The Study Of Antibacterial Activity And Mechanism Of Glycinin Basic Peptide Against Staphylococcus Aureus

In this study,the survey of glycinin basic peptide(GBP)and the research method of antibacterial action was recommend.The antibacterial characteristics of GBP against Staphylococcus aureus(S.aureus)was reserhed.The effect of GBP on cell wall,cell membrane and intracellular biomacromolecules of S.aureus were investigated to reveal its antibacterial mechanism.The main experimental results were as follows:(1)The dimeters of inhibition zones of S.aureus treated with different concentration GBP was determined the antibacterial activity of GBP.The minimal inhibitory concentration of GBP on S.aureus was discussed by conventional plate count method.S.aureus cells were treated with a series of GBP concentration.The growth inhibition of GBP on mid-logarithmic-phase cultures of S.aureus was evaluated by spectrophotometer.The results showed that GBP had remarkable antibacterial effects against S.aureus,and the minimal inhibitory concentration(MIC)of GBP was 50 μg/ml.The survival number of S.aureus bacteria was decreased with increasing GBP concentration.The growth curve of S.aureus cells treated with 50 μg/ml GBP at mid-logarithmic-phase had no much inhibition,but the concentration of GBP up to 100 μg/ml had obvious inhibition.(2)In order to reveal the effect of GBP on cells wall of S.aureus cells,the measurement of the OD630 of cells wall,atomic force microscopy(AFM)and release of alkaline phosphatase(OD405)was researched.The result showed that resulte more serious morphological changes as treatment time and GBP concentration increased.The alkaline phosphatase of S.aureus treated with different GBP was released into the medium,and the release level was increase with the increase of GBP concentration and treatment time.GBP could damage the structure of cell walls,and improve the cell alls permeability,causing the leakage of alkaline phosphatase.(3)GBP could disrupt the membrane and increase the permeability of cells membrane in bacteria,and inducted the release of incelluar substance,such as β-galactosidase,nucleotide,proteins and reducing sugar.The release could affect the physiology and biochemical metabolism processes of S.aureus,and the osmotic pressure disequilibrium,hindering the growth of bacteria and even killing bacteria.The release level was increase with the increase of GBP concentration and treatment time.(4)The reduction of respiratory chain dehydrogenase activity caused by GBP might inhibit the normal respiration of cells.Agarose gel electrophoresis and SDS-PAGE demonstrated that contents of DNA and protein in S.aureus cells treated with GBP decreased as treatment time extended.GBP could inhibit biosynthesis of DNA and protein.Besides,gel-retardation experiment exhibited that GBP could bind to DNA.The degree of combination of GBP with DNA became high as GBP concentration increased.