A TonB-dependent outer membrane protein as a<i>Bacteroides fragilis</i>fibronectin-binding molecule

Pauer, Heidi; Ferreira, Eliane de Oliveira; Santos-Filho, Joaquim dos; Portela, Maristela Barbosa; Zingali, Russolina B.; Soares, R. Félix; Domingues, Regina Maria Cavalcanti Pilotto

doi:10.1111/j.1574-695x.2009.00532.x

Cited by 17 publications

(20 citation statements)

References 38 publications

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“…This conclusion is in agreement with the observation that fibronectin binds TonBdependent outer membrane receptors present in Bacteroides fragilis, P. multocida, and A. baumannii (39,48,52). However, the molecular factors and processes involved in these interactions are not clear at the moment.…”

Section: Discussionsupporting

confidence: 78%

“…However, the molecular factors and processes involved in these interactions are not clear at the moment. The conclusion that fibronectin binds TonB (39,52) is not in agreement with the known subcellular location and topology of TonB. This is a cytoplasmic membraneanchored protein that spans the periplasmic space, interacts with the N-terminal domain of TonB-dependent outer membrane receptors, and most likely is not exposed to the extracellular environment.…”

Section: Discussionmentioning

confidence: 49%

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Functional Features of TonB Energy Transduction Systems of Acinetobacter baumannii

et al. 2013

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Acinetobacter baumannii is an opportunistic pathogen that causes severe nosocomial infections. Strain ATCC 19606 T utilizes the siderophore acinetobactin to acquire iron under iron-limiting conditions encountered in the host. Accordingly, the genome of this strain has three tonB genes encoding proteins for energy transduction functions needed for the active transport of nutrients, including iron, through the outer membrane. Phylogenetic analysis indicates that these tonB genes, which are present in the genomes of all sequenced A. baumannii strains, were acquired from different sources. Two of these genes occur as components of tonB-exbB-exbD operons and one as a monocistronic copy; all are actively transcribed in ATCC 19606T . The abilities of components of these TonB systems to complement the growth defect of Escherichia coli W3110 mutants KP1344 (tonB) and RA1051 (exbBD) under iron-chelated conditions further support the roles of these TonB systems in iron acquisition. Mutagenesis analysis of ATCC 19606 T tonB 1 (subscripted numbers represent different copies of genes or proteins) and tonB 2 supports this hypothesis: their inactivation results in growth defects in iron-chelated media, without affecting acinetobactin biosynthesis or the production of the acinetobactin outer membrane receptor protein BauA. In vivo assays using Galleria mellonella show that each TonB protein is involved in, but not essential for, bacterial virulence in this infection model. Furthermore, we observed that TonB 2 plays a role in the ability of bacteria to bind to fibronectin and to adhere to A549 cells by uncharacterized mechanisms. Taken together, these results indicate that A. baumannii ATCC 19606 T produces three independent TonB proteins, which appear to provide the energy-transducing functions needed for iron acquisition and cellular processes that play a role in the virulence of this pathogen.

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Section: Discussionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 49%

Functional Features of TonB Energy Transduction Systems of Acinetobacter baumannii

et al. 2013

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“…The function of TonB is apparently to transduce energy to the outer membrane receptors, perhaps by releasing otherwise tightly bound ligands into the periplasmic space [26], [27]. Apart from its capacity to transport molecules, in Pasteurella multocida and Bacteroides fragilis , TonB is able to recognize and bind to fibronectin [22], [28]. It also has been suggested that TonB may allow some species to adhere to and colonize different niches in the host [28].…”

Section: Discussionmentioning

confidence: 99%

Role of Fibronectin in the Adhesion of Acinetobacter baumannii to Host Cells

Smani

McConnell²,

Pachón³

2012

PLoS ONE

117

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Adhesion to host cells is an initial and important step in Acinetobacter baumannii pathogenesis. However, there is relatively little information on the mechanisms by which A. baumannii binds to and interacts with host cells. Adherence to extracellular matrix proteins, such as fibronectin, affords pathogens with a mechanism to invade epithelial cells. Here, we found that A. baumannii adheres more avidly to immobilized fibronectin than to control protein. Free fibronectin used as a competitor resulted in dose-dependent decreased binding of A. baumannii to fibronectin. Three outer membrane preparations (OMPs) were identified as fibronectin binding proteins (FBPs): OMPA, TonB-dependent copper receptor, and 34 kDa OMP. Moreover, we demonstrated that fibronectin inhibition and neutralization by specific antibody prevented significantly the adhesion of A. baumannii to human lung epithelial cells (A549 cells). Similarly, A. baumannii OMPA neutralization by specific antibody decreased significantly the adhesion of A. baumannii to A549 cells. These data indicate that FBPs are key adhesins that mediate binding of A. baumannii to human lung epithelial cells through interaction with fibronectin on the surface of these host cells.

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“…Particle agglutination assay. Latex particles (0.83 mm diameter; Sigma) coated with plasma fibronectin (Sigma) were prepared according to Pauer et al (2009). All the B. fragilis strains were grown for 18 h at 37 uC in BHI broth, centrifuged (3000 g for 10 min) and washed once in 0.1 M PBS (pH 7.2).…”

Section: Methodsmentioning

confidence: 99%

Inactivation of a fibronectin-binding TonB-dependent protein increases adhesion properties of Bacteroides fragilis

Pauer

Cavalcanti

Teixeira

et al. 2013

Journal of Medical Microbiology

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Bacteroides fragilis is the Gram-negative strictly anaerobic bacterium most frequently isolated from clinical infections, including intra-abdominal abscess and bacteraemia. A number of factors can contribute to its virulence, including the expression of adhesins. Some of them are already characterized and can recognize and bind to extracellular matrix components, such as fibronectin. One of the molecules responsible for fibronectin-binding is an outer-membrane protein previously described by our group, which belongs to the TonB-dependent family. The aim of the present work was to characterize this protein. Initially, it was confirmed by fluorescence and electron microscopy that the fibronectin-binding molecules were located in the bacterial surface, but the distribution of these molecules on the surface was not uniform. To further evaluate the role of this protein, the gene bf1991, responsible for encoding this protein, was inactivated by a suicide vector and the mutant strains generated were used in several experiments to verify possible phenotypical alterations. In adherence assays with fibronectin immobilized on latex beads an increased adhesion was observed with the mutant strains compared with the wild-type strain. Western blot analysis in the mutant strain revealed the absence of the 120 kDa TonB-dependent outer-membrane protein and an alteration in the expression of an unknown 30 kDa protein. Killing assays using peritoneal macrophages were performed to evaluate the role of this protein as a virulence attribute and it was observed that the mutant strains were more efficiently internalized than the wild-type strains, with more internalization in the samples covered with fibronectin than in the samples not covered with it.

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A TonB-dependent outer membrane protein as aBacteroides fragilisfibronectin-binding molecule

Cited by 17 publications

References 38 publications

Functional Features of TonB Energy Transduction Systems of Acinetobacter baumannii

Functional Features of TonB Energy Transduction Systems of Acinetobacter baumannii

Role of Fibronectin in the Adhesion of Acinetobacter baumannii to Host Cells

Inactivation of a fibronectin-binding TonB-dependent protein increases adhesion properties of Bacteroides fragilis

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