中文摘要：

一个新细菌的第二等的送信人，二度 --(3,5 ) 周期的二聚的 guanosine monophosphate (c-di-GMP ) ，通常被综合或由包含的蛋白质分解了 GGDEF 或 glutamatealanineleucine (EAL ) 领域。因为 c-di-GMP 和他们的基因的 cyclase 或 phosphodiesterase 根据已知的 genomic DNA 序列在几乎所有细菌之中是分布式的，他们经常行动。然而， GGDEF 和 EAL 基因的系统的鉴定在 rhizobia 仍然保持不清楚，与兼容的荚交往到的土壤细菌形成修理氮的小瘤。在这研究， 19 通常认为的 GGDEF 和 EAL 基因在模型根瘤菌被识别， Sinorhizobium meliloti，由生物信息的分析(编码 5 GGDEF 蛋白质和 EAL 双域蛋白质) 。14 基因的空异种通过系统的 plasmid 插入被构造。所有 14 基因异种在最小的中等、有缺点的活动性显示出缺乏的生长，并且 11 基因异种生产了更多的 exopolysaccharide 并且在主人工厂上显示了更少的竞争生节，苜蓿。我们的结果建议 GGDEF 和 EAL 蛋白质可以在 S 的控制起不同作用。meliloti 生理学，尽管他们包含保存催化(GGDEF 或 EAL ) 领域。我们发现也暗示了那 c-di-GMP 可以在在这根瘤菌和它的主人之间的相互作用起一个重要作用种建立有效共生。

英文摘要：

A new bacterial secondary messenger, bis-（3＇,5＇）-cyclic dimeric guanosine monophosphate （c-di-GMP）, is usually synthesized or decomposed by proteins containing GGDEF or glutamate-alanine-leucine （EAL） domain. They often act as cyclase or phosphodiesterase of c-di-GMP and their genes are distributed among almost all bacteria according to known genomic DNA sequences. However, the systematic identification of GGDEF and EAL genes remains unclear in rhizobia, soil bacteria that interact with compatible legumes to form nitrogen-fixing nodules. In this study, 19 putative GGDEF and EAL genes were identified in a model rhizobium, Sinorhizobium meliloti, by bioinformatic analysis （encoding 5 GGDEF proteins, 4 EAL proteins, and 10 GGDEF and EAL double-domain proteins）. Null mutants of 14 genes were constructed through systematic plasmid insertion. AH 14 gene mutants showed deficient growth in minimal medium and defective motility, and 11 gene mutants produced a lot more exopolysaccharide and displayed less competitive nodulation on the host plant, alfalfa. Our results suggested that GGDEF and EAL proteins may play different roles in the control of S. meliloti physiology, although they contain conserved catalytic （GGDEF or EAL） domains. Our finding also implied that c-di-GMP may play an important role in the interactions between this rhizobium and its host plants to establish efficient symbiosis.