RESUMEN
Recently we identified a bacterial factor (BimA) required for actin-based motility of Burkholderia pseudomallei. Here we report that Burkholderia mallei and Burkholderia thailandensis are capable of actin-based motility in J774.2 cells and that BimA homologs of these bacteria can restore the actin-based motility defect of a B. pseudomallei bimA mutant. While the BimA homologs differ in their amino-terminal sequence, they interact directly with actin in vitro and vary in their ability to bind Arp3.
Asunto(s)
Burkholderia/genética , Burkholderia/fisiología , Prueba de Complementación Genética , Proteínas de Microfilamentos/genética , Proteína 3 Relacionada con la Actina/metabolismo , Secuencia de Aminoácidos , Animales , Proteínas Bacterianas/genética , Proteínas Bacterianas/fisiología , Burkholderia mallei/genética , Burkholderia mallei/fisiología , Burkholderia pseudomallei/genética , Burkholderia pseudomallei/fisiología , Línea Celular , Eliminación de Gen , Immunoblotting , Macrófagos/microbiología , Ratones , Proteínas de Microfilamentos/fisiología , Microscopía Confocal , Datos de Secuencia Molecular , Mutación , Unión Proteica , Homología de Secuencia de AminoácidoRESUMEN
Burkholderia pseudomallei is the causative agent of melioidosis, a serious infectious disease of humans and animals that is endemic in subtropical areas. B. pseudomallei is a facultative intracellular pathogen that may invade and survive within eukaryotic cells for prolonged periods. After internalization, the bacteria escape from endocytic vacuoles into the cytoplasm of infected cells and form membrane protrusions by inducing actin polymerization at one pole. It is believed that survival within phagocytic cells and cell-to-cell spread via actin protrusions is required for full virulence. We have studied the role of a putative type III protein secretion apparatus (Bsa) in the interaction between B. pseudomallei and host cells. The Bsa system is very similar to the Inv/Mxi-Spa type III secretion systems of Salmonella and Shigella. Moreover, B. pseudomallei encodes proteins that are very similar to Salmonella and Shigella Inv/Mxi-Spa secreted proteins required for invasion, escape from endocytic vacuoles, intercellular spread and pathogenesis. Antibodies to putative Bsa-secreted proteins were detected in convalescent serum from a melioidosis patient, suggesting that the system is functionally expressed in vivo. B. pseudomallei mutant strains lacking components of the Bsa secretion and translocation apparatus were constructed. The mutant strains exhibited reduced replication in J774.2 murine macrophage-like cells, an inability to escape from endocytic vacuoles and a complete absence of formation of membrane protrusions and actin tails. These findings indicate that the Bsa type III secretion system plays an essential role in modulating the intracellular behaviour of B. pseudomallei.