Crystallization and preliminary X-ray diffraction analysis of lectin-1 from Pseudomonas aeruginosa.

Carbohydrate recognition plays a role in the pathogenesis of Pseudomonas aeruginosa, a common cause of opportunistic infection in humans. Crystals of a carbohydrate-binding protein from P. aeruginosa, lectin PA-1, have now been obtained. The crystals belong to space group I222, with unit-cell parameters a = 40.25, b = 72.30, c = 133.82 A, and diffract to beyond 1.9 A resolution on a rotating-anode X-ray source. Details of crystal-growth conditions, diffraction data collection and processing are reported.

Flow cytometric evaluation of adhesion of Streptococcus pyogenes to epithelial cells.

The precise roles of various surface molecules in the attachment of Streptococcus pyogenes to host epithelia are currently unclear. A flow cytometry assay that facilitates the analysis of the kinetics of S. pyogenes adhesion to epithelial cells was developed. Dose- and time-dependent adhesion isotherms with both buccal epithelial cells (BECs) and Hep-2 cells as substrata were obtained. Although binding equilibrium is reached within 2 h on both cell types, saturation of binding sites on BECs is not achieved within a wide range of experimental conditions. This indicates a high degree of non-specific attachment to that cell type. Since no rinsing step is necessary when using flow cytometry to analyze adhesion, low-affinity associations were observable. This was confirmed by determining bacterial desorption rates early and late in the adsorption process. Binding irregularities were also easily detected since the cytometer records and displays data for up to 10,000 epithelial cells per time point. It is proposed to use this methodology to assign roles to particular surface molecules/characteristics during distinct phases of adhesion.

Hemagglutinin of unusual specificity from Helcococcus kunzii.

Helcococcus kunzii is a gram-positive, catalase-negative opportunist. The organism has been isolated from the lower extremities and breast masses of several patients. A clinical isolate of Helcococcus kunzii was shown to possess a hemagglutinin-lectin with a specificity for N-acetylglucosamine and lactose, two structurally unrelated carbohydrates. The lectin is sensitive to protease, heat and mutanolysin. Electron microscopy failed to reveal fimbriae or fibrillae, suggesting that the lectin is associated with peptidoglycan or the cytoplasmic membrane. It is likely that the lectin is involved in adhesion and colonization of H. kunzii.