Schenckii Cell Research Articles

Immunization with recombinant enolase of Sporothrix spp. (rSsEno) confers effective protection against sporotrichosis in mice

In recent years, research has focused on the immunoreactive components of the Sporothrix schenckii cell wall that can be relevant targets for preventive and therapeutic vaccines against sporotrichosis, an emergent worldwide mycosis. In a previous study, we identified a 47-kDa enolase as an immunodominant antigen in mice vaccinated with an adjuvanted mixture of S. schenckii cell wall proteins. Here, we sought to assess the protective potential of a Sporothrix spp. recombinant enolase (rSsEno) formulated with or without the adjuvant Montanide Pet-GelA (PGA) against the S. brasiliensis infection in mice. Mice that were immunized with rSsEno plus PGA showed increased antibody titters against rSsEno and increased median survival time when challenged with S. brasiliensis as compared with mice that had not been immunized or that were immunized with rSsEno alone. Immunization with rSsEno plus PGA induced a predominantly T-helper 1 cytokine pattern after in vitro stimulation of splenic cells with rSsEno: elevated levels of IFN-γ and IL-2, as well as of other cytokines involved in host defense against sporotrichosis, such as TNF-alpha, IL-6, and IL-4. Furthermore, we show for the first time the presence of enolase in the cell wall of both S. schenckii and S. brasiliensis. As a whole, our results suggest that enolase could be used as a potential antigenic target for vaccinal purposes against sporotrichosis.

Morphological changes and phagocytic activity during the interaction of human neutrophils with Sporothrix schenckii: An in vitro model

Histopathological studies of human sporotrichosis lesions show pyogenic and granulomatous processes in which polymorphonuclear neutrophils (PMNs) play a central role. Few studies regarding the events associated with the interaction of human PMNs with Sporothrix schenckii have been made despite their importance in the clinical manifestations of the disease. In this study, human PMNs were co-cultured with conidia or yeast cells of S. schenckii to compare the phagocytic activity and morphological changes that could provide a clearer insight into the role of these phagocytes in the initial phase of sporotrichosis. PMNs showed increased cell size and separation of the nuclear lobes after phagocytosis. Through Scanning Electron Microscopy (SEM) analysis, an increase in cells with flattened filaments and vesicles on their surface was observed. Phagocytosed conidia showed a significant increase in width and size. The phagocytic activity was greater against yeasts than with conidia, but the viability of both S. schenckii cellular morphotypes was not drastically affected even after 2 h of co-culture. In conclusion, morphological changes in PMNs suggest that S. schenckii induces processes that may favor proinflammatory events. These phagocytes show a high ability to bind or ingest S. schenckii cells without affecting their viability. Morphological changes recorded in ingested conidia, suggest that this fungus could make the dimorphic switching in PMNs.

Dectin-1 expression by macrophages and related antifungal mechanisms in a murine model of Sporothrix schenckii sensu stricto systemic infection.

The available information about the role of Dectin-1 in sporotrichosis is scarce. Hence, we aimed to assess Dectin-1 expression by macrophages and the activation of some related antifungal mechanisms during the Sporothrix schenckii sensu stricto infection as a first attempt to elucidate the role of this receptor in sporotrichosis. Balb/c mice were intraperitoneally infected with S.schenckii sensu stricto yeast ATCC 16345 and euthanized on days 5, 10 and 15 post-infection, when the following parameters were evaluated: fungal burden in spleen, Dectin-1 expression and nitric oxide (NO) production by peritoneal macrophages, as well as IL-1β, TNF-α and IL-10 exvivo secretion by these same cells. Peritoneal macrophages were exvivo challenged with either the alkali-insoluble fraction (F1) extracted from the S.schenckii cell wall, a commercially available purified β-1,3-glucan or whole heat-killed S.schenckii yeasts (HKss). Additionally, a Dectin-1 antibody-mediated blockade assay was performed on day 10 post-infection to assess the participation of this receptor in cytokine secretion. Our results showed that Dectin-1 expression by peritoneal macrophages was augmented on days 10 and 15 post-infection alongside elevated NO production and exvivo secretion of IL-10, TNF-α and IL-1β. The antibody-mediated blockade of Dectin-1 inhibited cytokine production in both infected and non-infected mice, mainly after β-1,3-glucan stimulation. Our results suggest a role for Dectin-1 in triggering the immune response during S.schenckii infection.

