Adherence Of Yeast Cells Research Articles

Affinity Adhesion of Carbohydrate Particles and Yeast Cells to Boronate‐Containing Polymer Brushes Grafted onto Siliceous Supports

Cross-linked agarose particles (Sepharose CL-6B) and baker's yeast cells were found to adhere to siliceous supports end-grafted with boronate-containing copolymers (BCCs) of N,N-dimethylacrylamide at pH> or =7.5, due to boronate interactions with surface carbohydrates of the particles and the cells. These interactions were registered both on macroscopic and on molecular levels: the BCCs spontaneously adsorbed on the agarose gel at pH> or =7.5, with adsorption increasing with pH. Agarose particles and yeast cells stained with Procion Red HE-3B formed stable, monolayer-like structures at pH 8.0, whereas at pH 7.0-7.8 the structures on the copolymer-grafted supports were less stable and more random. At pH 9.0, 50 % saturation of the surface with adhering cells was attained in 2 min. Stained cells formed denser and more stable layers on the copolymer-grafted supports than they did on supports modified with self-assembled organosilane layers derivatized with low-molecular-weight boronate, presumably due to a higher reactivity of the grafted BCCs. Quantitative detachment of adhered particles and cells could be achieved by addition of 20 mM fructose--a strong competitor for binding to boronates--at pH 7.0-9.0. Regeneration of the grafted supports allowed several sequential adhesion and detachment cycles with stained yeast cells. Affinity adhesion of micron-sized carbohydrate particles to boronate-containing polymer brushes fixed on solid supports is discussed as a possible model system suggesting a new approach to isolation and separation of living cells.

Kinetics of yeast detachment from controlled stainless steel surfaces

Using a radial flow chamber, we study Saccharomyces cerevisiae kinetics of detachment from stainless steel substrates. Samples of similar surface chemistry, but with different surface topologies are compared: mirror polished and electro-chemically etched. Different grain sizes (20, 40 and 100 μm) and different etching depths (100–650 nm) are tested. Cells are removed from the substrate according to a first-order kinetics defining two macroscopic parameters that depend on the applied stress: the detachment efficiency and the detachment rate constant. Whatever the surface topology, detachment occurs above a threshold and its rate is strongly stimulated by the applied stress. The detachment efficiency is characterized by the shear stress at which half of the cells detach and is independent of surface topology. In contrast, detachment is faster from etched than mirror polished surfaces. Finally, we also show the preferential adhesion of yeast cells to grains of <0 0 1> crystallographic orientation with respect to the surface.

Effect of surface hydrophobicity on the adhesion of S. cerevisiae onto modified surfaces by poly(styrene-ran-sulfonic acid) random copolymers

The hydrophobicity of solid surfaces has been regarded as a controlling factor in microbial adhesion phenomena. In this study, the surface hydrophobicity was modified by coating with a poly(styrene-ran-sulfonic acid) random copolymer (PS- x-SA, charge density ( x): 0–15.3%), and the adhesion rate, J 0, of S. cerevisiae performed with a direct observation technique. The results indicated that the degree of sulfonation of PS- x-SA greatly influenced the hydrophobicity of substrates and the adhesion of yeast cells. The J 0 of PS- x-SA substrates were gradually decreased as increasing charge density. The interactions between cells and substrates explained by the XDLVO theory, predicted that the decrease of J 0 as increasing charge density was not due to the increase of electric double layer repulsion, but mainly due to the hydrophobic acid–base interactions. Also, it predicted that microbial adhesions of PS- x-SA were mostly reversible, while some of PS and PS-5.1-SA adhered cells were hardly removed. Based on these results, XDLVO theory was effective for predicting adhesion phenomena of S. cerevisiae onto the PS- x-SA-coated substrates.

