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Identification of a 349-Kilodalton Protein (Gli349) Responsible for Cytadherence and Glass Binding during Gliding of Mycoplasma mobile. Atsuko Uenoyama, 2004.Several mycoplasma species are known to glide in the directionof the membrane protrusion [head-like structure], but the mechanism underlying this movement is entirely unknown . To identify proteins involved in the gliding mechanism, protein fractions of Mycoplasma mobile were analyzed for 10 gliding mutants isolated previously. One large protein [Gli349] was observed to be missing in a mutantm13 deficient in hemadsorption and glass binding . The predictedamino acid sequence indicated a 348,758-Da protein that wastruncated at amino acid residue 1257 in the mutant . Immunofluorescencemicroscopy with a monoclonal antibody showed that Gli349 islocalized at the head-like protrusion's base, which we designatedthe cell neck, and immunoelectron microscopy established thatthe Gli349 molecules are distributed all around this neck . Thenumber of Gli349 molecules on a cell was estimated by immunoblotanalysis to be 450 ± 200 . The antibody inhibited boththe hemadsorption and glass binding of M . mobile . When the antibodywas used to treat gliding mycoplasmas, the gliding speed andthe extent of glass binding were inhibited to similar extentsdepending on the concentration of the antibody . This suggestedthat the Gli349 molecule is involved not only in glass bindingfor gliding but also in movement . To explain the present results,a model for the mechanical cycle of gliding is discussed. Characterization of NopP, a Type III Secreted Effector of Rhizobium sp . Strain NGR234. Nora Ausmees, 2004.The type three secretion system (TTSS) encoded by pNGR234a, the symbiotic plasmid of Rhizobium sp . strain NGR234, is responsible for the flavonoid- and NodD1-dependent secretion of nodulation outer proteins (Nops) . Abolition of secretion of all or specific Nops significantly alters the nodulation ability of NGR234 on many of its hosts . In the closely related strain Rhizobium fredii USDA257, inactivation of the TTSS modifies the host range of the mutant so that it includes the improved Glycine max variety McCall . To assess the impact of individual TTSS-secreted proteins on symbioses with legumes, various attempts were made to identify nop genes . Amino-terminal sequencing of peptides purified from gels was used to characterize NopA, NopL, and NopX, but it failed to identify SR3, a TTSS-dependent product of USDA257 . By using phage display and antibodies that recognize SR3, the corresponding protein of NGR234 was identified as NopP . NopP, like NopL, is an effector secreted by the TTSS of NGR234, and depending on the legume host, it may have a deleterious or beneficial effect on nodulation or it may have little effect . Bacterial Strains Isolated from Different Niches Can Exhibit Different Patterns of Adhesion to Substrata. Dewi P. Bakker, 2004.Various mechanisms have been demonstrated to be operative in bacterial adhesion to surfaces, but whether bacterial adhesion to surfaces can ever be captured in one generally valid mechanism is open to question . Although many papers in the literature make an attempt to generalize their conclusions, the majority of studies of bacterial adhesion comprise only two or fewer strains . Here we demonstrate that three strains isolated from a medical environment have a decreasing affinity for substrata with increasing surface free energy, whereas three strains from a marine environment have an increasing affinity for substrata with increasing surface free energy . Furthermore, adhesion of the marine strains related positively with substratum elasticity, but such a relation was absent in the strains from the medical environment . This study makes it clear that strains isolated from a given niche, whether medical or marine, utilize different mechanisms in adherence, which hampers the development of a generalized theory for bacterial adhesion to surfaces . Involvement of a Sialic Acid-Binding Lectin with Hemagglutination and Hydrophobicity of Flavobacterium psychrophilum. Jeannette Dan Møller, 2003.Strains of Flavobacterium psychrophilum were studied for their ability to adhere and cause agglutination of erythrocytes and yeast cells . Strains of the serotype Th showed low or no hemagglutinating (HA) properties toward human, avian, bovine, and rainbow trout erythrocytes, whereas strains of serotype Fd and FpT exhibited distinct HA properties . None of the strains was able to cause agglutination of yeast cells . Greater adherence specificity toward rainbow trout blood cells was seen for the HA-positive strains . Growth at 5°C, compared to that at 15°C, induced an increase in the hemagglutination of some strains . HA activities of F . psychrophilum were inhibited only by sialic acid (N-acetyl-neuraminic acid), heat treatment at 65°C, and proteinase K treatment and not by any of seven other carbohydrates, periodate oxidation, or treatment with trypsin . The supernatant from washed bacterial cells also showed some HA properties . All strains were shown to be highly hydrophobic by the hydrophobic interaction chromatography test, although some contradictions to the results of the salt aggregation test (showing some strains as less hydrophobic) were seen . These results indicate that the aggregation of F . psychrophilum and erythrocytes depend on a lectin present on the surface of HA-positive F . psychrophilum strains and absent on HA-negative strains . This lectin reacts specifically with sialic acid . The adhesion differences observed for F . psychrophilum strains do not appear to correlate with the virulence but still provide insights into the interaction of F . psychrophilum and rainbow trout .
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