Adamantylidene-substituted alkylphosphocholine TCAN26 is more active against Sporothrix schenckii than miltefosine.

Sporotrichosis is the most frequent subcutaneous mycosis in the world and its increasing incidence has led to the search for new therapeutic options for its treatment. In this study, we demonstrated that three structural analogues of miltefosine (TCAN26, TC19, and TC70) showed inhibitory activity against Sporothrix schenckii sensu stricto and that TCAN26 was more active in vitro than miltefosine against several isolates. Scanning electron microscopy showed that S. schenckii exposure to TCAN26 resulted in cells that were slightly more elongated than untreated cells. Transmission electron microscopy showed that TCAN26 treatment induced loss of the regular cytoplasmic electron-density and altered the cell envelope (disruption of the cell membrane and cell wall, and increased cell wall thickness). Additionally, TCAN26 concentrations required to kill S. schenckii cells were lower than concentrations that were cytotoxic in mammalian cells, and TCAN26 was more selective than miltefosine. Thus, the adamantylidene-substituted alkylphosphocholine TCAN26 is a promising molecule for the development of novel antifungal compounds, although further investigations are required to elucidate the mode of action of TCAN26 in S. schenckii cells.

A cell wall protein-based vaccine candidate induce protective immune response against Sporothrix schenckii infection

Sporotrichosis is a subcutaneous mycosis caused by several closely related thermo-dimorphic fungi of the Sporothrix schenckii species complex, affecting humans and other mammals. In the last few years, new strategies have been proposed for controlling sporotrichosis owning to concerns about its growing incidence in humans, cats, and dogs in Brazil, as well as the toxicity and limited efficacy of conventional antifungal drugs. In this study, we assessed the immunogenicity and protective properties of two aluminum hydroxide (AH)-adsorbed S. schenckii cell wall protein (ssCWP)-based vaccine formulations in a mouse model of systemic S. schenckii infection. Fractioning by SDS-PAGE revealed nine protein bands, two of which were functionally characterized: a 44kDa peptide hydrolase and a 47kDa enolase, which was predicted to be an adhesin. Sera from immunized mice recognized the 47kDa enolase and another unidentified 71kDa protein, whereas serum from S. schenckii-infected mice recognized both these proteins plus another unidentified 9.4kDa protein. Furthermore, opsonization with the anti-ssCWP sera led to markedly increased phagocytosis and was able to strongly inhibit the fungus’ adhesion to fibroblasts. Immunization with the higher-dose AH-adjuvanted formulation led to increased ex vivo release of IL-12, IFN-γ, IL-4, and IL-17, whereas only IL-12 and IFN-γ were induced by the higher-dose non-adjuvanted formulation. Lastly, passive transference of the higher-dose AH-adjuvanted formulation's anti-ssCWP serum was able to afford in vivo protection in a subsequent challenge with S. schenckii, becoming a viable vaccine candidate for further testing.

Sporothrix schenckii(sensu strictS. globosa) mating type 1-2 (MAT1-2) gene

Sporotix schenckii is a pathogenic fungus that causes human and animal sporotrichosis, and based on morphology of the sessile conidia and molecular analysis, it was recently recognized as a species complex comprising at least the following six sibling species: S.albicans, S.brasiliensis, S.globosa, S.luriei, S.mexicana and S.schenckii. However, apart from S.schenckii sensu strict, only S.brasiliensis, S.globosa and S.luriei are associated with human and animal infection. S.globosa has been most commonly isolated in Asia, Europe and the USA; therefore, molecular epidemiological study for S.globosa is important in relation to human sporotrichosis in Japan. To the best of our knowledge, this is the first study to determine the mating type 1-2 (MAT1-2) gene of Sporothrix schenckii with the aim of understanding the taxonomy of the genus Sporothrix. The MAT1-2 gene (1618bp) encodes a protein sequence of 198 amino acids. Reverse transcription polymerase chain reaction analysis also detected MAT1-2 gene mRNA expression in all of the S.schenckii strains examined, indicating that this gene is expressed in S.schenckii cells. Phylogenetic analysis of the MAT1-2 gene fragments of Ophiostoma himal-ulmi, O.novo-ulmi, O.ulmi and S.schenckii indicated that these isolates could be classified into four clusters. MAT1-1 gene-specific polymerase chain reaction was positive in 15 isolates, but negative in four human isolates and one feline isolate.

