Sporothrix schenckii
A Microbial Biorealm page on the genus Sporothrix schenckii
When drinking wine amongst the roses Or guzzling beer while throwing bricks Or playing games in bales of hay Where lurks the tricky sporothrix, Beware, the price you pay for play, When you get struck by dread mycoses -S. Vaisrub
Classification(1)
Higher order taxa
cellular organisms; Eukaryota; KINGDOM: Fungi/Metazoa group; Fungi; Dikarya; PHYLUM: Ascomycota; SUBDIVISION: Pezizomycotina; CLASS: Sordariomycetes; SUBCLASS: Sordariomycetidae; ORDER: Ophiostomatales; FAMILY: Ophiostomataceae; mitosporic Ophiostomataceae; GENUS: Sporothrix
Species
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NCBI: Taxonomy |
Sporothrix schenckii
Description and significance
Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.
Sporothrix is a thermally dimorphic fungus which is distributed worldwide and isolated from soil, living and decomposing plants, woods, and peat moss. The genus Sporothrix contains one active species, Sporothrix schenckii Sporothrix schenckii is an occasional cause of human infections. Sporothrix schenckii is the pathogenic species. Macroscopic and microscopic features of these species are different from each other. The nonpathogenic Sporothrix sp. may occasionally convert to a yeast phase at 37°C (2). In mammalian tissues, S. schenckii is yeast-like, appearing as spherical or cigar-shaped bodies measuring 4 to 6 μm in length that reproduce by budding. (3)
Genome structure
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
capsular stains prepared by the Muir method indicate the presence of what is interpreted as a distinct capsular-slime layer about the cells, although the material identified as a capsular-slime layer envelope is more profuse about the ovoid type cell than that observed for the elongated fusiform cell. The cell wall measures from approximately 100 to 300 nm in total thickness and appears to be present in two distinct electron-dense layers. Multiple storage granules are noted scattered throughout the cytoplasm along with cell membrane- associated intracytoplasmic membranes. These membranes consist of circular, three-layered, electron-dense structures which clearly communicate with the cell membrane. Seen over the entire outer surface of the cell wall are electron-dense microfibrils which are intimately associated with the cell wall. These microfibrils are long and intertwining. The outer limit of the cytoplasm is the plasma membrane which has the characteristics of a "unit membrane". Microfibrils and the layering effect of the cell wall are prominent. The cell wall is thinner in the mycelial phase than in the yeastlike phase, and was never observed to show the electron-dense microfibrils characteristically seen in yeastlike phase preparations. (5)
The lipid compound of the cell wall plays an important role in the pathogenesis of this mycosis and was found to inhibit the phagocytic process and to induce high liberation of nitric oxide. S. schenckii form some polysaccharides which are firmly bound to the cell wall and some polysaccharides which are released into the medium. These polysaccharides are usually associated with peptide components in the form of covalent complexes in which the carbohydrate part represents about 85% of the total. Soluble and insoluble polysaccharides and their complexes participate in building the structural complex of the cell wall. (4)
Metabolism All fungi are free living, i.e., they are not obligate intracellular parasites. They do not contain chlorophyll and cannot synthesize macromolecules from carbon dioxide and energy derived from light rays. Therefore all fungi are heterotrophs, living on preformed organic matter. For medical purposes the important aspects of fungal metabolism are: The synthesis of chitin, a polymer of N-acetyl glucosamine, and other compounds, for use in forming the cell wall. These induce immune hypersensitivity. The synthesis of ergosterol for incorporation into the plasma membrane. This makes the plasma membrane sensitive to those antimicrobial agents which either block the synthesis of ergosterol or prevent its incorporation into the membrane or bind to it, e.g. amphotericin B. The synthesis of toxins such as: Ergot alkaloids- these are produced by Claviceps purpurea and cause an alpha adrenergic blockade. Psychotropic agents - these include psilocybin, psilocin and lysergic acid diethylamide (LSD). Aflatoxins - these are carcinogens produced by Aspergillus flavus when growing on grain. When these grains are eaten by humans or when they are fed to dairy cattle and they get into the milk supply, they affect humans. The synthesis of proteins on ribosomes that are different from those found in bacteria. This makes the fungi immune to those antimicrobial agents that are directed against the bacterial ribosome, e.g., chloramphenicol. The ability of certain metabolites to alter morphology of yeast and/or be assimilated by yeast with concomitant clinical identification affects.(6)