Transcriptional profiling of Saccharomyces cerevisiae cells under adhesion-inducing conditions

The ability to adhere to other cells is one of the most prominent determinants of fungal pathogenicity. Thus, adherence of fungi to human tissues or plastics triggers hospital-acquired fungal infections, which are an increasing clinical problem, especially in immunocompromised persons. In the model fungus Saccharomyces cerevisiae adhesion can be induced by starvation for amino acids, and depends on the transcriptional activator of the general amino acid control system, Gcn4p. However, not much is known about the transcriptional program that mediates adhesive growth under such conditions. In this study, we present a genome-wide transcriptional analysis of Sigma1278b yeast cells that were subjected to adhesion-inducing conditions imposed by amino acid starvation. Twenty-two novel genes were identified as inducible by amino acid starvation; 72 genes belonging to different functional groups, which were not previously known to be regulated by Gcn4p, require Gcn4p for full transcriptional induction under adhesion-inducing conditions. In addition, several genes were identified in Sigma1278b cells that were inducible by amino acid starvation in a Gcn4p-independent manner. Our data suggest that adhesion of yeast cells induced by amino acid starvation is regulated by a complex, Sigma1278b-specific transcriptional response.

Modifying stainless steel surfaces with responsive polymers: effect of PS-PAA and PNIPAAM on cell adhesion and oil removal

The treatment of stainless steel surfaces with responsive polymers was investigated using X-ray photoelectron spectroscopy and scanning electron microscopy. Poly(N-isopropylacrylamide) (PNIPAAM) is a temperature-sensitive polymer which is soluble in water below 32°C (Lower Critical Solubility Temperature (LCST)) but collapses and aggregates above 32°C. This polymer was adsorbed at 50°C from solutions at different concentrations, followed by rinsing and different drying procedures. Thereby, a large variety of surface structures could be obtained, from smooth films to surfaces showing marked relief features due to residues of PNIPAAM aggregates. Two poly(styrene)-b-poly(acrylic acid), PS-PAA, with different block lengths, were spin-coated on stainless steel and showed preferential exposure of PS blocks at the outermost surface. PNIPAAM-conditioning was shown to strongly reduce yeast cell adhesion and to facilitate the removal of oil soil due to its high water affinity and chain mobility below the LCST. PS-PAA coatings also reduced yeast cell adhesion; this may partly be due to a reorganization of the surface, leading to exposure of PAA chains in contact with water and thus to electrostatic repulsion of the yeast cells.

Fungal infection in the very low birthweight infant.

Fungal infections are prevalent in very low birthweight (<1500 g) infants and are associated with significant morbidity and mortality. A better understanding of the adherence factors, molecular diagnostics and risk factors for invasive fungal infection are important in treatment and prevention. Animal studies have demonstrated that Candida readily adheres to apical microvilli and the junctions between enterocytes. Although antibiotics facilitate colonization, dissemination occurs with immunosuppression. The INT1 gene is associated with enhanced colonization and dissemination in these animal models. Dissemination is probably caused by yeast cell adherence and invasion, whereas tissue injury may be related to filamentous formation. Polymerase chain reaction techniques have demonstrated promise in neonatal patients and may not only detect bloodstream infection, but fungal infection at other sites. At the time of fungal sepsis, less than 28 weeks' gestation, thrombocytopenia, and previous exposure to broad-spectrum antibiotics continue to be risk factors for infection. Empiric therapy is still being defined and investigated. Fluconazole prophylaxis should be strongly considered in the most immature infants. Preventative strategies against fungal colonization and infection are critical in high-risk very low birthweight infants. Also promising is the ability of molecular diagnostics to detect infection earlier, allowing for prompt treatment, including central venous catheter removal. Identifying the highest risk very low birthweight infants for prophylaxis and empiric therapy may lead to better outcomes. Multicenter clinical trials of fluconazole prophylaxis to confirm its safety and efficacy, and of empiric treatment to test safety and outcomes are urgently needed.