Epidemiological Findings and Laboratory Evaluation of Sporotrichosis: A Description of 103 Cases in Cats and Dogs in Southern Brazil

Sporotrichosis is a subcutaneous mycosis, which affects mainly small animals, and is considered an important public health disease. This paper describes the epidemiological and laboratory characteristics of 103 clinical cases of sporotrichosis diagnosed over a 10-year period in southern Brazil. The 92 cats and 11 dogs from eight municipalities in Rio Grande do Sul State developed especially the disseminated cutaneous and fixed cutaneous forms of the disease. Respiratory signs such as sneezing, serous nasal discharge and dyspnea were found in about 57% of the animals. The detection of Sporothrix schenckii in different clinical samples showed highest isolation in testicles (46.6%), oral cavity (45.2%) and conjunctival mucosa (38.1%). A differentiated histological pattern was found between the fixed cutaneous and disseminated cutaneous (DC) manifestations of the disease; well-organized granulomas of nodular distribution and various fungal structures prevailed in the DC form in cats. Melanin detection in S. schenckii cells by the Fontana-Masson technique was positive in 45.4% of the samples. The study revealed that the State of Rio Grande do Sul is an endemic sporotrichosis area and demonstrated the possibility of involvement of other pathways in the infection and spread of the disease. In addition, it emphasized the importance of laboratory tests for mycosis confirmation, especially in dogs that develop clinical manifestations without the presence of cutaneous lesions.

2D-immunoblotting analysis of Sporothrix schenckii cell wall

We utilized two-dimensional gel electrophoresis and immunoblotting (2D-immunoblotting) with anti-Sporothrix schenckii antibodies to identify antigenic proteins in cell wall preparations obtained from the mycelial and yeast-like morphologies of the fungus. Results showed that a 70-kDa glycoprotein (Gp70) was the major antigen detected in the cell wall of both morphologies and that a 60-kDa glycoprotein was present only in yeast-like cells. In addition to the Gp70, the wall from filament cells showed four proteins with molecular weights of 48, 55, 66 and 67 kDa, some of which exhibited several isoforms. To our knowledge, this is the first 2D-immunoblotting analysis of the S. schenckii cell wall.

Sporothrix Schenckii Complex And Sporotrichosis, An Emerging Health Problem

Sporothrix schenckii, now named the S. schenckii species complex, has largely been known as the etiological agent of sporotrichosis, which is an acute or chronic subcutaneous mycosis of humans and other mammals. Gene sequencing has revealed the following species in the S. schenckii complex: Sporothrix albicans, Sporothrix brasiliensis, Sporothrix globosa, Sporothrix luriei, Sporothrix mexicana and S. schenckii. The increasing number of reports of Sporothrix infection in immunocompromised patients, mainly the HIV-infected population, suggests sporotrichosis as an emerging global health problem concomitant with the AIDS pandemic. Molecular studies have demonstrated a high level of intraspecific variability. Components of the S. schenckii cell wall that act as adhesins and immunogenic inducers, such as a 70-kDa glycoprotein, are apparently specific to this fungus. The main glycan peptidorhamnomannan cell wall component is the only O-linked glycan structure known in S. schenckii. It contains an α-mannobiose core followed by one α-glucuronic acid unit, which may be mono- or di-rhamnosylated. The oligomeric structure of glucosamine-6-P synthase has led to a significant advance in the development of antifungals targeted to the enzyme's catalytic domain in S. schenckii.

Cell surface expression of adhesins for fibronectin correlates with virulence in Sporothrix schenckii

The virulence of four Sporothrix schenckii isolates was compared in a murine model of sporotrichosis, together with the protein pattern of the yeast cell surface and the capacity to bind the extracellular matrix protein fibronectin. Virulence was determined by the mortality rate, fungal burden and histopathology. Two clinical isolates were more virulent for C57BL/6 mice, but no direct correlation was seen between virulence and the clinical or environmental origin of the isolates. The lowest virulence was observed for an isolate recovered from a patient with meningeal sporotrichosis. Although all isolates could effectively disseminate, the dissemination patterns were not similar. Using flow cytometry analysis, we investigated the interaction of all the strains with fibronectin, and showed that the binding capacity correlated with virulence. Western blot analysis of S. schenckii cell wall extracts revealed positive bands for fibronectin in the range of 37-92 kDa. The 70 kDa adhesin was also recognized by a protective monoclonal antibody raised against a gp70 antigen of S. schenckii (mAb P6E7). Confocal microscopy confirmed the co-localization of fibronectin and mAb P6E7 on the yeast cell surface. To our knowledge, this is the first report identifying adhesins for fibronectin on the surface of this human pathogen.