Ecology
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
The primary habitats for S. schenckii and Ceratocystis spp. are the soil and plants. In contrast to Ceratocystis, S. schenckii is not phytopathogenic. Preferential biological associations or even strict host specificities among these fungi have been recognized. For instance, C. ulmi is highly specific for elms. The ecology of S. schenckii determines the epidemiology of sporotrichosis. The conditions for the survival of S. schenckii in nature, such as temperature, humidity, and necessary nutrients, as well as the conditions favoring human infection, have been studied (106, 121). (4) S. schenckii is isolated most often from soil, live plants, or plant debris, wood, and straw, but it can also be found in insects, hair, water, air, and a variety of other sources (9, 16, 36, 163, 181). Several domestic animals and rodents are carriers of this fungus (95, 106, 127). Freitas et al. (43) described sporotrichosis in 12 dogs and 8 cats, but these animals were not regarded as natural reservoirs. Isolates from nature have different characteristics. Strains isolated by Mackinnon (106) from rotten palm tree trunks, dry grass from armnadillo and rodent holes or nests, and soil covered by mosses formned oval dark-pigmented radulaspores and numerous conidia. Multiple spicules were observed on the hyphae after conidial detachment. These strains grew at 370C and were pathogenic in mice. Strains isolated by Howard and Orr (67) from rat dung, wood, and soil did not grow at 370C, formed spherical, dark-pigmented conidia which could not be detached easily from hyphae, and were nonpathogenic. While tracing the source of contamination of a patient with sporotrichosis, Mariat (113) isolated an S. schenckii strain from Aechmea (Bromeliaceae), a decorative plant with thorny leaves, as well as from the soil around the plant. This plant had been maintained in a compost made with highly decayed manure or partially decayed beech and oak leaves or both. Particles of Sporothrix (300 particles per g) were recognized in the leaf litter but not in the manure. The strain isolated from the patient and the strain isolated from the plant were compared. Whereas the strain from the patient was in the yeast phase at 370C and was pathogenic for golden hamsters and mice, the presumed wild-type strain isolated from the soil around Aechmea grew faster at 30 than at 370C, converted only partially to the yeast phase, and was nonpathogenic in animals. A strain of S. schenckii isolated from the air in Paris (113) was also nonpathogenic in hamsters and mice. (4)
Ecology: Sporothrix schenckii is a cosmopolitan fungus, isolated from soil and decaying plant materials. Sphagnum moss and rose bushes are well known source of this organism. Laboratory Diagnosis: 1. Culture – Sporothrix schenckii is a thermal dimorphic fungus. At 25°C, on Sabouraud’s dextrose agar, colonies were initially white, becoming pinkish tan on the surface (Figure 7A) and reverse (Figure 7B). At 37°C, on enriched media like blood agar, brain heart infusion agar, colonies were cream to buff color, creamy in texture and grew in 2 weeks. 2. Microscopic morphology – Lactophenol cotton blue or Calcofluor mounts showed thin, hyaline septate hyphae; conidiophores were slender and tapering. At the end of conidiophores, ovoid, hyaline conidia were formed sympodially (rosette formation) (Figure 8). At 37°C, ovoid, single or multiple budding yeast cells were seen. 3. Differentiation from other molds – S. schenckii is differentiated from other fungi by its slow growth, initially white colonies turning black, and ovoid conidia produced sympodially (rosette formation). Nonpathogenic Sporothrix species do not convert to yeast phase at 37°C on enriched media. Ophiostoma stenoceras, a nonpathogenic fungus microscopically resembling Sporothrix, produces long necked perithecia after 2-3 weeks. Exophiala species produce annelloconidia, while Phialophora species produce phialoconidia, thus differentiating it from S. schenckii 4. In vitro susceptibility testing – Susceptibility testing results indicate that S. schenckii isolates are susceptible to amphotericin B, itraconazole, and ketoconazole, but less susceptible to fluconazole (3, 7). 5. Molecular tests –Karyotyping by pulse field gel electrophoresis (PFGE) of clinical isolates demonstrated 6-8 chromosomes and genome size of 28 Mbp (9). Mitrochondrial DNA analysis of Sporothrix schenckii for epidemiology purposes has been done (2).
