A preliminary study on the antimicrobial activity of marine actinomycetes

Abstract

Aim Marine actinomycetes are considered as an unexplored source of metabolites with novel properties. During the past few years, the studies on marine actinomycetes highlighted their potential as source of nu me rousantibiotios. An experimental study was planned toha rness the potentialof ma rine actinomycetes as asource of bioactive compounds to control plant diseases. Methodology Sediment samples from Thoothukudi coastal ecosystem were collected and analyzed for biological properties. The isolates with different morphological characteristics were selected and about 108 isolates were subjected to cross streak method of screening against fungal cultures like Pyhculariae oryzae, Aspergillus Niger, Fusarium solani, Trichoderma, and Macrophomina sp and bacterial strains like Bacillus cereus, Erwinia carotovora. Serratia sp., Flavobacterium sp and Pseudomonas fluorescens. Solvent extract of isolates producing sign ificantzoneof inhibition were screen edagainst plant pathogens. Results Many isolates produced an inhibition zone of 2 to > 10mm against the fungal and bacterial cultures. The isolate TS3 obtained from TS sediments showed more than 10 mm inhibition zone against Erwinia caratovora, Pyhculariae oryzae. Aspergillus Niger and Trichoderma. The isolates which showed more than 10 mm antifungal and antibacterial activity were selected for further screening. Ehtylacetate extract of RPS5 showed an inhibition zone of 9 to 14 mm and 18 to 22 mm, respectively, against bacterial and fungal pathogens. Similarly, HCS 6 isolates showed an inhibition zone of 9 to 12 mm against bacterial pathogens and 16 to 22 mm inhibition zone, respectively, against fungal pathogens. Interpretation Considering the environmental impacts of chemical fungicides, control of pathogens through biological means helps to overcome the worsening problem caused by chemicals. The solvent extract of RPS 5 and HCS 6 isolates showed significant reduction in the growth of pathogenic organisms, which paves way for commercial exploitation of the isolates to control plant pathogens.