Efficacy of terbinafine and itraconazole on a experimental model of systemic sporotrichosis

Itraconazole is currently considered the drug of choice to treat the diverse clinical presentation of sporotrichosis. On the other hand terbinafine by virtue of its excellent in vitro activity is under comparative evaluation for its therapeutic potential for a wide range of fungal infections. In this study, our aim was to determine the in vivo efficacy of terbinafine and itraconazole on a experimental model of systemic sporotrichosis. 120 rats Wistar received an injection of 2×10(3) S. schenckii cells by via the lateral tail vein. After 3 days the animals were treated with terbinafine (250mg/kg) and itraconazole (100 mg/kg) and their respective diluents. In our model, terbinafine and itraconazole were effective in reducing the number of clinical lesions and positive organ cultures. There was statistical difference between the groups treated with the antifungals in relation to the control groups (p<0,05) concerning the clinical alterations, anatomic-pathological findings and in the positive organ cultures of the agent, being that the treated animals resulted in the absence and/or reduction of all the evaluated parameters. As for the treatments, terbinafine showed similar or higher activity that itraconazole in the evaluation of the testicle alteration (p=0,0004), as well as in the positive organ cultures of microorganism from the organ (p=0,0142). With these results it is possible to conclude that the antifungals studied are effective in the treatment of experimental systemic sporotrichosis.

Efficacy of terbinafine and itraconazole on a experimental model of systemic sporotrichosis

Itraconazole is currently considered the drug of choice to treat the diverse clinical presentation of sporotrichosis. On the other hand terbinafine by virtue of its excellent in vitro activity is under comparative evaluation for its therapeutic potential for a wide range of fungal infections. In this study, our aim was to determine the in vivo efficacy of terbinafine and itraconazole on a experimental model of systemic sporotrichosis. 120 rats Wistar received an injection of 2×103 S. schenckii cells by via the lateral tail vein. After 3 days the animals were treated with terbinafine (250mg/kg) and itraconazole (100 mg/kg) and their respective diluents. In our model, terbinafine and itraconazole were effective in reducing the number of clinical lesions and positive organ cultures. There was statistical difference between the groups treated with the antifungals in relation to the control groups (p<0,05) concerning the clinical alterations, anatomic-pathological findings and in the positive organ cultures of the agent, being that the treated animals resulted in the absence and/or reduction of all the evaluated parameters. As for the treatments, terbinafine showed similar or higher activity that itraconazole in the evaluation of the testicle alteration (p=0,0004), as well as in the positive organ cultures of microorganism from the organ (p=0,0142). With these results it is possible to conclude that the antifungals studied are effective in the treatment of experimental systemic sporotrichosis.

The in vitro interaction of Sporothrix schenckii with human endothelial cells is modulated by cytokines and involves endothelial surface molecules

Sporothrix schenckii is the etiological agent of sporotrichosis, a subcutaneous mycosis that can evolve to systemic complications in immunocompromised patients. Interactions with endothelium are thought to be essential for systemic infections. In the present work, we studied the interaction between S. schenckii and human umbilical vein endothelial cells (HUVECs). S. schenckii interacts with HUVECs in a time-dependent manner. Morphological analysis showed that yeasts locate to interendothelial junctions. Ultrastructural studies showed that internalized yeasts were found inside endocytic vacuoles as early as 2 h, without causing any detectable damage to HUVECs after 24 h of infection. The viability of infected HUVECs was confirmed by the MTT assay. When HUVECs were treated with different concentrations of Interleukin-1β or transforming growth factor-beta, a significant dose-dependent increase in cell-associated yeasts was observed. The preliminary analysis of the endothelial surface ligands for S. schenckii cells revealed two major molecules, with M r of ≈90 and 135 kDa. The interaction of endothelial cell surface molecules with S. schenckii yeast cells was modulated by divalent cations. This is the first demonstration that S. schenckii is able to adhere and invade endothelial cells without significantly affect cellular integrity. Our results suggest the contribution of cytokine-modulated calcium-dependent molecules to this process.