Yeast cell adhesion on oligopeptide modified surfaces

Self-assembling oligopeptides are novel materials with potential bioengineering applications; this paper explores the use of one of these oligopeptides, EAK 16 II, for modifying the surface properties of cell-supporting substrates. To characterize the surface properties, thermodynamic measurements of liquid contact angle and surface free energy were correlated to atomic force microscopy (AFM) observations. A critical concentration of 0.1 mg/ml was found necessary to completely modify the surface properties of the substrate with EAK 16 II. Adhesion of a yeast cell, Candida utilis, was modified by the coating of EAK 16 II on both hydrophobic (plastic) and hydrophilic (glass) surfaces: Cell coverage was slightly enhanced on the glass substrate, but decreased significantly on the plastic substrate. This indicates that the yeast cell adhesion was mainly determined via hydrophobic interactions between the substrate and the cell wall. However, on the EAK 16 II modified glass substrate, surface roughness might be a factor in causing a slightly larger cell adhesion than that on bare glass. The morphology of adhered cells was also obtained with AFM imaging, showing a depression at the center of the cell on all substrates. Small depressions on the oligopeptide-coated surfaces and plastic substrate may indicate good water-retaining ability by the cell. There was no apparent difference in cell adhesion and morphology among cells obtained from lag, exponential and stationary growth phases.

Candida albicans expresses a focal adhesion kinase-like protein that undergoes increased tyrosine phosphorylation upon yeast cell adhesion to vitronectin and the EA.hy 926 human endothelial cell line.

The signaling pathways triggered by adherence of Candida albicans to the host cells or extracellular matrix are poorly understood. We provide here evidence in C. albicans yeasts of a p105 focal adhesion kinase (Fak)-like protein (that we termed CaFak), antigenically related to the vertebrate p125Fak, and its involvement in integrin-like-mediated fungus adhesion to vitronectin (VN) and EA.hy 926 human endothelial cell line. Biochemical analysis with different anti-chicken Fak antibodies identified CaFak as a 105-kDa protein and immunofluorescence and cytofluorimetric analysis on permeabilized cells specifically stain C. albicans yeasts; moreover, confocal microscopy evidences CaFak as a cytosolic protein that colocalizes on the membrane with the integrin-like VN receptors upon yeast adhesion to VN. The protein tyrosine kinase (PTK) inhibitors genistein and herbimycin A strongly inhibited C. albicans yeast adhesion to VN and EA.hy 926 endothelial cells. Moreover, engagement of alpha v beta 3 and alpha v beta 5 integrin-like on C. albicans either by specific monoclonal antibodies or upon adhesion to VN or EA.hy 926 endothelial cells stimulates CaFak tyrosine phosphorylation that is blocked by PTK inhibitor. A role for CaFak in C. albicans yeast adhesion was also supported by the failure of VN to stimulate its tyrosine phosphorylation in a C. albicans mutant showing normal levels of CaFak and VNR-like integrins but displaying reduced adhesiveness to VN and EA.hy 926 endothelial cells. Our results suggest that C. albicans Fak-like protein is involved in the control of yeast cell adhesion to VN and endothelial cells.

Involvement of fungal cell wall components in adhesion of Sporothrix schenckii to human fibronectin.

Systemic sporotrichosis is an emerging infection potentially fatal for immunocompromised patients. Adhesion to extracellular matrix proteins is thought to play a crucial role in invasive fungal diseases. Here we report studies of the adhesion of Sporothrix schenckii to the extracellular protein fibronectin (Fn). Both yeast cells and conidia of S. schenckii were able to adhere to Fn as detected by enzyme-linked immunosorbent binding assays. Adhesion of yeast cells to Fn is dose dependent and saturable. S. schenckii adheres equally well to 40-kDa and 120-kDa Fn proteolytic fragments. While adhesion to Fn was increased by Ca(2+), inhibition assays demonstrated that it was not RGD dependent. A carbohydrate-containing cell wall neutral fraction blocked up to 30% of the observed adherence for the yeast cells. The biochemical nature of this fraction suggests the participation of cell surface glycoconjugates in binding by their carbohydrate or peptide moieties. These results provide new data concerning S. schenckii adhesion mechanisms, which could be important in host-fungus interactions and the establishment of sporotrichosis.

