Several BrRe(CO)3L complexes (where L groups are 2,2'-biquinoline substituted in the 3 and 3' positions) were prepared. Their pseudooctahedralfuc structure was established by using FTIR, UV-vis, and 1H-NMR and confirmed by X-ray analysis. A good correlation between the electrochemical parameters and the MLCT electronic transition was found. The crystalline compound, BrRe(C0)3(3,3'-trimethylene-2,2'-biquinoline) belongs to triclinic space groupPiwitha=9,113(11)A,b= 10.192(4)A,c= 12.825(5)A,ar=73.23(4)0,B=81.30(7)0,andy=66.55(5)0.The volume of the unit cell is 1048(1) A3 with Z = 2. The structure was refined to R = 0.040.

Bacterial two-component regulatory systems (TCS) are common components of complex regulatory networks and cascades. In Sinorhizobium meliloti, the TCS ExoS/ChvI controls exopolysaccharide succinoglycan production and flagellum biosynthesis. Although this system plays a crucial role in establishing the symbiosis between S. meliloti and its host plant, it is not well characterized. Attempts to generate complete loss-of-function mutations in either exoS or chvI in S. meliloti have been unsuccessful; thus, it was previously suggested that exoS or chvI are essential genes for bacterial cell growth. We constructed a chvI mutant by completely deleting the open reading frame encoding this gene. The mutant strain failed to grow on complex medium, exhibited lower tolerance to acidic condition, produced significantly less poly-3-hydroxybutyrate than the wild type, was hypermotile, and exhibited an altered lipopolysaccharide profile. In addition, this mutant was defective in symbiosis with Medicago truncatula and M. sativa (alfalfa), although it induced root hair deformation as efficiently as the wild type. Together, our results demonstrate that ChvI is intimately involved in regulatory networks involving the cell envelope and metabolism; however, its precise role within the regulatory network remains to be determined.

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