THE ANIONIC CHARACTER OF BRUCELLA ABORTUS CYCLIC GLUCAN IS REQUIRED FOR HYPO-OSMOTIC ADAPTATION

ROSET, M.S.; CIOCCHINI, A.E.; UGALDE, R.A. ; IÑÓN DE IANNINO, N.

Rosario, Santa Fe, Argentina

Congreso; XLII Reunion Anual de la Sociedad Argentina de Investigaciones en Bioquimica y Biologia Molecular (SAIB 2006); 2006

Sociedad Argentina de Investigaciones en Bioquimica y Biologia Molecular (SAIB)

Large amounts of periplasmic glucans are found in the periplasmic space of Proteobacteria. Depending on the species considered periplasmic glucan could be modified to various extents by a variety of substituents; however the role attributed to these substituents remains unclear. The Brucella abortuscyclic b-1,2-glucan virulence factor is substituted with O-ester succinyl residues, which confer on the cyclic glucan an anionic character. In a previous work, we demonstrated that B. abortus cyclic b-1,2-glucan succinylation is not required for virulence. Data presented here support a role for anionic substituents of cyclic glucan in hypo-osmotic adaptation. First, we observed that the osmolarity affects the substitution of cyclic b-1,2-glucan, with the highest degree of substitution reached when the cells were grown in a low osmolarity medium. Second, mutants in synthesis (cgs), transport (cgt) and modification (cgm) of cyclic b-1,2-glucan were impaired for growth under low osmolarity conditions. Third, raising the osmolarity of the medium with the addition of ionic or nonionic compounds can restore growth of the cyclic b-1,2-glucan mutants. Moreover, cgm mutant strain harboring a S. meliloti phosphoglicerol transferase is able to restore the cgm mutant grows. This is the first report, in which the role of anionic substituents of cyclic glucan was assigned.