中慢生型天山根瘤菌胞外多糖相关基因exo5及其在根毛吸附和生物膜形成中作用的研究

Function of Mesorhizobium tianshanense Exopolysaccharide Gene exo5 in Root-Hair Adherence and Biofilm Formation

用质粒pKGL 3上的转座子随机插入失活的方法得到两个中慢生型天山根瘤菌胞外多糖缺失菌株,并通过随机引物PCR的方法确定了转座子插入的基因位点,该基因与豌豆根瘤菌的UDP-葡萄糖脱氢酶基因有高度的同源性。根毛吸附实验发现该基因缺失,导致胞外多糖缺失突变菌株在其宿主植物甘草上的根毛吸附量大大降低,同时生物膜的形成实验发现中慢生型天山根瘤菌的exo5菌株不能像野生型菌株一样形成丰富的生物膜,也从侧面证明了根毛吸附实验的结果,初步推测胞外多糖可能通过影响中慢生型天山根瘤菌的根毛吸附过程来影响其与豆科植物的共生固氮。

Two strains of exopolysaccharide defective mutants （ZJ4,ZJ6） were screened out of transposon mutant libraries. Arbitrary PCR was used to get short chromosomal DNA fragments flanking transposon ends. Sequence analysis of their arbitrary PCR products indicated the transposon was inserted into the gene homologous to the UDP-glucose dehydrogenase in the published Rhizobium leguminosarum strain RBL5523 genomes. The efficiency of root-hair attachment of ZJ0, ZJ4 and ZJ6 suggests that exoplysaccharide may negatively regulate the bacterial root-hair adherence process. In addition, the mutants would not form biofilm like wild ones.