Abstract
Actinomycetes are a gram-positive, filamentous subgroup of bacteria most known for antibiotic producti on. In fact, most of the antibiotics available today ha ve 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 ye t 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 agains t 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 actin omycetes isolates were active against at least one of the test microorganism. Characterization of a selected isolate has led to identification of a unique strai n of actinomycetes (MP 525) showing broad-spectrum antibacterial and antifungal properties. The strain MP 5 25 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 sugges ted that the strain might be producing LLE19085-like antibacterial and a flavone glycoside-l ike antifungal antibiotics, which can be further ex ploited for industrial and biological applications.
Highlights
The phylum Actinobacteria contains several hundred bacterial species that are commonly found in soil, freshwater and marine environments
Potential antibiotic producers were screened against four test microorganisms (Escherichia coli Microbial Type Culture Collection (MTCC) 739, Staphylococcus aureus MTCC 96, Streptomyces lividans TK23 MTCC 4 and Candida albicans MTCC 227)
Screening of single colonies for antimicrobial activity was performed by cross streak method (Waksman and Lechevalier, 1962) using four test microorganisms (Streptomyces lividans TK23 MTCC4, Staphylococcus aureus MTCC 96, Escherichia coli MTCC 739 and Candida albicans MTCC 227)
Summary
The phylum Actinobacteria contains several hundred bacterial species that are commonly found in soil, freshwater and marine environments. Some Actinobacteria are animal and plant pathogens, such as Mycobacterium, Corynebacterium, Nocardia, Rhodococcus and a few species of Streptomyces. These species are gram-positive filamentous bacteria, which produce aerial hyphae and differentiate into chains of spores (Oskay et al, 2004). 70-80% of the commercially available secondary metabolites have been isolated and characterized from several species of actinomycetes (Khanna et al, 2011). These secondary metabolites represent an opulent source of biologically active compounds such as antibiotics, agrochemicals, enzyme, immunosuppressants, antiparasitics and anticancer agents (Berdy, 2005). A mathematical model designed to estimate the number of undiscovered
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