Isolation and identification of a novel LCI like antibacterial protein from Bacillus sp. MD-5 reveals its potential application in controlling Staphylococcus aureus in food industry

A novel LCI like antibacterial protein produced by Bacillus sp. MD-5, which was isolated from the Arctic Ocean sediment sample during the sixth Chinese National Arctic Expedition in 2014, was purified and characterized. After saturation of Bacillus sp. MD-5 culture supernatant with ammonium sulfate and separation with ion-exchange chromatography and high performance liquid chromatography (HPLC), an antibacterial protein (MD) was purified. The MD protein was determined to be a novel LCI like antibacterial protein with molecular weight of about 7.0 kDa using liquid chromatograph-mass spectrometer (LC-MS) identification and the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). It displayed antibacterial activity against Staphylococcus aureus at minimum inhibitory concentration (MIC) of 7.33 μg/mL. MD protein possessed high thermostability and wide range of pH tolerance, and had a certain extent of protease, surfactant and metal ion resistance. MD protein was suggested to inhibit the growth of S. aureus through inhibiting peptidoglycan biosynthesis in the view of TEM detection. These results suggested that MD may represent a novel antibacterial protein with potential application in controlling S. aureus in food industry.