马铃薯根系分泌物及氨基酸对萎缩芽孢杆菌QHZ3趋化成膜的影响

Effects of potato root exudates and amino acids on the chemotaxis and biofilm formation of Bacillus atrophicus QHZ3

通过土培收集、硅烷衍生化分离、气质联用鉴定马铃薯苗期、现蕾期及盛花期根系分泌物的主要成分,并采用半固体平板法、类毛细管法和结晶紫染色法比较观察马铃薯不同生育时期根系分泌物及氨基酸对萎缩芽孢杆菌QHZ3趋化成膜的影响,以揭示菌株QHZ3在马铃薯根际的定殖机制。马铃薯根系分泌物鉴定中发现了5种氨基酸:脯氨酸、甘氨酸、天冬氨酸、苯丙氨酸和酪氨酸。定性试验显示,马铃薯不同生育时期的根系分泌物和除脯氨酸之外的其他4种氨基酸均对菌株QHZ3具有显著的正趋化作用,并以甘氨酸的作用最强,其趋化圈直径(6.40 cm)是对照(3.48 cm)的1.84倍;定量试验结果表明,根系分泌物(120μg·mL^(-1)和240μg·mL^(-1))、甘氨酸(10~50μmol·L^(-1))、天冬氨酸(50~75μmol·L^(-1))和苯丙氨酸(25~50μmol·L^(-1))均对菌株QHZ3有显著正趋化作用,尤其以25μmol·L^(-1)的甘氨酸趋化性指数最大,其毛细管中细菌数量(5.13×10^(5) CFU·mL^(-1))达到对照组(1.53×10^(5) CFU·mL^(-1))的3.3倍;结晶紫染色法显示,现蕾期和盛花期根系分泌物以及甘氨酸(25~100μmol·L^(-1))、脯氨酸(75~100μmol·L^(-1))和苯丙氨酸(25~100μmol·L^(-1))均对菌株QHZ3生物膜的形成有显著促进作用。根系分泌物和氨基酸均对菌株QHZ3在马铃薯根际趋化成膜具有促进作用,但5种氨基酸的作用各不相同,其中天冬氨酸和酪氨酸显著影响菌株的趋化作用,脯氨酸显著影响了菌株生物膜的形成,而甘氨酸和苯丙氨酸则对菌株的趋化和成膜兼具显著效果。

By soil culture collection,silane derivatization separation,the main components of potato root exudates were identified by gas chromatography-mass spectrometry(GC-MS)at seedling stage,squaring stage and anthesis stage.Semisolid plate,capillary-like test and crystal violet staining method were used to compare the effects of root exudates and different amino acids on chemotaxis and biofilm formation of Bacillus atrophaeus QHZ3 at different growth stages of potatoto,in order to reveal the colonization mechanism of Bacillus atrophaeus QHZ3 in potato rhizosphere.Five amino acids were identified in potato root exudates:proline,glycine,aspartic acid,phenylalanine and tyrosine.Qualitative tests showed that root exudates from different growth stages of potato and other four amino acids except proline had significant positive chemotactic effects on strain QHZ3,and glycine had the strongest effect,and its chemotactic circle diameter(6.40cm)was 1.84 times that of the control(3.48 cm).The results of quantitative test showed that root exudates(120μg·mL^(-1) and 240μg·mL^(-1)),glycine(10~50μmol·L^(-1)),aspartic acid(50~75μmol·L^(-1))and phenylalanine(25~50μmol·L^(-1))all had significant positive chemotactic effects on strain QHZ3,especially with 25μmol·L^(-1) glycine,the chemotaxis index was the highest,and the number of bacteria in the capillary(5.13×10^(5) CFU·mL^(-1))was 3.3 times higher than that in the control group(1.53×10^(5) CFU·mL^(-1)).Crystal violet staining showed that root exudates,glycine(25~100μmol·L^(-1)),proline(75~100μmol·L^(-1))and phenylalanine(25~100μmol·L^(-1))significantly promoted the formation of biofilm in strain QHZ3.Both root exudates and amino acids promoted the chemotaxis and film formation of strain QHZ3 in the potato rhizosphere,but the effects of the five amino acids were different.Among them,aspartic acid and tyrosine had significant effects on the chemotaxis of strain QHZ3,and proline significantly affected the biofilm formation of the strain,while glycine and phenylalanine had significant effects on the chemotaxis and biofilm formation.