Isolation and characterization of actinomycetes from marine soil

Abstract

Four different actinomycetes were obtained from the sampling sites. The isolate AA1 isolated from Puducherry beach exhibited good antibacterial activity on primary screening when compared to the others and hence was chosen for further study. The isolate AA1 was Gram positive with smooth surface morphology and the spore chain morphology showed them to be simple rectus. When the isolate was grown on different media the ariel mycelia was mostly white while the substrate was cream/white. It was able to grow at a pH of 7 at 30°C and tolerate 7% NaCl. Maltose, lactose and xylose was used as the sole carbon source. The crude ethyl acetate extract of AA1 showed antibacterial activity against E.coli (9mm), S.aureus (7.5mm), P.mirabilis (7.7mm), P.aeruginosa (7mm) and K.pneumoniae (4.5mm) at a concentration of 3.5mg/ml. MIC of the crude extract of AA1 was 0.531mg/ml for E.coli and P.aeruginosa, 1.062mg/ml for S.aureus, 0.265mg/ml for P.mirabilis, and 2.125mg/ml for K.pneumoniae. The FT-IR Spectrum of the crude extract showed characteristic peaks at 3290.56cm-1, 1635.64cm-1 and 1016.49cm-1 corresponding to the following functional group such as alcohol (O-H), Alkene (C=C), Ether (C-O) respectively. The 16S rRNA gene sequences of the isolate AA1 revealed 100% similarity to Streptomyces lincolnensis. The restriction sites prediction of the 16SrRNA gene of Streptomyces lincolnensis showed restriction sites for Eco53KI, Bsr I, Hae II, Eco RV, EcoRI, EagI, Hinc II etc. The restriction site analysis showed GC content of 59% and AT content of 41%.