Abstract
Several bacterial cultures were isolated from sponge Halichondria sp., collected from the Gujarat coast of the Indo Pacific region. These bacterial cultures were fermented in the laboratory (100 mL) and the culture filtrate was assayed for antibiotic activity against 16 strains of clinical pathogens. Bacillus sp. (SAB1), the most potent of them and antagonistic to several clinically pathogenic Gram-positive, Gram-negative bacteria and the fungus Aspergillus fumigatus was chosen for further investigation. Analysis of the nucleotide sequence of the 16S rDNA gene of Bacillus sp. SAB1 showed a strong similarity (100%) with the 16S rDNA gene of Bacillus licheniformis HNL09. The bioactive compounds produced by Bacillus licheniformis SAB1 (GenBank accession number: DQ071568) were identified as indole (1), 3-phenylpropionic acid (2) and a dimer 4,4′-oxybis[3-phenylpropionic acid] (3) on the basis of their Fourier Transform Infrared (FTIR), Nuclear Magnetic Resonance (NMR) and Electrospray Ionization Mass Spectrometer (ESI-MS) data. There is a single reference on the natural occurrence of compound 3 from the leaves of a terrestrial herb Aptenia cordifolia in the literature, so to the best of our knowledge, this is a first report of its natural occurrence from a marine source. The recovery of bacterial strains with antimicrobial activity suggests that marine-invertebrates remain a rich source for the isolation of culturable isolates capable of producing novel bioactive secondary metabolites.
Highlights
Sponges are the most primitive of multicelled animals and have existed for more than 800 million years [1]
Mass culture of Bacillus licheniformis SAB1 for chemical characterization led to the identification of three compounds of which two are known and the third one, which though known as metabolite of a terrestrial herb, Aptenia cordifolia, is being reported here for the first time from a marine bacterium
It has been estimated that over 99% of the marine sponge-associated microbes have yet to be cultured in the laboratory with bacteria isolated from the sponges containing diverse Bacillus species being one of the most divergent forms [14]
Summary
Sponges are the most primitive of multicelled animals and have existed for more than 800 million years [1] They are known to produce secondary metabolites which play a decisive ecological role, protecting them against potential invaders, predators or other competitors [2]. Sponge-associated bacteria become a highly potential source for the production of antibiotic compounds. To determine which of these isolated bacteria produced potentially useful antimicrobial substances. Their activity was tested against clinical pathogens and multidrug resistant bacterial strains. Mass culture of Bacillus licheniformis SAB1 for chemical characterization led to the identification of three compounds of which two are known and the third one, which though known as metabolite of a terrestrial herb, Aptenia cordifolia, is being reported here for the first time from a marine bacterium
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