Tomoe Ichikawa

Two new yeasts, Trichosporon debeurmannianum sp. nov. and Trichosporon dermatis sp. nov., transferred from the Cryptococcus humicola complex

Cryptococcus humicola, as currently defined, shows intraspecific rRNA gene sequence differences. Three strains of this species produced arthroconidia on cornmeal agar and belonged to the genus Trichosporon in a molecular phylogeny. They clustered with the species possessing Q10 as the major ubiquinone and were serotype I. Sequence analyses clearly revealed that they were two new Trichosporon species. The names Trichosporon dermatis sp. nov. (= CBS 2043T) and Trichosporon debeurmannianum sp. nov. (= CBS 1896T) are proposed for these strains.

Phenotypic switching and β-N-acetylhexosaminidase activity of the pathogenic yeast Trichosporon asahii

The pathogenic yeast Trichosporon asahii is the major causative agent of deep‐seated trichosporonosis in immunocompromised patients. Although infection by this microorganism is becoming increasingly frequent, information related to its pathogenicity and virulence factors is still limited. Therefore, we investigated phenotypic switching in colony morphology, and the production of extracellular enzymes as a virulence factor. Sixty‐one clinical isolates of T. asahii produced four different morphological types on Sabouraud dextrose agar (SDA): 69% WF (white farinose), 18% WP (white pustular), 10% Y (yellowish white), and 3% WC (white cerebriform). Strains of the three major types (WF, WP, and Y) produced two to five colony types when cultured on SDA at 37 C. The frequency of switching between colony types was 10–2 to 10–4, as in Candida albicans and Cryptococcus neoformans. Notably, most of the colonies switched to the smooth (S) type irreversibly, at frequencies of 10–2 to 10–3. No secreted aspartic proteinase or phospholipase activity was detected in T. asahii, while β‐N‐acetylhexosaminidase activity, which catalyzes the hydrolysis of terminal nonreducing N‐acetyl‐D‐hexosamine residues in N‐acetyl‐β‐D‐hexosaminides, was found. Furthermore, enzymatic activity of the S type was significantly greater than that of the parent type in all strains. No other clinically relevant Trichosporon species (T mucoides, T inkin, and T ovoides) produced this enzyme. These results provide basal information for understanding the pathogenic potential of T asahii.

Multilocus sequence typing analysis reveals that Cryptococcus neoformans var. neoformans is a recombinant population

Cryptococcus neoformans var. neoformans (serotype D) represents about 30% of the clinical isolates in Europe and is present less frequently in the other continents. It is the prevalent etiological agent in primary cutaneous cryptococcosis as well as in cryptococcal skin lesions of disseminated cryptococcosis. Very little is known about the genotypic diversity of this Cryptococcus subtype. The aim of this study was to investigate the genotypic diversity among a set of clinical and environmental C. neoformans var. neoformans isolates and to evaluate the relationship between genotypes, geographical origin and clinical manifestations. A total of 83 globally collected C. neoformans var. neoformans isolates from Italy, Germany, France, Belgium, Denmark, Greece, Turkey, Thailand, Japan, Colombia, and the USA, recovered from different sources (primary and secondary cutaneous cryptococcosis, disseminated cryptococcosis, the environment, and animals), were included in the study. All isolates were confirmed to belong to genotype VNIV by molecular typing and they were further investigated by MLST analysis. Maximum likelihood phylogenetic as well as network analysis strongly suggested the existence of a recombinant rather than a clonal population structure. Geographical origin and source of isolation were not correlated with a specific MLST genotype. The comparison with a set of outgroup C. neoformans var. grubii isolates provided clear evidence that the two varieties have different population structures.

Structural studies of the antigen III cell wall polysaccharide of Trichosporon domesticum.

Cell wall and soluble polysaccharides that reacted with Trichosporon domesticum factor III serum were isolated from the type strain of T. domesticum. The fractions contained O-acetyl groups, which contributed to the serological reactivity. The antigenic structure was characterized by chromatographic and spectroscopic methods. The polysaccharide has an alpha-(1-->3)-D-mannan backbone with hetero-oligosaccharide side chains consisting of a 2-O-substituted beta-D-glucuronic acid residue bound to O-2 of the mannose residue, beta-D-xylopyranosyl residues located in the middle of the side chain, and a nonreducing terminal alpha-L-arabinopyranosyl residue bound to 0-4 of xylose. The mannan backbone is O-acetylated at O-6 of the mannose residues.

