(1) 中国科学院烟台海岸带研究所

[Objective] c-di-GMP,an important second messenger regulating multiple functions of bacteria,is generally synthesized and hydrolysed by proteins containing GGDEF or EAL domain.In this study,we analyzed the genome-wide GGDEF/EAL domain-containing proteins of Azorhizobium caulinodans ORS571,and selected three GGDEF-EAL composite proteins (AZC_3085,AZC_3226 and AZC_4658) for functional analysis.[Methods] SMART and CLUSTALW were used for prediction and multi-alignment of GGDEF/EAL domain-containing proteins.Mutants were constructed by homologous recombination.Phenotypes including cell motility,exopolysaccharide (EPS) production,biofilm formation and nodulation with legume host were investigated.[Results] There were 37 GGDEF/EAL domain-containing proteins in A.caulinodans ORS571.Mutant Delta4658 showed deficiency in cell motility,while its EPS production and biofilm formation were higher than that of wild type.Mutant Delta4658 showed stronger competitiveness than wild type in competitive nodulation assay.The loss of AZC_4658 led to the increase of intracellular c-di-GMP level.Mutants Delta3085 and Delta3226 did not show obvious difference in comparison with wild type.[Conclusion] The vast number of GGDEF/EAL domain-containing proteins suggested that c-di-GMP may play an important role in signal transduction of ORS571.The GGDEF-EAL composite protein AZC_4658 was involved in cell motility,EPS production,biofilm formation and nodulation of A.caulinodans ORS571.