Adherence and invasion studies of Candida albicans strains, using in vitro models of esophageal candidiasis.

The adherence of clinical and commensal isolates and reference collection strains of Candida albicans to a human esophageal cell monolayer (HET1-A) and reconstituted human esophageal tissue was compared. Isolates from patients with a severe form of esophageal candidiasis or candidemia adhered to HET1-A cells to a significantly greater extent than did isolates from patients with mild esophageal candidiasis or commensal and reference collection strains. In addition, C. albicans strain SSK21, which lacks the ssk1 response regulator gene of a 2-component signal transduction pathway, adhered less readily to the HET1-A cells than did parental cells or a gene-reconstituted strain. In a reconstituted esophageal tissue model, all clinical strains but not commensal or reference collection strains penetrated the epithelium, albeit at different rates. Hyphal formation following yeast cell adherence to the esophageal tissue was a requirement for invasion. Scanning electron microscopy was also used to confirm the colonization of the esophageal tissues by various strains. These studies indicate that both the HET1-A and the reconstituted esophageal tissue models can be used as in vitro targets to evaluate the adherence phenotype and invasiveness of C. albicans strains.

Environmentally induced reversible conformational switching in the yeast cell adhesion protein alpha-agglutinin.

The yeast cell adhesion protein alpha-agglutinin is expressed on the surface of a free-living organism and is subjected to a variety of environmental conditions. Circular dichroism (CD) spectroscopy shows that the binding region of alpha-agglutinin has a beta-sheet-rich structure, with only approximately 2% alpha-helix under native conditions (15-40 degrees C at pH 5.5). This region is predicted to fold into three immunoglobulin-like domains, and models are consistent with the CD spectra as well as with peptide mapping and site-specific mutagenesis. However, secondary structure prediction algorithms show that segments comprising approximately 17% of the residues have high alpha-helical and low beta-sheet potential. Two model peptides of such segments had helical tendencies, and one of these peptides showed pH-dependent conformational switching. Similarly, CD spectroscopy of the binding region of alpha-agglutinin showed reversible conversion from beta-rich to mixed alpha/beta structure at elevated temperatures or when the pH was changed. The reversibility of these changes implied that there is a small energy difference between the all-beta and the alpha/beta states. Similar changes followed cleavage of peptide or disulfide bonds. Together, these observations imply that short sequences of high helical propensity are constrained to a beta-rich state by covalent and local charge interactions under native conditions, but form helices under non-native conditions.

Conditioning film and environmental effects on the adherence of Candida spp. to silicone and poly(vinylchloride) biomaterials.

The reported incidence of colonization of oropharyngeal medical devices with Candida spp. has increased in recent years, although few studies that have systematically examined the adherence of yeast cells to such biomaterials, the primary step in the process of colonization. This study, therefore, examined the effects of oropharyngeal atmospheric conditions (5% v/v carbon dioxide) and the presence of a salivary conditioning film on both the surface properties and adherence of Candida albicans, Candida krusei and Candida tropicalis to PVC and silicone. Furthermore, the effects of the salivary conditioning film on the surface properties of these biomaterials are reported. Growth of the three Candida spp. in an atmosphere containing 5% v/v CO2 significantly increased their cell surface hydrophobicity and reduced the zeta potential of C. albicans and C. krusei yet increased the zeta potential of C. tropicalis (p<0.05). Furthermore, growth in 5% v/v CO2 decreased the adherence of C. tropicalis and C. albicans to both PVC and silicone, however, increased adherence of C. krusei (p<0.05). Pre-treatment of the microorganisms with pooled human saliva significantly decreased their cell surface hydrophobicity and increased their adherence to either biomaterial in comparison to yeast cells that had been pre-treated with PBS (p<0.05). Saliva treatment of the microorganisms had no consistent effect on microbial zeta potential. Interestingly, adherence of the three, saliva-treated Candida spp. to saliva-treated silicone and PVC was significantly lower than whenever the microorganisms and biomaterials had been treated with PBS (p<0.05). Treatment of silicone and PVC with saliva significantly altered the surface properties, notably reducing both the advancing and receding contact angles and, additionally, the microrugosity. These effects may contribute to the decreased adherence of saliva-treated microorganisms to these biomaterials. In conclusion, this study has demonstrated the effects of physiological conditions within the oral cavity on the adherence of selected Candida spp. to biomaterials employed as oropharyngeal medical devices. In particular, this study has ominously shown that these materials act as substrates for yeast colonization, highlighting the need for advancements in biomaterial design. Furthermore, it is important that physiological conditions should be employed whenever biocompatibility of oropharyngeal biomaterials is under investigation.

