A Bacteroides fragilis surface glycoprotein mediates the interaction between the bacterium and the extracellular matrix component laminin-1.

The adherence of Bacteroides fragilis strains to immobilized laminin-1 (LMN-1) was investigated using this protein adsorbed onto glass. Among the 27 strains isolated from infectious processes and assayed, 13 presented strong adherence to LMN-1. Among them, two strains, MC2 and 1081, showed the strongest association, and for that reason they were selected for further studies in which adherence to this protein was confronted with both physical-chemical and enzymatic treatments, along with concurrence assays with the LMN-1 molecule itself and the LMN-1-residing amino acid sequences (RGD, IKVAV, YIGSR, AG73, A13 and C16). The chemical and enzymatic treatments resulted in sharp decreases in binding rates of those strains, and competition experiments with LMN-1- residing amino acids revealed that, except for RGD and A13, all the others were effective at reducing bacterial binding of the bacteria. The outer membrane proteins (OMPs) of B. fragilis were extracted and assayed onto dot-blotted LMN-1, and when the extracts were chemically treated, especially with metasodium periodate, a drastic reduction in bacterial binding occurred. Results of the latter assays clearly indicate that bacterial molecules involved in both recognition and binding of B. fragilis to LMN-1 are present in OMP extracts. Taken together, our results strongly indicate that a B. fragilis surface glycoprotein may play a key role in bacterial association with LMN-1.

Iron modulates ecto-phosphohydrolase activities in pathogenic trichomonads.

The presence of iron in the extracellular medium is essential for both in vivo and in vitro survival of pathogenic microorganisms, including Trichomonas vaginalis and Tritrichomonas foetus. In these parasites, iron is directly involved in the proliferation, protein expression and activation of critical enzymes. The purpose of this study was to investigate the role of iron in ecto-ATPase, ecto-phophatase and secreted phosphatase activities of these trichomonads. We observed that trichomonads grown in iron-depleted medium exhibited a remarkable decrease in both ecto-ATPase and ecto-phosphatase activities, when compared to those cultivated under control conditions (iron-rich medium). Furthermore, parasites grown in iron-depleted medium restored their enzyme activities when they were re-inoculated into fresh iron-rich medium. We demonstrated that modulation of ecto-phosphohydrolase activities is due neither to enzyme-iron nor to substrate-iron complex formation, since iron addition directly to the medium where the enzymatic reactions occurred did not alter their activities. Previously, we had reported that a fresh clinical isolate of T. vaginalis was much more cytotoxic to epithelial cell monolayers than a long-term cultured one. In this study we witnessed that the fresh isolate of T. vaginalis presented higher activities to all herein investigated enzymes than the long-term cultured one. Altogether, our data clearly point out that iron has a pivotal role in the expression of phosphohydrolases in both trichomonads.

Differential soluble protein expression between Trichomonas vaginalis isolates exhibiting low and high virulence phenotypes.

A comparative analysis of proteomic maps of long-term grown and fresh clinical Trichomonas vaginalis isolates exhibiting low and high virulence phenotypes, respectively, was performed using two-dimensional gel electrophoresis and mass spectrometry. Of 29 protein spots differentially expressed between the isolates, 19 were over-expressed in the isolate exhibiting high virulence phenotype: proteins associated with cytoskeletal dynamics, such as coronin and several isoforms of actin, as well as proteins involved in signal transduction, protein turnover, proteolysis, and energetic and polyamine metabolisms were identified. Some malate dehydrogenase, fructose-1,6-bisphosphate aldolase and ornithine cyclodeamidase isoforms were exclusively expressed by the highly virulent isolate. During interaction assays with VEC, parasites exhibiting high virulence phenotype rapidly adhered and switched to amoeboid forms. In contrast, low adhesion and no morphological transformation were observed in parasites displaying low virulence phenotype. Our findings demonstrate that expression of specific proteins by high and low virulence parasites could be associated with the ability of each isolate to undergo morphological transformation and interact with host cells. Such data represent an important step towards understanding of the complex interaction network of proteins that participate in the mechanism of pathogenesis of this protozoan.