The populations studied here may represent separate geographical ecotypes, where metabolic control and protein synthesis/folding mechanisms has been finely tuned to confer fitness to local environmental pressures such as climate

antibodies. Consistent with earlier work in S. cerevisiae the initial distribution of Als5pWT was random. Pulling on single adhesins with the AFM tip induced the formation of 955365-80-7 adhesion domains of 100-500 nm size. In addition, the forceinduced nanodomains propagated over the entire cell surface, since remote areas showed similar nanodomains. Als5pWT remodelling was independent of cellular metabolic activity since heat-killed cells show the same behavior as live cells. Remarkably, Als5p clustering properties were almost completely abolished in the V326N mutant, indicating that amyloid interactions play a key role in clustering. Because amyloid regions also appear in C. albicans and are accompanied by development of strong adhesion and surface birefringence, we tested to see if there was similar force-induced formation of adhesin nanodomains in C. albicans. In this case, living C. albicans yeast cells were probed with AFM tips bearing Als5p1-433 fragments since these bind to all Als adhesins. As expected, the initial force mapping showed a random pattern of Als proteins, with a surface density being greater than in the S. cerevisiae surface display model. The adhesive forces were typical for Als-Als interactions. Force-extension curves showed patterns similar to those reported earlier for Als5p-Als5p interactions, except that the number of unfolding Tandem Repeat domains varied from 33, the range known for Als alleles. Upon remapping of the same region or a remote region on the same cell, the adhesin molecules were clustered, as in the S. cerevisiae model. These observations lead us to conclude that nanodomains form and propagate in response to force in C. albicans, just as they do in Als5pWT-expressing S. cerevisiae. Adhesion nanodomains are also visualized by confocal microscopy of thioflavin T-stained cells. Therefore we tested the effects of the peptides on nanodomain formation in C. albicans. As in the Als5p S. cerevisiae surface display cells, the native sequence peptide potentiated nanodomain formation and the V326N substitution peptide inhibited nanodomains. The sequence specificity of nanodomain potentiation and inhibition implies that Als proteins are major components of surface amyloids in C. albicans. The amyloid sequence of Als5p is critical for cell-cell association and cellubstrate adhesion to polystyrene We also tested to determine whether amyloid formation was important for a model biofilm. S. cerevisiae expressing Als5pWT or C. albicans adhered to the polystyrene surface of a 96-well plate in Tris-EDTA buffer. The non-adherent cells and buffer were removed, and the adhering cells incubated in medium overnight. Microscopy and quantitative crystal violet staining of the wells revealed 21609844 that Als5pWT-expressing S. cerevisiae and C. albicans strains bound to the surface in aggregates. Thioflavin T partially dispersed the C. albicans aggregates and fully dispersed the Als5pWT-mediated aggregates of S. cerevisiae. This thioflavin T treatment reduced adherence of Als5p-expressing S. cerevisiae by about 16%, and C. albicans adherence by 45%. A 90-fold higher concentration of dye reduced adherence to the plastic by 79% and 90% respectively. Congo red had similar effects: 100 nM disrupted aggregates and partially inhibited adherence; 300 mM blocked almost all adhesion. In contrast to cells expressing Als5pWT, Als5pV326N cells bound to the surface as dispersed cells, rather than as aggregates. The lower concentrations of the dyes did n

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