The Ornithine Lipid of Brucella abortus and its role in physiology and virulence

BUKATA L; MARCORA MS; CARRILLO C; UGALDE R; COMERCI DJ

San Miguel de Tucumán, Argentina

Congreso; XLV Reunión Anual de la Sociedad Argentina de Bioquímica (SAIB); 2009

SAIB

Title: The Ornithine Lipid of Brucella abortus and its role in physiology and virulence Authors: Bukata, Lucas1; Marcora, María S.2; Carrillo, Carolina2,3; Ugalde, Rodolfo A.1; Comerci, Diego J. 1 1IIB-INTECH, Universidad de San Martín; 2 Fundación Instituto Leloir; 3QB-FCEN, UBA Abstract: The main cell envelope (CE) lipids from Brucella abortus are PC, PE and the aminolipid OL (25-30% of each one). The genes olsB and olsA are involved in the two-step reaction that converts ornithine in OL. In order to understand the role that OL plays in the physiology and virulence of this pathogen, the B. abortus genes were identified and disrupted. B. abortus olsB (Ba olsB) and Ba olsA mutants are unable to synthesize OL whereas the latter accumulate the intermediate lyso-OL (LOL). Absence of OL does not affect viability, but the mutants display several phenotypic traits such as an increased bacterial growth rate under nitrogen deprived medium, membrane proteome alterations and reduced virulence in an intragastric mice infection model. Remarkably, the Ba olsB strain over-expressed a response regulator belonging to the NtrXY two-component system, which is involved in nitrogen metabolism. Some of these features could be explained by the increased polyamine synthesis observed in the absence of OL, which is a consequence of the augmented supply of ornithine. The structural similarity of OL with the Lipid A suggests that it could exert some immunomodulatory effect on the immune system. Indeed, mice splenocytes treated with OL were unable to proliferate upon stimulation with E. coli LPS. Altogether, these results suggest that OL is implicated in the virulence performance of Brucella.