Date Published: December 31, 2015
Publisher: Springer Berlin Heidelberg
Author(s): S. Sinimol, A. R. Sarika, A. Jayakumaran Nair.
The diversity of some of the culturable microorganisms associated with marine flora and fauna collected off Vizhinjam and Mulloor coast of South India was evaluated and their bioactive production potential determined. From a total of 24 bacteria, 4 actinomycetes and 8 fungi isolated from diverse marine sources, five bacterial species-BLM3, BSP2, BCS1, BCS4 and BMA6 showed inhibitory activity against at least one of the tested pathogens viz., Klebsiella pneumonia KU1, Pseudomonas aeruginosa VL3, Salmonella enterica typhimurium MTCC 98, Escherichia coli MTCC 40, Micrococcus luteus MTCC 105, Staphylococcus simulans MTCC 3610, Proteus vulgaris MTCC 426, Vibrio fluvialis, Vibrio sp. P3a and Vibrio sp. P3b. The isolated actinomycetes and fungi did not produce significant inhibition zones against the tested pathogens; however, the macroalgal isolated actinomycetes strain AMA1 produced reddish pigment in Starch Casein medium which remained stable till the stationary phase of growth. The marine sediment isolate BCS4, identified as Bacillus sp. showed wide spectrum of activity against the tested Gram positive bacteria, S. simulans MTCC 3610 and Gram negative bacteria, Proteus vulgaris with zone of inhibitions of 25 and 11 mm respectively. Better extraction of the bioactive compound was obtained with ethyl acetate when compared with methanol, benzene and hexane and TLC analysis revealed the presence of an active compound. The 16SrRNA sequencing confirmed the potent strain belong to Bacillus sp. and hence designated Bacillus sp. BCS4.
The increasing antibiotic resistance pose serious concerns in health sector and necessitates seeking natural alternatives. The marine ecosystem being less explored, have prospects for finding novel bioactive producing microbes. Marine microbes represent a distinctive group of organism owing to their immense genetic (Strobel and Daisy 2003) and biochemical diversity (Rusch et al. 2007) and are rich sources of a large variety of bioactive compounds (Debbab et al. 2010). These originate mainly in sediments but they are also present in open oceans in association with other marine organisms (Supriya and Yogesh 2010). Marine invertebrates and plants, in particular, represent an environment rich in microorganisms that produce compounds with bioactive properties including antibacterial, antifungal, antiviral, anticancer, antifouling and antibiofilm activities (Glöckner et al. 2012). The microbial symbionts were been crucial in the discovery of many bioactive compounds reported earlier. The competition among microbes for space and nutrients is one of the driving forces behind the production of precious antibiotics and other useful pharmaceuticals in the marine environment (Thakur et al. 2005b). Microorganisms associated with marine invertebrates are proved to be valuable candidates for drug discovery (Jensen and Fenical 2000; Hentschel et al. 2003; Imada 2004; Thakur et al. 2005a).
The marine ecosystem is less harnessed in terms of developing alternative drugs to antibiotics. The rich diversity, along with extreme physical conditions makes marine environment an ideal source for proving novel drug leads. The coasts, Vizhinjam and Mulloor along the south-west coast of India harbour rich and biodiverse flora and fauna with millions of microorganisms associated with it. When compared to the terrestrial counterparts, these flora and fauna and the marine environment, in general possess novel drugs and other chemically diverse bioactives (Delong 2007). Though the percentage of culturable microbes remains too little, these can provide insights into the characteristics and potency of microbes (Glöckner et al. 2012) thriving in such extreme conditions.