Effect of salivary secretory IgA on the adhesion of Candida albicans to polystyrene.

Attachment of Candida albicans to plastic materials of dental prostheses or to salivary macromolecules adsorbed on their surface is believed to be a critical event in the development of denture stomatitis. In an earlier study, it was shown that adhesion of C. albicans to polystyrene, a model system to study the adhesion of C. albicans to plastic materials, can be partially inhibited with an mAb directed against cell wall polysaccharides of C. albicans. In the present study, the role of whole saliva in the adhesion of C. albicans to polystyrene has been investigated, and three mAbs directed against epitopes of cell wall mannoproteins have been used to mimic the inhibitory effect observed with salivary secretory IgA (sIgA) on the adhesion of C. albicans to polystyrene. In the absence of whole saliva, adherence of C. albicans 3153 increased with germination. However, the presence of whole saliva enhanced the adhesion to polystyrene of C. albicans 3153 yeast cells but decreased the adhesion of germinated cells. The enhancement of adhesion of yeast cells to polystyrene mediated by saliva was confirmed with an agerminative mutant of C. albicans 3153. The inhibition of the adhesion of C. albicans 3153 germ tubes to polystyrene was due to the salivary sIgA since sIgA-depleted saliva enhanced the adhesion of C. albicans 3153 to polystyrene. The inhibitory effect mediated by sIgA was not related to the inhibition of germination but to the blockage of adhesins expressed on the cell wall surface of the germ tubes. The three mAbs studied reduced the adhesion of C. albicans 3153 to polystyrene at levels equivalent to those for purified sIgA. The highest reduction in the adhesion was obtained with the IgA mAb N3B. The best results were obtained when the three mAbs were combined. The results suggest that whole saliva plays a different role in the adhesion of C. albicans to polystyrene depending on the morphological phase of C. albicans. These results may give new insights into the conflicting role of saliva in the adhesion of C. albicans to plastic materials of dental prostheses.

Adherence in tissues of immunocompromised mice of a non-mycelium producing strain of Candida albicans.

A non-mycelial strain of wild-type Candida albicans strain 3153 A was produced by repeated subculturing on Sabouraud glucose agar, and maintained on yeast extract-peptone-glucose medium resulting in hydrophobic cells at 26 degrees C and hydrophilic cells at 37 degrees C. The behaviour of cells of this strain was studied in male BALB/c mice, immunocompromised by treatment with cyclophosphamide and cortisone acetate. An ex-vivo assay of cell adherence to tissue sections of liver, spleen, kidney and lymph-nodes was used. The adherence of yeast cells at 26 and 37 degrees C was predominantly produced by hydrophobic cells and was significantly greater in spleen and liver of immunosuppressed mice compared with the organs of control animals. Adhesion was observed in the white and red pulp as well as in the marginal zone of the spleen.

