Regulation of the subpolar flagellum synthesis in Bradyrhizobium diazoefficiens

CAROLINA DARDIS; JUAN IGNACIO QUELAS; FLORENCIA MENGUCCI; ELIAS JAVIER MONGIARDINI; MARÍA JULIA ALTHABEGOITI

Córdoba

Congreso; LII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2016

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Bradyrhizobium diazoefficiensis the soybean nitrogen-fixing symbiont commonly used in inoculant formulations. This α-proteobacterium uses two independent flagellar systems to swim in liquid and viscous media. In our laboratory, we studied thesynthesis and regulation of both flagellar systems, and here we show part of the regulatory cascade of the subpolar flagellum synthesis.Flagellar synthesis occurs in steps, each one controlled by different regulators. This process ensures the appropriate timing of thesynthesis of different components. First, a master regulator initiates the signal cascade, then class II regulators control gene expressionof the intermediate products and class III/IV regulators activate flagellum filament formation, the last product assembled.We presentthe characterization ofB. diazoefficiensmutants in two class II regulatory genes (flbDandfliX) and two class III regulatory genes(flaFandflbT), by measuring the transcription levels of the putative targets controlled by them and also the type of flagellins that theyproduced. Our results suggest that the regulation of the subpolar flagellum synthesis is independent from the lateral flagella and iscontrolled in a cell-cycle manner. These results fit with the model previously described inCaulobacter crescentusbut notwithSalmonellamodel, as was thought in earlier studies.