Isolation and Characterization of Antibiotic Producing Actinomycetes from Mud Nest of Wasps

Abstract

The recent increase in antibiotic resistance demands the discovery of novel antibiotics. Hence, this project was designed to explore novel antibiotic producing Actinomycetes from mud nest of wasps. For this, 9 types of active mud nests of wasp available in Rajshahi, Bangladesh were collected. For each nest, nest material was aseptically homogenized with a 1X saline solution and then diluted homogenate was plated in Actinomycetes Isolation Agar medium to isolate Actinomycetes. Total 27 purified cultures of bacteria were isolated from 9 collected mud nests of wasp. To collect the extract of mud nest, homogenate was filtered and centrifuged. Then, the extracts were assessed for their efficacy to inhibit bacterial growth with disc diffusion method. However, only extract of nest number 9 (N9) showed antimicrobial efficacy against tested bacteria, E. coli. Then antimicrobial efficacy of the 27 isolates was assessed using an agar cross-streak method and disc diffusion method. It was found that among the 27 isolates; only the isolate N9C2 was able to inhibit the growth of studied bacteria, E. coli. Then, 16S rDNA was isolated, amplified and sequenced from the isolate N9C2 for its identification. According to NCBI blast, the highest similarity of sequence (99%) of 16S rDNA of the isolate N9C2 was shown to that of Streptomyces coelescens strain AS 4.1594. Then, the isolate N9C2 was characterized. It was found that the isolate was a gram positive filamentous bacterium. It was found that the isolate N9C2 was resistant to Amoxicillin, Ampicillin and Cephalexin while it was sensitive to Tetracycline, Erythromycin and Ciprofloxacin. It was also found that the isolate N9C2 can grow optimally at pH 7 and at 37ºC. Finally, it can be concluded that mud nests of wasp is a vital source of antibiotic producing Actinomycetes such as Streptomyces coelescens strain AS 4.1594.