Study On Antibacterial Mechanism And Safety Of The Halostachyscaspica N-butyl Alcohol Extract Against Staphylococcus Aureus

According to research reports that the Halostachyscaspica n-butyl alcohol extract has antibacterial activity against Staphylococcus aureus,and its antibacterial effect is relatively significant,but its antibacterial mechanism has not yet been determined.In this experiment,the antibacterial mechanism of the Halostachyscaspica n-butyl alcohol extract against Staphylococcus aureus was systematically elucidated by studying its cell membrane permeability,cell wall integrity and bacterial metabolic activity.The Halostachyscaspica n-butyl alcohol extract was tested by in vivo safety test in mice,which provided basic theoretical basis for the development and application of Halostachyscaspica n-butyl alcohol extract.The main contents and results of this study are as follows:The minimum inhibitory concentration(MIC)of Halostachyscaspica n-butyl alcohol extractagainst Staphylococcus aureus was 25mg/mL and the minimum bactericidal concentration(MBC)was 50mg/mL by agar double dilution method.Conductivity,leakage of small molecular substances(potassium ions)and large molecular substances(nucleic acids)in the bacterial suspension were determined by conductivity method,visible\spectrophotometry and microplate reader detection methods,reflecting the mechanism of action of Halostachyscaspica n-butyl alcohol extract on Staphylococcus aureus cell membrane.The results showed that when the Halostachyscaspica n-butyl alcohol extract acted on the thallus,the intracellular small molecular substances(potassium ions)and macromolecular substances(nucleic acids)leaked out of the cell,which indicated that the Halostachyscaspica n-butyl alcohol extract could change the permeability of staphylococcus aureus cell membrane.The changes of alkaline phosphatase content,peptidoglycan content and cell wall chemical bonds in the bacterial suspension were determined by micro enzyme labeling method,enzyme linked immunosorbent assay and infrared spectrum detection method,reflecting the mechanism of action of n-butanol extract of Sargassum on the cell wall of Staphylococcus aureus.The results showed that when the n-butanol extract of Salicornia bigelovii Torr acted on the bacteria,alkaline phosphatase in the bacteria leaked to the outside of the cell and had slight influence on the chemical bond of the cell wall,but had no obvious influence on the peptidoglycan content of the cell wall,which indicated that the n-butanol extract of Salicornia bigelovii Torr could destroy the integrity of the cell wall of Staphylococcus aureus.Chemiluminescence detection method and SDS-PAGE gel electrophoresis were used to detect ATP release content and bacterial protein synthesis and expression of Staphylococcus aureus,reflecting the mechanism of action of n-butanol extract from Sargassum on metabolic activity of Staphylococcus aureus.The results showed that the treatment of Staphylococcus aureus with n-butanol extract of Salicornia bigelovii Torr at different concentrations decreased ATP content in the bacterial suspension.Some protein bands were deleted in the thallus added with n-butanol extract of Salicornia bigelovii Torr.This indicated that the n-butanol extract of Salicornia bigelovii Torr can affect the metabolic activity of bacteria.The toxicity of n-butyl alcohol extract from Salicornia bigelovii Torr was reflected by in vivo safety test on mice.The results showed that the mice did not die when the total dose of the n-butyl alcohol extract was 60 g/(kg bw)administered several times in one day,which indicated that the n-butyl alcohol extract of S.salicina was less toxic.