The Study On Antagonism Mechanism Of The Antibiotics JX From Micromonospora Carbonacea JXNU-1 Against Kocuria Rhizophila

The M. carbonacea JXNU-1 was isolated from the Yao Lake farmland soil samples in Nanchang at our laboratory. In the former work of our laboratory, we had found the antibiotics JX produced by the M.carbonacea JXNU-1 hold broad spectrum antibacterial activity. The methods for separation and purification of antibiotics from fermentation broth were established, and chromatography pure antibiotics products were obtained, which indicated that the fermentation liquid contained only a single component of broad-spectrum antibiotics. The antibiotics with the spectral characteristic of absorption could be nucleoside substances by instrumental analysis. The antibiotics JX is a new type of antibiotics and has a good application prospects. The main research contents and results were as follows:(1)The antibacterial activity of antibiotics in vitro was often shown through the minimum inhibition concentration(MIC), the minimal bactericidal concentration(MBC) and the bacteria time-killing curve.The results show that the MIC of the antibiotics JX against K. rhizophila was 3.64 ug/mL and the MBC of the antibiotics JX against K. rhizophila was 7.28 ug/mL. At the same time, time bacteria time-killing curve of antibiotics JX show that after 12 h sterilization on the K. rhizophila rate reached 99.6%. Compared to control group, the K. rhizophila individual varied volume increased obviously under the 1/2 MIC of antibiotics JX. The results indicated that cell division was inhibited when the K. rhizophila was under the 1/2 MIC of antibiotics JX.(2)The fluorescence microscopy and fluorescence spectrophotometer studies manifested that 4'6-diamidino-2-phenylindole(DAPI) could integrate with K. Rhizophila. The results showed that the DNA and RNA content in control and test group was no significant difference. It was seen that the antibiotics JX produced by the M. carbonacea JXNU-1 played no part in the DNA and RNA synthesis of K. rhizophila.(3)It was found that the weight of cell wall was increased with the concentration of antibiotics JX increased under the certain concentration of antibiotics JX. Compared to blank group, the weight of cell wall was increased by 76.5 % when K. rhizophila was cultivated in nutrient broth medium containing a final concentration of MIC antibiotics JX.(4)The concentration of cell protein was determined under the conditions of different concentrations of antibiotics JX. The results show that the content of protein was decreased with the concentration of antibiotics JX increased under the certain concentration of antibiotics JX. The protein content of K. rhizophila was 38.1 mg/g under the MIC of antibiotics and the control group was 18.3 mg/g. The results showed that the protein synthesis of K. rhizophila was obviously inhibited by antibiotics JX produced by the M. carbonacea JXNU-1.(5)We used isobaric tags for relative and absolute quantization(iTRAQ) to analyze the proteomics of K. rhizophila before or after the treatment of antibiotics. Totally 1780 proteins were identified, and the 149 proteins with their expression changed, including 106 proteins up-regulated(ratio?1.2 p-value ?0.05)and 43 proteins down-regulated(ratio?0.833 p-value ?0.05). Under the action of the antibiotics JX, the expression of Mur G enzyme involved in the biosynthesis of peptidoglycan was up-regulated. However, the expression of EF-P factor involved in the synthesis of protein was down-regulated.The study could provid the basic data for explore the secrets about antimicrobial mechanisms of the antibiotics JX from M. carbonacea JXNU-1.