Concanavalin A-binding cell wall antigens ofSporothrix schenckii: a serological study

Sporothrix schenckii cell wall peptido-rhamnomannan (CWPR) was fractionated by affinity chromatography on Sepharose 4B-Concanavalin A giving rise to S. schenckii concanavalin A-binding (SsCBF) and nonbinding (SsNBF) fractions. The CWPR, SsCBF and SsNBF fractions were probed by enzyme-linked immunosorbent assay (ELISA) with the sera of 35 patients with sporotrichosis from Latin America. Both CWPR and SsNBF, although reacting with sera from patients with sporotrichosis, were also cross-reactive with sera from healthy individuals and from patients with other mycoses. In contrast, SsCBF was shown to react specifically with 100% of the sera from patients with sporotrichosis, compared with control sera and sera from patients with other mycoses or cutaneous leishmaniasis. This antigenic fraction was submitted to mild alkaline hydrolysis to remove O-glycosidically linked oligosaccharides and the resulting components had decreased reactivity with patients' sera. The purified SsCBF-derived O-linked pentasaccharide and tetrasaccharide were potent inhibitors of, respectively 76 and 53% of the reaction between SsCBF and sera from patients with sporotrichosis. Our results suggest that SsCBF is a species-specific antigenic fraction recognized by human sera and that this specificity correlates with the presence of O-linked mannose-containing oligosaccharides decorated with the alpha-L-Rha 1-->4 alpha-D-GlcA and alpha-L-Rha 1-->4 [alpha-L-Rha 1-->2] alpha-D-GlcA epitope structures previously described [1].

Identification of a concanavalin A-binding antigen of the cell surface of Sporothrix schenckii.

Sporothrix schenckii (1099-18) cell wall peptido-rhamnomannan (CWPR) was fractionated by affinity chromatography with Concanavalin A. The Con A-bound and Con A-unbound fractions were probed with an anti-S. schenckii rabbit serum. We identified within the Con A-bound fraction three main antigens with approximate molecular weights of 84, 70 and 58 kDa. Glycopeptide beta-elimination reduced rabbit antiserum reactivity for the 84 kDa antigen (gp84) with concomittant enhanced reactivity for the 70 kDa antigen (gp70). By Western blot with Con A-HRP conjugate we demonstrated that gp84 strongly reacted with this lectin and this was the predominant antigen identified. The gp84 antigen was also demonstrated to be present on other S. schenckii strains.

Acid phosphatases of Sporothrix schenckii.

Sporothrix schenckii cells were grown on a medium containing yeast extract, neopeptone and glucose at 20 degrees C to obtain a mixture of mycelia and conidia, and at 35 degrees C to obtain yeast-like cells. The organism was maintained in the mycelial form, and its transformation to yeast at the higher temperature proceeded via conidia and 'intermediate cells' that then gave rise to yeast by a blastic mechanism. Cell-free extracts were analysed by PAGE at pH 8.0 and acid phosphatases (EC 3.1.3.2) were revealed by a sensitive detection reagent at pH 5.0. Mycelial, conidial and yeast extracts all had some acid phosphatase activity (M-I, C-I and Y-I) at the origin, although the proportion was highest for the yeast extracts. All of the bands that penetrated the gels had different electrophoretic mobilities. Mycelial and conidial extracts each had one other isoenzyme (M-II and C-II), while the yeast extracts had a total of five electrophoretically distinct acid phosphatases. Isoenzyme Y-II was further resolved into five closely related bands (Y-IIa to Y-IIe), the relative intensities of which varied with the phosphate nutrition of the yeast cells and the history of the extracts. The acid phosphatase isoenzymes were inhibited to various extents by sodium fluoride, L(+)-tartrate and phosphate, and showed interactions with citrate as opposed to acetate as the background buffer at pH 5.0.

Galactose-reacting agglutinins to Sporothrix schenckii.

