甲基营养型芽孢杆菌对疮痂链霉菌的生防潜力

为评价甲基营养型芽孢杆菌SJ80与SJ81对马铃薯疮痂病的生防潜力，以疮痂链霉菌为指示菌，测试了其发酵上清液的理化稳定性，并与咯菌腈、辛菌胺醋酸盐2种农药进行对比，检测其粗提物的生物安全性和抑菌效果。采用牛津杯法抑菌试验，以抑菌直径测试SJ80与SJ81发酵液的最佳发酵时间，发酵上清液经不同温度、紫外照射、pH值及蛋白酶处理后，以抑菌率测试其稳定性，采用MTT法测定粗提物体外急性细胞毒性。结果表明:2种发酵上清液最佳发酵时间为3 d，经121 ℃处理30 min或紫外照射24 h后，抑菌率均高于90%；SJ81在pH=1~13的抑菌率保持在80%以上，有较好稳定性，SJ80在pH=1~11的抑菌趋势与SJ81的相似，在pH=13的抑菌率为0，耐碱性较弱；发酵上清液经碱性蛋白酶与胰蛋白酶处理2 h后，抑菌率均接近100%，对酶处理较稳定。体外急性毒性实验结果显示，SJ80、SJ81对 LO2细胞增殖的半数抑制量（IC50）分别为239，137 mg/L，对PC12细胞的IC50分别为266，161.3 mg/L；在农药的推荐使用量下，咯菌腈和辛菌胺醋酸盐的抑菌率分别为25.46%，0%，对应的细胞活力均低于50%，比发酵液毒性大且抑菌率低。可见，2种拮抗菌发酵上清液理化性质稳定，比农药安全性高，有突出的抑菌优势，具有生防潜力。

Biocontrol Potential of Bacillus methylotrophicus Against Streptomyces scabies

In order to evaluate the biocontrol potential of two Bacillus methylotrophic strains SJ80 and SJ81 against potato common scab,Streptomyces scabies was used as an indicator bacteria to test the physicochemical stability of the fermentation supernatant.Compared with fludioxonil and octylamine acetate to detect the biological safety and antibacterial effect of the fermented crude extract.The Oxford cup method was used to test the bacteriostasis.The bacteriostatic diameter was used to test the optimal fermentation time of SJ80 and SJ81,and the bacteriostatic rate was used to value the stability of the two antagonistic bacteria fermentation broths after treatment with different temperatures,UV irradiation,pH value and protease.The MTT method was used to determine the acute cytotoxicity of crude extracts from SJ80 and SJ81 in vitro.The experimental results showed that the best fermentation time of the two fermentation broths was 3 days,and the antibacterial rates of both were higher than 90% after treatment at 121 ℃ for 30 min or continuous UV irradiation for 24 h.In the pH value range of 1~13,the antibacterial rate of SJ81 remained above 80%,which was similar to that of SJ80.However,SJ80 completly lost its antibacterial activity at pH=13,indicating that the alkali resistance of SJ80 was relatively weak.The fermentation broth was not sensitive to proteinase treatments because the antibacterial rate was close to 100% after treatment with alcalase or trypsin for 2 h.The acute cytotoxicity test in vitro showed that the IC50 of SJ80 and SJ81 for LO2 cells were 239,137 mg/L,and the IC50 for PC12 cells were 266,161.3 mg/L.Under the recommended dosage of pesticides,the bacteriostatic rates of fludioxonil and octylamine acetate were 25.46%,0%,and the corresponding cell viability was less than 50%,which were more toxic than fermentation broth and had lower bacteriostatic rates.Therefore,the two antagonistic bacteria fermentation supernatants had stable physical and chemical properties,and they were safer than pesticides.Meanwhile they had outstanding antibacterial advantages,and had excellent potential for biocontrol.