Identification and Characterization of Antibiotic-Producing Actinomycetes Isolates

Actinomycetes are a gram-positive, filamentous subgroup of bacteria most known for antibiotic production. In fact, most of the antibiotics available today have originated from actinomycetes, namely from the genus Streptomyces. Novel bacteria with antimicrobial activities have been discovered from bacterial screen studies for decades and there is still much more yet to be unearthed. One hundred seventy five strains of actinomycetes were isolated from 38 different soil samples from different locations in Patna, India. Potential antibiotic producers were screened against four test microorganisms (Escherichia coli MTCC 739, Staphylococcus aureus MTCC 96, Streptomyces lividans TK23 MTCC 4 and Candida albicans MTCC 227). The bioassay revealed that about 26% of actinomycetes isolates were active against at least one of the test microorganism. Characterization of a selected isolate has led to identification of a unique strain of actinomycetes (MP 525) showing broad-spectrum antibacterial and antifungal properties. The strain MP 525 has been morphologically characterized as Streptomyces sp. and deposited at MTCC, Chandigarh, India with accession number 8723. The 16S rRNA gene of the strain Streptomyces sp. US7 MTCC 8723 was sequenced and the DNA sequence was deposited at NCBI, Bethesda (GenBank accession. No. HQ659005). On the basis of λmax values of culture filtrates, it has been suggested that the strain might be producing LL-E19085-like antibacterial and a flavone glycoside-like antifungal antibiotics, which can be further exploited for industrial and biological applications.