Interaction of surface molecules on Cryptococcus neoformans with plasminogen

Microbial pathogens are known to express molecules that interact with host proteins, leading to invasion and colonization. For example, some pathogenic microorganisms express proteins that bind to and enhance the activity of plasminogen. In this way, pathogens utilize the host fibrinolytic system to promote invasion. We found that triosephosphate isomerase (TPI), a glycolytic enzyme produced by Staphylococcus aureus, bound to mannooligosaccharides from the pathogenic capsulated fungus Cryptococcus neoformans and human plasminogen, suggesting that TPI is a moonlighting protein. Several C. neoformans surface proteins are thought to be plasminogen-binding proteins. Here, we examined the ability of surface polymers (including polysaccharides) to bind plasminogen. Heat-killed C. neoformans cells transformed plasminogen into plasmin in a dose-dependent manner in the presence of tissue plasminogen activator. Soluble polysaccharides were found to bind plasminogen based on surface plasmon resonance (SPR) analysis. Neutral polysaccharides fractionated using DEAE column chromatography bound and activated plasminogen. However, the fraction containing glucuronoxylomannan (the primary component of the capsule) did not activate plasminogen. In addition, binding between glucuronoxylomannan and plasminogen was weak. Components of the neutral polysaccharides were identified as mannose, galactose, glucose and xylose. In conclusion, neutral polysaccharides that may affect fibrinolysis were detected on the surface of C. neoformans.

Cell surface hydrophobicity and colony morphology of Trichosporon asahii clinical isolates

Trichosporon asahii is a pathogenic basidiomycetous yeast. Individual strains of T. asahii have different colony morphologies. However, it is not clear whether cell surface phenotypes differ among the colony morphologies. Here we characterized the cell surface hydrophobicity and analysed the carbohydrate contents of the cell surface polysaccharides in T. asahii clinical isolates with various colony morphologies. Among the three distinctive colony morphologies obtained from one clinical isolate, the white‐type morphology exhibited higher hydrophobicity. The hydrophobicity of heat‐killed T. asahii cells was greatly reduced after periodate oxidation of the cell surface carbohydrates. Furthermore, the cell wall and extracellular polysaccharide components differed among the morphologies. Our results suggest that T. asahii cell surface hydrophobicity is affected by cell surface carbohydrate composition. Copyright

Switching of colony morphology and adhesion activity of Trichosporon asahii clinical isolates.

Trichosporon asahii is a pathogenic yeast that causes trichosporonosis, a deep-seated infection, in immunocompromised hosts. Pathogenic factors involved in this infection have not been investigated in detail, but morphological phenotype switching is thought to be important for T. asahii pathogenesis. Therefore, we analyzed adhesion, which may be a key early step in T. asahii infection, after morphological phenotype switching. T. asahii clinical isolates show several colony morphologies. In this study, colonies showing white-farinose (W), off-white-smooth (O), off-white-rugose (OR), smooth (S), and yellowish-white (Y) morphologies were obtained from three isolates and compared in an adhesion assay performed in cell culture dishes. At least one type of colony morphology from each clinical isolate adhered strongly to the culture dish surface, although the colony type that displayed strong adherence varied among the strains. Thus, morphological phenotype switching altered the adhesion of T. asahii strains.

Draft Genome Sequence of the Causative Antigen of Summer-Type Hypersensitivity Pneumonitis, Trichosporon domesticum JCM 9580

ABSTRACT Here, we report the draft genome sequence of Trichosporon domesticum JCM 9580, isolated from the house of a patient with summer-type hypersensitivity pneumonitis (SHP) in Japan. This genomic information will help elucidate the mechanisms of the development of SHP.

Comparative Analysis of Extracellular Polymeric Substances from Cryptococcus gattii VGIIa Strain Isolated for the First Time in Japan

Cryptococcus gattii and C. neoformans are pathogenic yeasts that cause meningoencephalitis. C. gattii has four molecular types: VGI, VGII, VGIII, and VGIV. Furthermore, three genotypes have been reported for VGII, and a high pathogenicity of the VGIIa genotype has been proposed. The VGIIa strain has been isolated from a patient in Japan, but little is known about the characteristics of the polysaccharides in this strain. In this study we examined the induction of interleukin-8（IL-8）transcriptional activation and compared the nuclear magnetic resonance（NMR）spectra of extracellular polymeric substances（EPSs）, mainly polysaccharides, from the VGIIa, VGIIb, and VGIIc genotypes. The induction of IL-8 by C. gattii EPSs was weaker than that by C. neoformans EPSs. The anomeric proton signals in the NMR spectra of EPSs obtained from VGII isolates were similar, and the polysaccharides were mainly mannose, xylose, galactose, and glucuronic acid. These results suggest that the extracellular polysaccharides from the VGIIa strain isolated in Japan are almost the same as those from other VGII strains.

Identification of Heparin-binding Proteins on the Cell Surface of Cryptococcus neoformans

Interactions between virulence factors of pathogens and host responses play an important role in the establishment of infection by microbes. We focused on interactions between Cryptococcus neoformans proteins and heparin, which is abundant on host epithelial cells. Surface proteins were extracted and analyzed. Fractions from anion-exchange column chromatography interacted with heparin in surface plasmon resonance analyses. Heparin-binding proteins were purified and then separated by gel electrophoresis; and were identified as transaldolase, glutathione-disulfide reductase, and glyoxal oxidase. These results imply that multifunctional molecules on C. neoformans cells, such as those involved in heparin binding, may play roles in adhesion that trigger responses in the host.