ABSTRACTAgglutinins to Sporothrix schenckii were produced in rabbits by immunization with Aspergillus fumigatus. Agglutination of S. schenckii cells was inhibited by D‐galactose but not by D‐mannose. Indirect immuno‐scanning electron microscopy using rabbit anti‐A. fumigatus serum and ferritin conjugated goat anti‐rabbit IgG serum showed considerable labelling of ferritin particles at the cell surface of S. schenckii; this behavior was inhibited by D‐galactose but not D‐mannose. These results suggested that galactose determinants were present at the cell surface of S. schenckii and that agglutinins to S. schenckii were divided into two groups, galactose‐reacting antibodies as well as the already recognized rhamnose‐reacting ones.

Ingestion of yeast forms of Sporothrix schenckii by mouse peritoneal macrophages.

The ingestion by thioglycolate-elicited mouse peritoneal macrophages of yeast forms of two strains of Sporothrix schenckii was studied. Yeast forms opsonized with concanavalin A (ConA) were extensively phagocytized, and the phagocytic indexes depended on the concentration of ConA and apparently on the number of lectin receptors at the yeast surface as well. Neuraminidase treatment of S. schenckii increased the ingestion of unopsonized yeasts 7.7-fold. The addition of monosaccharides and derivatives partially inhibited phagocytosis. Mannose, rhamnose, and galactose, which are major constituents of S. schenckii surface antigens, reduced the phagocytic indexes by 40 to 50%. Glucosamine, N-acetylglucosamine, and N-acetylneuraminic acid were equally effective as inhibitors of phagocytosis. A mixture of five neutral sugars and glucosamine inhibited phagocytosis by 73%. The inhibitory effect of simple sugars could be amplified by using neuraminidase-treated yeast cells. Pentoses and glucose were inactive or slightly inhibitory. A purified rhamnomannan inhibited phagocytosis of the homologous strain, whereas partially purified peptidopolysaccharides were toxic to peritoneal macrophages. A partially purified galactomannan from S. schenckii was inhibitory (62% inhibition), and a peptidopolysaccharide fraction in which the O-linked carbohydrate chains had been removed neither was toxic to macrophages nor inhibited phagocytosis. Pretreatment of macrophages with simple sugars under conditions inhibiting ingestion or binding of S. schenckii did not affect phagocytosis of latex particles or sensitized sheep erythrocytes. The presence of receptors at the peritoneal macrophages which bind S. schenckii cell surface components is suggested.

Distribution of anionic groups at the cell surface of different Sporothrix schenckii cell types.

The distribution of anionic groups at the cell surface of yeastlike forms, hyphae, and conidia of Sporothrix schenckii was studied by staining with colloidal iron hydroxide and cationized ferritin. By using colloidal iron hydroxide it was shown that the external cell wall layer of one strain (strain 1099.18) could be resolved into two reactive sublayers and that these layers were present in many but not all cells of the same population. In contrast, most cells of another strain (strain 1099.12) were stained by colloidal iron hydroxide, but only one reactive layer was seen. Acidic layers of the yeastlike forms of the two strains were much thicker than those of conidia and hyphae. By the cationized ferritin staining procedure it was observed that the acidic layers of yeast forms sloughed off of cells, probably due to cell-cell or cell-medium attrition in shaken submerged cultures or to a process by which the outer layers detach from cells as they are replaced by newly synthesized ones. The colloidal iron hydroxide- and cationized ferritin-reactive cell surface layers of S. schenckii correspond to the previously described (L. R. Travassos et al., Exp. Mycol. 1:293-305, 1977) concanavalin A-reactive peptidorhamnomannan complexes, and their reactivity is probably due to the presence of acidic amino acids of low pK values rather than to glucuronic acid units.

Distribution of antigenic polysaccharides in different cell types of Sporothrix schenckii as studied by immunofluorescent staining with rabbit antisera

Immunofluorescent staining was used to locate surface antigens in different Sporothrix schenckii cell types. An antiserum specific for monorhamnosyl rhamnomannans reacted strongly with yeasts, yeast primordia on the hyphae, and conidia of three strains of S. schenckii . Another antiserum specific for dirhamnosyl rhamnomannans reacted well with the hyphae and poorly or irregularly with the other cell types. Variations in this pattern were observed in some instances and were interpreted as being due to the presence of both antigens in the particular cell type, to differences in the amount of antigens in different cells, or to a limited cross-reactivity of the antisera with rhamnose-containing polymers exposed on the cell surface. These results on the in situ demonstration of different rhamnomannans in the various cell types of S. schenckii are in general agreement with studies on the structures of the isolated polysaccharides.