Study on the Anti-Escherichia coli Activity and Mechanism of Water Extract of Radix isatidis Powder

In order to explore the antibacterial activity and mechanism of the Radix isatidis powder water extract,the effects of the Radix isatidis powder water extract on the morphology and structure of Escherichia coli (E.coli) were tested by scanning electron microscopy and transmission electron microscopy.The effects of the Radix isatidis powder water extract on the conductivity and total leakage rate of E.coli and the content of alkaline phosphatase in the culture medium of the content of protein,DNA and RNA were stained by DAPI to detect the effect of the Radix isatidis powder water extract on the nucleic acid of E.coli,and the effect of the Radix isatidis powder water extract on the metabolism of E.coli in vivo,in vitro,ALT,AST,pyruvic acid and ATP.The results showed that after the Radix isatidis powder water extract acted on E.coli for 10 h,it was observed by SEM that the bacteria appeared to overflow and shrink,the length of the bacteria became shorter obviously,many residues were formed due to breakage,some of them were sunken in the middle and deformed.Under TEM,it was observed that the boundary of the cell wall of E.coli was unclear,the wall membrane was zigzag,deformed and some of the bacteria were broken.The protein content outside the cell was significantly different from that in the blank control group from 8 h (P<0.01), and that in the cell from 4 h (P<0.01). DNA content had no significant difference with blank control group before 12 h (P>0.05), but had significant difference with blank control group from 16 h (P<0.01); RNA content began to decrease at 8 h, and was significantly different from blank control group at 12 h (P<0.05), and was extremely significant from 16 h (P<0.01). There was no significant difference between ALT and AST (P>0.05). The pyruvate content in culture medium and bacteria was higher than that in blank control group, and the difference was very significant from 4 h (P<0.01). The ATP content in the culture medium was significantly different from that in the blank control group (P<0.01), and the ATP content in the cell was significantly different from that in the blank control group from 4 h (P<0.01).In conclusion,the Radix isatidis powder water extract could inhibit the synthesis and metabolism of bacterial genetic material and the content of pyruvate and ATP by destroying the integrity of cell wall and cell membrane.