Role of a new locus (mapB) in the biogenesis of Brucella cell envelope

RUIZ-RANWEZ, V.; ESTEIN, S.M.; BIALER, M.G.; RUSSO, DANIELA M.; SYCZ, G.; ZORREGUIETA, A.

Buenos Aires

Congreso; Reunion Conjunta de Sociedades de Biociencias; 2017

Diez Sociedades de Biociencias de la Argentina: SAIC, SAIB, SAI, SAA, SABiof, SABiol, SAFE, SAFIS, SAH, SAP

ROLE OF A NEW LOCUS (mapB) IN THE BIOGENESIS OF Brucella CELL ENVELOPEBrucella species are gram negative bacteria responsible of a zoonosis called brucellosis. They exhibit unique surface properties which make them furtive pathogens and more resistant to several host defence compounds. We have identified a locus of Brucella suis -mapAB- encoding the TAM machinery, that is proposed to participate in the translocation of autotransporters (ATs) through the outer membrane (OM) in gammaproteobacteria. ∆mapB strain showed enhanced sensitivity to lysozyme, Triton X-100 and polymyxin B, indicating that the cell envelope integrity is compromised. This effect was not due to major differences in the LPS structure or to altered total fatty acid composition. To explore the substrates of TAM in Brucella suis, label free proteomic analysis was performed. Some proteins related to cell division were absent in ∆mapB whole membranes fractions and OMP 25/31 porins were diminished. Regarding to ATs, there was an increase in the expression of 3xFlagBmaB monomeric autotransporter in the ∆mapB strain by western blot. However, BmaB was localized in the OM in both wt and ∆mapB strains. By SEM we found anomalies in the bacterial morphology of ∆mapB, such as more elongated and Y shaped bacteria. In vivo approaches indicated that the number of bacteria recovered from macrophages during the initial stages of infection was reduced in the mutant and it showed an attenuated phenotype in mice. Taken together, these results suggest that MapA/MapB are required for cell envelope biogenesis, probably assisting in the correct insertion of a broader subset of protein substrates, which are important for OM stability, virulence and cell division. Key words: Brucella, TAM, membrane biogenesis, autotransporters.