A TonB-dependent outer membrane protein as a Bacteroides fragilis fibronectin-binding molecule

• Published in: FEMS immunology and medical microbiology 2009-04, Vol.55 (3), p.388-395
• Main Authors: Pauer, Heidi, Ferreira, Eliane de Oliveira, dos Santos-Filho, Joaquim, Portela, Maristela Barbosa, Zingali, Russolina Benedeta, Soares, Rosangela Maria Araújo, Domingues, Regina Maria Cavalcanti Pilotto
• Format: Article
• Language: English
• Subjects: adherence; Adhesins, Bacterial - genetics; Adhesins, Bacterial - isolation & purification; Adhesins, Bacterial - metabolism; Bacteremia; Bacterial Adhesion; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - isolation & purification; Bacterial Outer Membrane Proteins - metabolism; Bacteroides fragilis; Bacteroides fragilis - chemistry; Bacteroides fragilis - isolation & purification; Bacteroides fragilis - physiology; Chemical treatment; Culture media; DNA, Bacterial - genetics; Electrophoresis; Electrophoresis, Polyacrylamide Gel; Fibronectin; Fibronectin-binding protein; Fibronectins - metabolism; Gel electrophoresis; Humans; Immunoblotting; Membrane proteins; Membranes; Molecular Weight; Organic chemistry; outer membrane protein; Outer membrane proteins; Oxidation; plasmatic fibronectin; Polyacrylamide; Polymerase Chain Reaction - methods; Proteins; Sodium dodecyl sulfate; Sodium lauryl sulfate; Virulence Factors - metabolism
• ISSN: 0928-8244; 1574-695X; 2049-632X
• DOI: 10.1111/j.1574-695X.2009.00532.x

Abstract The binding of Bacteroides fragilis to plasmatic fibronectin was investigated using strains isolated from healthy subjects and from patients with bacteremia. They were cultivated in a synthetic media in which variations in cysteine concentrations determined alterations in the oxidation–reduction potential (Eh). All the strains assayed were capable of adhering to plasmatic fibronectin when cultivated under oxidizing and reducing conditions. Bacteroides fragilis 1405 showed the greatest difference when the results under these conditions were compared and it was selected for further investigations. Chemical treatments suggested the involvement of a protein in the interaction between B. fragilis and plasmatic fibronectin. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of outer membrane proteins (OMPs) revealed differences between the extracts obtained from cultures grown under the two conditions. Protein bands of c. 102, 100, 77, 73, 50 and 40 kDa were more highly expressed under oxidizing than reducing conditions. Dot blot analysis showed a stronger recognition of plasmatic fibronectin by OMPs obtained from cultures grown under higher Eh, and Western blot assays confirmed a band of c. 102 kDa as fibronectin-binding protein. This protein was sequenced and revealed to be a putative TonB-dependent OMPs. PCR analysis confirmed the presence of this gene in all the studied strains.