Functional Characterization of the tolC gene of Brucella suis in heterologous host

DIANA POSADAS; MATÍAS KINZURIK; FERNANDO MARTÍN; M. VICTORIA DELPINO; ELEONORA CAMPOS; CARLOS A. FOSSATI; PABLO C. BALDI; ANGELES ZORREGUIETA

Posadas, Misiones, Argentina

Congreso; XL Reunión de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2004

Abstract Outer membrane proteins of the TolC family have been implicated in several functions including efflux of toxic compounds and protein secretion. In the alpha-2 group of proteobacteria, like in Rhizobium spp. and Brucella spp. the role of this protein family remains unknown. Only one member of the TolC family was identified by Blast search in the Brucella suis genome. The tolCb gene was cloned and expressed in heterologous bacteria.  The hemolysin A secretion defect of an E. coli tolC mutant was weakly complemented by tolCb.  We also intend to rescue the drug hypersensitive phenotype of the E. coli tolC mutant. No complementation of Nalidixic acid susceptibility of the tolC mutant was observed. A Rhizobium  leguminosarum mutant in a gene of the tolC family (nodT) was previously isolated. However, no clear phenotype was associated with mutation in nodT. Interestingly, we found that the nodT mutant was unable to grow in minimal medium and growth in a rich medium was consistently low compared with the wild type. In addition, the extracellular protein profile of the nodT mutant was altered.  The tolCb gene was able to restore growth on rich medium, slightly complemented growth on minimal medium and considerably restored the extracellular protein profile of the nodT mutant.  These observations suggest a more crucial physiological role for proteins of the TolC family in bacteria of the Rhizobiaceae group.