The oceans cover about 70% of the Earth's surface and harbor most of the planets biodiversity. The marine environment has become a prime resource in search and discovery for novel natural products and biological diversity and marine actinomycetes turn out to be important contributors. The diversity of marine actinomycetes is enormous and has immense scope for the discovery of novel bioactive metabolites. The present study describes the antimicrobial potential of crude extracts of marine Actinomycetes species isolated from Aghanashini, Sharavathi and Kali estuaries of Uttara Kannada district, Karnataka, India. The sediment and water samples were collected from different sites of estuaries and subjected for serial dilution and plating. A total of 43 actinomycetes isolates were obtained on Starch Casein Nitrate Agar and Kusters Agar supplemented with 10% sea water. The isolates were identified as Actinomycetes by morphological and biochemical studies. The results revealed diversity of Actinomycetes with varying spore, aerial and substrate mycelium colours such as white, grey, pink, yellow and black. The colonies formed were discrete, powdery, raised and velvety colonies with brown, yellow and maroon pigmentations. The spore chain morphology studies showed different arrangements like rectus, flexibilis, retinaculum aperatum -open loops, hooks and spira -simple spirals. Primary screening for antimicrobial activity was determined by cross streak method against 16 bacterial isolates among which 07 isolates were gram positive and 09 isolates were gram negative, 02 yeasts viz., Candida albicans and Cryptococcus neoformans and a dermatophyte Trichosporon. The actinomycetes isolates from marine environments have shown to be potent in inhibiting the test bacteria and fungi. Further studies on cytotoxic potential of the actinomycetes isolates on cell lines are under progress.

Western Ghats of India represents one of the global biodiversity hotspots. The present study was carried out to isolate and determine antimicrobial, cytotoxic and antioxidant activity of actinomycetes from soils of different regions of Western Ghats of Shi Karnataka, India. A total of 182 isolates were recovered from 57 soil samples collected at 13 different regions of Western Ghat region of Shivamogga district by serial dilution technique. Out of 182 isolates, 17 isolates were chos determine antimicrobial, cytotoxic and antioxidant activity. Solvent extracts of these isolates exhibited varied antimicrobial potency against Gram positive and Gram negative bacteria, yeasts and molds. Ethyl acetate was found to be best solvent for extraction of bioactive metabolites from most of isolates followed by butanol and hexane. Cytotoxic activity, as evaluated by brine shrimp lethality bioassay, revealed the potency of extracts to cause dose dependent mortality of brine shrimp larvae. Solvent extracts exhibited dose dependent antioxidant activity, as evaluated by DPPH, ABTS, Metal chelating and Ferric reducing assays. Western Ghat actinomycetes appear to be promising resources of bioactive agents and can be exploited industrially. Further studies on recovery of active constituents from solvent extracts and their bioactivity determinations are to be carried out. Abstract Article InformationWestern Ghats of India represents one of the global biodiversity hotspots. The present study was carried out to isolate and determine antimicrobial, cytotoxic and antioxidant activity of actinomycetes from soils of different regions of Western Ghats of Shivamogga district, Karnataka, India. A total of 182 isolates were recovered from 57 soil samples collected at 13 different regions of Western Ghat region of Shivamogga district by serial dilution-plating technique. Out of 182 isolates, 17 isolates were chosen for solvent extraction and to determine antimicrobial, cytotoxic and antioxidant activity. Solvent extracts of these isolates exhibited varied antimicrobial potency against Gram positive and Gram negative bacteria, und to be best solvent for extraction of bioactive metabolites from most of isolates followed by butanol and hexane. Cytotoxic activity, as evaluated by brine shrimp lethality bioassay, revealed the potency of extracts to cause dose brine shrimp larvae. Solvent extracts exhibited dose dependent antioxidant activity, as evaluated by DPPH, ABTS, Metal chelating and Ferric reducing assays. Western Ghat actinomycetes appear to be promising resources of bioactive agents ed industrially. Further studies on recovery of active constituents from solvent extracts and their bioactivity determinations are to be carried out.

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Objective: Western Ghats of Karnataka, India-a biodiversity hotspot is a rich source of microorganisms with undiscovered metabolic capabilities. The upsurge of antibiotic-resistant pathogens has created a greater demand for novel antibiotics. In context to the above a potent soil Streptomyces sp. GOS2 isolated from Agumbe regions of Western Ghats, and its metabolite was assessed and characterized for its antimicrobial spectrum. Methods:The isolation was carried out by soil serial dilution plating on Starch Casein Nitrate agar media (SCN). The obtained isolate was characterized by morphological and biochemical tests. The antimicrobial activity was assessed by well in agar methods against 28 test organisms. The partial characterization of the bioactive metabolite was carried out by thin layer chromatography (TLC) and UV-Visible spectroscopy studies. Results:The isolated GOS2 was observed as a raised powdery colony with grey colored aerial mycelium and media impregnated substrate mycelium. The spore chain was rectus with smooth spore surface. The isolate was gram positive, non-acid fast, positive for catalase, hydrogen sulphide production and starch hydrolysis, negative for casein and gelatin hydrolysis. The carbohydrate fermentation studies showed acid production in dextrose and alkali production in sucrose, lactose, maltose and starch. A prominent antibacterial activity was observed with a zone of inhibition measuring 21-27 mm. The TLC showed a purple spot and UV spectroscopy revealed λ max at 233.2 and 235 nm indicating macrolide group of antibiotics. Conclusion:Western Ghats actinomycetes are a potent source of novel antibiotic molecules.