the growth organisms and tests such as gram staining, starch hydrolysis, casein hydrolysis, lipid hydrolysis, citrate, methyl red, catalase and indole were carried out. After culturing only 5 out of the 13 isolates (from a total of 25 soil samples) showed visible growth and had antimicrobial activity on selected organisms(Stapylococus aureus, Bacillus subtilis and  Escherichia coli), the total count for the colony forming units ranged from 3.9×106– 5.2×106. The five isolates gotten from this work had four of them from the genus Streptomycetes (denoted as B, F, H and M) and the other from the genus Nocardia (L). Isolate B was active against Escherichia coli with a zone of inhibition measuring 26mm, isolate F, H, L and M were active against Staphylococcus aureus with zones of inhibition measuring 8mm, 9mm16mm and 9mm respectively, while isolate B, F, H, L and M were active against Bacillus subtitis with zones of inhibition measuring 5mm, 11mm, 11mm, 19mm and 7mm respectively. This study shows that Streptomyces are the most prevalent antibiotic producing actinomycetes in the soil. Therefore antibiotics should be taken only when needed to avoid antibiotic resistance by certain organisms and stored at appropriate conditions (temperature and pressure) hence, further purification, elucidation, and characterization are recommended to know the quality and novelty and commercial values of antibiotics.