BtaE and BtaF: two members of the trimeric autotransporter family involved in adhesion of Brucella suis to host cells

RUIZ, V.; POSADAS, D.M.; ABDIAN, P.L.; MARTIN, F.A.; AROCENA, G.M.; SIEIRA, R.; ZORREGUIETA, A.

San Miguel de Tucumán

Congreso; VII Congreso Argentino de Microbiología General, SAMIGE del Bicentenario; 2011

Species belonging to the Brucella genera are intracellular pathogens responsible of an endemic disease called brucellosis that causes important economic losses. Even though the intracellular traffic of Brucella was well characterized, the adhesion of Brucella to the host cell was little explored. By phage display we have previously identified a protein from the monomeric autotransporter family (BmaC) that is involved in the attachment of Brucella suis to epithelial cells, probably by interaction with fibronectin. By bioinformatical analysis of the B. suis genome we identified two putative adhesins belonging to the trimeric autotransporter family: BtaE and BtaF. By inmunofluorescence we confirmed that both proteins are exposed on the bacterial surface, as expected for adhesins. We generated clean deletion mutants in the btaE and btaF genes of B. suis 1330. Both mutants showed a marked loss in its ability to attach to HeLa cells. Interestingly, the BtaE mutant had a reduced ability to bind to immobilized hyaluronic acid, while the BtaF showed a reduced attachment not only to hyaluronic acid but to other components of the extracellular matrix (ECM), such as fibronectin and collagen. By heterologous expression of btaE or btaF in a non adherent-non invasive E. coli strain we showed that BtaE confers to E. coli the ability to interact with hialuronic acid while BtaF confers the ability to interact with hyaluronic, collagen and fibronectin. These observations are consistent with the adhesive phenotypes of BtaE and BtaF mutants. Finally, the strain of E. coli expressing btaF showed an enhanced ability to attach to plastic (hydrophobic), but not to glass (hydrophilic). These results suggest that both BtaE and BtaF are involved in the adhesion to eukaryotic cells by a process that could involve the interaction with components of the ECM. Taken together, our observations indicate that adhesion of B. suis to host cells would be mediated by multiple adhesins. Alternatively, different bacterial adhesins may contribute to a differential tissue tropism.