Identification of sialic acids on the cell surface of Candida albicans

The cell-surface expression of sialic acids in two isolates of Candida albicans was analyzed by thin-layer and gas chromatography, binding of lectins, colorimetry, sialidase treatment and flow cytofluorimetry with fluorescein-labeled lectins. N-acetylneuraminic acid (NANA) was the only derivative found in both strains of C. albicans grown in a chemically defined medium. Its identification was confirmed by mass spectrometry in comparison with an authentic standard. The density of sialic acid residues per cell ranged from 1.6×10 6 to 2.8×10 6. The surface distribution of sialic acids over the entire C. albicans was inferred from labeling with fluorescein- Limulus polyphemus and Limax flavus agglutinins and directly observed by optical microscopy with (FITC)- Sambucus nigra agglutinin (SNA), abrogated by previous treatment of yeasts with bacterial sialidase. Sialidase-treated yeasts generated β-galactopyranosyl terminal residues that reacted with peanut agglutinin. In C. albicans N-acetyl-neuraminic acids are α2,6- and α2,3-linked as indicated by yeast binding to SNA and Maackia amurensis agglutinin. The α2,6-linkage clearly predominated in both strains. We also investigated the contribution of sialic acids to the electronegativity of C. albicans, an important factor determining fungal interactions in vivo. Adhesion of yeast cells to a cationic solid phase substrate (poly- L-lysine) was mediated in part by sialic acids, since the number of adherent cells was significantly reduced after treatment with bacterial sialidase. The present evidence adds C. albicans to the list of pathogenic fungi that synthesize sialic acids, which contribute to the negative charge of fungal cells and have a role in their specific interaction with the host tissue.

Ecology ofCandida-associated Denture Stomatitis

Introduction of a prosthesis into the oral cavity results in profound alterations of the environmental conditions as the prosthesis and the underlying mucosa become colonized with oral microorganisms, including Candida spp. This may lead to denture stomatitis, a non-specific inflammatory reaction against microbial antigens, toxins and enzymes produced by the colonizing microorganisms. The role of Candida in the etiology of denture stomatitis is indicated by an increased number of yeasts on the mucosa and the dentures, increased levels of anti-Candida antibody titres in affected individuals and the clinical improvement of the mucosa due to eradication of the yeast flora. The colonization of the fitting denture surface by Candida depends on several factors including adherence of yeast cells, interaction with oral commensal bacteria, redox potential of the site, and surface properties of the acrylic resin. The pathogenicity of denture plaque can be enhanced by factors stimulating yeast propagation, such as poor oral hygiene, high carbohydrate intake, reduced salivary flow and continuous denture wearing. The more important factors which can modulate the host-parasite relationship and increase the susceptibility to Candida-associated denture stomatitis may be ageing, malnutrition, immunosuppression, radiation therapy, diabetes mellitus, and possibly treatment with antibacterial antibiotics. To control plaque formation on the fitting denture surface and the underlying mucosa it is important to install appropriate oral and denture hygiene measures as well as denture wearing habits. The Candida infection associated with denture stomatitis is a relatively harmless condition in healthy individuals; however, the infection may spread in susceptible individuals.

Identification and cloning of GCA1, a gene that encodes a cell surface glucoamylase from Candida albicans.

Adherence of yeast cells of Candida albicans to human oesophageal cells is greater when cells are grown in 500 mM D-galactose in comparison to D-glucose at the same concentration. Moreover, a 190 kDa mannoprotein (MP190) from a yeast cell wall preparation is highly expressed when cells are grown in the presence of galactose but less so in glucose. We now report on the identification of the MP190 and the isolation of its encoding gene. MP190 was purified, and three internal peptides were isolated and sequenced. Each of the three peptides showed significant homology (65-85%) with a glucoamylase (GAM1) from the yeast, Schwanniomyces occidentalis. In order to isolate the C. albicans homologue of GAM1 (GCA1), we probed a genomic library with a 0.9-kb internal fragment of the S. occidentalis GAM1 and isolated a 2.3-kb clone that corresponded to the 5' region of the gene. Polymerase chain reaction (PCR) amplification was used to isolate the remainder of the open reading frame. GCA1 encodes a 946 amino acid protein containing three putative hydrophobic, membrane-spanning domains and 15 potential N-glycosylation sites. Both Gca1p and GAM1 are novel to the family of glycosyl hydrolases. Northern analysis indicated that GCA1 is transcribed to a greater extent in galactose than in sucrose or glucose. Also, using reverse transcriptase (RT)-PCR, we observed expression of GCA1 in a rat model of oral candidiasis, indicating that Gca1p is expressed during disease development.

