Analysis Of Antibacterial Mechanism Of Berberine Against Xanthomonas Oryzae Pv.Oryzicola

Berberine,a kind of quaternary isoquinoline alkaloids,is usually used as an antibiotic drug.Recently,berberine was found to be a potential pesticide.Berberine could inhibited the growth of Xanthomonas oryzae pv.oryzicola(Xoc)in our early experiments.However,our knowledge of the antibacterial mechanism of berberine against Xoc still remains unknow now.In this study,we investigated the mechanism of berberine against Xoc in cells,biochemical and molecular.The main results are as follows.1.The EC50 of berberine against Xoc was 1.72μg/mL,and the MIC and MBC of berberine on Xoc was 15 and 30μg/mL,respectively.Berberine could inhibit the normal growth of Xoc,and also reduce pathogenicity of Xoc.2.The morphological observation of Xoc under electron microscope showed that the shape and structure of cell treated with berberine were abnormal.Berberine not only destroyed the cell wall but also change the membrane permeability of cells,and the conductivity of the pathogen culture liquid.After treatment with berberine,electrolyte and macromolecules leaked out from cells,and the activity of lactate dehydrogenase and β-galactosidase in the cells culture liquid increased.3.After treatment with berberine at the concentration of 15μg/mL for 240 min,the cell surface hydrophobicity was significantly lower than that of the control group.Furthermore,berberine could also inhibite the formation of biofilm.4.Berberine did not effect on the quantity of exopolysaccharides of the pathogen,but could obviously reduce the content of cellulase and amylase.5.After treatment with berberine at the concentration of 15μg/mL,berberine could cause the accumulation of pyruvate,and their yield were about 4 times as hight as in the control.Meanwhile,berberine could inhibit the activity of malate dehydrogenase(MDH),which related with cell respiratory.And the higher the concentration,the inhibition became more evident.6.To further clarify the function of berberine on Xoc,strand-specific RNA sequencing analysis of wild-type strain and the berberine treatment strain was performed.After compare with the control strain,there are 2568 difference expressed genes in the strains treated with berberine.And functions of these differentially expressed genes related to physiological metabolism,cell wall and cell membrane synthesis,two-component element and pathogenicity of bacteria.7.The present study suggests that berberine could destruct cellular structure and function,change the permeability of cell membranes,inhibit the biosynthesis of bacterial biofilm and interfere with normal physiological metabolism of Xoc.