Frontiers in Marine Science (Jun 2014)
Extracellular compounds from marine bacteria <i>Shewanella</i> sp. with high biotechnological potential.
Abstract
Recently, marine bacteria have received great attention for the search of biologically active substances. As they are continuously competing for space and nutrients they produce a variety of secondary metabolites which inhibit the settlement of potential competitors such as fouling bacteria, invertebrates or larvae. This harsh environment plays a crucial role in the evolution of marine microorganisms making them excellent candidates for the search of bioactive compounds. In this work, the extracellular compounds of Shewanella sp., recently identified as Bifurcaria bifurcata epiphytic bacteria, were evaluated for their antimicrobial and antioxidant potential. Shewanella sp. was grown in Marine Broth during three days in which point the bacteria was centrifuged and the supernatant collected and concentrated for further screening. The antimicrobial potential was evaluated against four model microorganisms: Escherichia coli (ATCC 25922); Staphylococcus aureus (ATCC 25923); Saccharomyces cerevisiae (ATCC 9763) and Bacillus subtilis (ATCC 6633). The ability of extracellular compounds to inhibit microorganism’s growth was accompanied by optical density at 600 nm and the results were expressed as percentage of control. All the tests were performed at 1 mg/ml. The antioxidant activity was evaluated by both, the quantification of the total phenolic content (TPC) and by the evaluation of the DPPH radical scavenging activity. i>Shewanella sp. revealed to produce compounds with high antimicrobial activity against all studied microorganisms, namely with 63.8±3.36% of inhibition against B. subtilis; 60.9±8.64% against S. cerevisiae; 50.66±6.7% against S. aureus and 41.86±2.33% against E. coli. Regarding the antioxidant activity, the supernatant reveal to contain compounds with some ability to scavenge the DPPH radical at 1mg/ml, with a reduction of 29.85±1.68% of control and a total phenolic content of 0.3 mg gallic acid equivalent/g of extract. The extracellular compounds of Shewanella sp. reveal to be a very promising source for antimicrobial compounds that can have further biotechnological application; moreover the extraction method offers important advantages: is simple, sustainable and environmentally friendly. #Carina Marques and Susete Pinteus contributed equally to this work.
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