High Pressure Freezing/Freeze Substituion: Comparison of Chemical Fixation Versus Cryoimmobilization of Candida Albicans Cultured in Cellulose Tubing

In the interactions of Candida albicans with host cells, the cell wall of the yeast may play important roles in the adhesion of yeast cells to tissues. The outer cell wall of yeast (e.g. Saccharomyces cerevisiae, C. albicans) has been shown to consist of a dense network of radially projecting fibrils composed of mannoproteins that are known as fimbriae and which previously have required cryopreservation either by jet propane freezing or by plunge freezeing for their visualization. High pressure freezing provides an advantage over jet or plunge freezing in terms of the higher consistancey in the quality of freezing, and the minimization of formation of ice I with this method. Hohenberg et al reported a method utilizing cellulose capillary tubes to cryoimmobilize suspensions of microoganisms by high pressure freezing (HPF) and freeze substitution (FS), and herein, we describe an adaptation of this method by culturing microorganisms within the tubing to increase cell density prior to high pressure freezing and freeze substution.

Evidence for alphavbeta3 and alphavbeta5 integrin-like vitronectin (VN) receptors in Candida albicans and their involvement in yeast cell adhesion to VN.

The expression of integrin vitronectin (VN) receptors on Candida albicans yeasts and their involvement in the adhesion to VN were investigated. By immunofluorescence and cytofluorimetric analysis, several antibodies directed against human alphav, beta3, beta5, alphavbeta3, or alphavbeta5 integrin positively stained C. albicans yeasts. Biochemical analysis on yeast lysates with anti-human alphav, beta3, or beta5 antibody revealed molecular species of 130, 110, 100, and 84 kDa. The 130-kDa band was identified as alphav, whereas the doublet of 110/100 kDa and the 84-kDa band likely correspond to the beta3 and beta5 subunits, respectively. Some 48%-54% of Candida yeasts specifically adhered to VN, and this binding was strongly inhibited by anti-human alphav, beta3, alphavbeta3, and alphavbeta5 antibodies and by RGD- but not RGE-containing peptides. In addition, VN inhibited C. albicans adherence to a human endothelial cell line. Thus, C. albicans in the yeast phase expresses VN receptors antigenically related to the vertebrate alphavbeta3 and alphavbeta5 integrins, which mediate its adhesion to VN.

A rapid and selective assay for measuring cell surface hydrophobicity of brewer's yeast cells.

A rapid and selective assay was developed to measure cell surface hydrophobicity of brewer's yeast cells. During this so-called magnobead assay, bottom-fermenting yeast cells adhere to paramagnetic, polystyrene-coated latex beads which can easily be removed from the cell suspension by using a (samarium-cobalt) magnet. At pH 4 center dot 5, electrostatic repulsion between yeast cells and latex beads was found to be minimal and yeast cell adhesion was predominantly based on hydrophobic interactions. The percentage of cells adhering to the beads could be calculated and provided a measure for cell surface hydrophobicity. Cell surface hydrophobicity measured by the magnobead assay was found to yield similar results, as did determination of contact angles of water droplets on a layer of yeast cells, a standard method for measuring surface hydrophobicity. However, the magnobead assay has the following advantages: (i) it is a quick and simple method, and, more significantly, (ii) hydrophobicity can be measured under physiological conditions. Use of the magnobead assay confirmed that a higher level of cell surface hydrophobicity is correlated with stronger flocculence of brewer's lager yeast cells.