Characterisation of potential adhesins of the bacterium Pasteuria penetrans, and of putative receptors on the cuticle of Meloidogyne incognita, a nematode host.

Pasteuria penetrans spores were fragmented by glass bead vortexing, producing exosporial membranes and spore fragments, which consisted of fibre bundles. Both exosporia and spore fragments are capable of host-specific attachment to the cuticle of Meloidogyne incognita, a root-knot nematode host. Putative M. incognita receptors appear to be soluble in beta-mercaptoethanol (BME) but not SDS, and are also sensitive to tryptic digestion and deglycosylation by endoglycosidase F. Polyclonal antibodies against intact spores and spore fragments of antispore antibodies produced 100% inhibition. The antibodies, however, did not show preferential staining of particular spore structures in thin section immunolabelling studies. Exposure of Pasteuria penetrans spores to HCl or urea-SDS-dithiothreitol renders them incapable of attachment to their host juveniles and extensively disrupts fibres that surround the spore core. Protein extracts from spore fragments or from exosporial membranes are identical, and urea-BME extracts from either structure, but not SDS extracts, can inhibit the attachment of spores to juveniles by 60-80%. An inhibitory BME extract from spore fragments was analysed by anion-exchange chromatography and adsorption onto host cuticle followed by immunoblotting. It appeared to contain six potential spore adhesins of approximate Mr 24-29, 38-47, 59, 89, 126, and 190 (x10(3)). Lectin affinity blotting with wheat germ agglutinin and concanavalin A showed that all of these proteins bear terminal N-acetylglucosamine residues and the 38-47 kDa band also bears terminal Glc/Man residues.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial biochemical characterization of cell surface hydrophobicity and hydrophilicity of Candida albicans.

Hydrophobic yeast cells of Candida albicans are more virulent than hydrophilic yeast cells in mice. Results of experiments performed in vitro suggest that surface hydrophobicity contributes to virulence in multiple ways. Before definitive studies in vivo concerning the contribution of fungal surface hydrophobicity to pathogenesis can be performed, biochemical, physiological, and immunochemical characterization of the macromolecules responsible for surface hydrophobicity must be accomplished. This report describes our initial progress toward this goal. When hydrophobic and hydrophilic yeast cells of C. albicans were exposed to various enzymes, only proteases caused any change in surface hydrophobicity. Hydrophobic cell surfaces were sensitive to trypsin, chymotrypsin, pronase E, and pepsin. This indicates that surface hydrophobicity is due to protein. Papain, however, had no significant effect. The hydrophobicity of hydrophilic cells was altered only by papain. The proteins responsible for surface hydrophobicity could be removed by exposure to lyticase, a beta 1-3 glucanase, for 30 to 60 min. When 60-min lyticase digests of hydrophobic and hydrophilic cell walls were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with a 12.5% resolving gel, each protein population contained a single unique protein that was not evident in the other protein population. However, when the cell wall surface proteins of hydrophobic and hydrophilic cells were first labeled with 125I and then removed by lyticase and analyzed by SDS-PAGE, at least four low-molecular-mass (less than 65 kilodaltons) proteins associated with hydrophobic cells were either absent or much less abundant in the hydrophilic cell digests. This result was seen for both C. albicans strains that we tested. When late-exponential-phase hydrophilic cells were treated with tunicamycin, high levels of surface hydrophobicity were obtained by stationary phase. These results indicate that the surface hydrophobicity of C. albicans reflects changes in external surface protein exposure and that protein mannosylation may influence exposure of hydrophobic surface proteins.