Sporothrix schenckii. It is a thermally dimorphic fungus and the macroscopic morphology varies depending on the temperature of growth. At 25°C, colonies grow moderately rapidly. They are moist, leathery to velvety, and have a finely wrinkled surface. From the front and the reverse, the color is white initially and becomes cream to dark brown in time ("dirty candle-wax" color). At 37°C, colonies grow moderately rapidly. They are yeast-like and creamy. The color is cream to beige. The conversion of the mould form to the yeast form is required for definitive identification of Sporothrix schenckii [1295, 2144, 2202]. Sporothrix schenckii. Similar to its macroscopic morphology, microscopic features of Sporothrix schenckii also vary depending on the temperature of growth. At 25°C, septate hyaline hyphae, conidiophores, and conidia are observed. Conidiophores are sympodial and appear weakly differentiated from the vegetative hyphae. They often have an inflated base and arise at right angles from the hyphae. Conidia have two types. The first type are unicellular, hyaline to brown, oval, thin-walled, and are typically arranged in rosette-like clusters at the tips of the conidiophores. The second type of conidia are brown (dematiaceous),oval or triangular, thick-walled, cessile, and are attached directly to the sides of the hyphae. The latter type of conidia are typically present only in freshly isolated strains. At 37°C, Sporothrix schenckii produces oval to cigar-shaped (also called "cigar bodies") yeast cells. Single or multiple buds may be produced by a single yeast cell [1295, 2144, 2202].
Sporothrix schenckii var. luriei differs from Sporothrix schenckii by producing large, often septate, budding cells and by not assimilating creatine and creatinine
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Despite the existence of the fungus worldwide, infections due to Sporothrix schenckii are more common at certain geographical areas. Peru is an area of hyperendemicity for Sporothrix schenckii infectionsSporothrix schenckii is the causative agent of sporotrichosis ("rose handler's disease") [1909]. Sporotrichosis is a subcutaneous infection with a common chronic and a rare progressive course. The infection starts following entry of the infecting fungus through the skin via a minor trauma and may affect an otherwise healthy individual. Following entry, the infection may spread via the lymphatic route. Nodular lymphangitis may develop [1240, 2242]. Interestingly, an epidemic of sporotrichosis after sleeping in a rust-stained camping tent has been reported and the tent was identified as the source of infection [369]. Patients infected with Sporothrix schenckii may be misdiagnosed as pyoderma gangrenosum due to the large ulcerations observed during the course of sporotrichosis [354].
Pulmonary [672, 879, 1164] and osteoarticular infections [647, 1322], granulamatous tenosynovitis and carpal tunnel syndrome [2178], bursal infection [2374], endophthalmitis [1266, 2450], meningitis [698, 1752], invasive sinusitis [1574], and disseminated [1575, 2377] sporotrichosis have been described. The infection remains localized in immunocompetent individuals while fungemia and disseminated infection may be observed in immunocompromised patients, such as those with AIDS [39, 647, 856, 1266, 1354, 1574, 1752, 2377]. Fatal fungemia may develop also in patients with diabetes mellitus and alcoholism [398]. Primary (granulamatous) pneumonia without any cutaneous disease may develop in alcoholics [672]. Laboratory-acquired sporotrichosis has also been reported.
Fugomyces cyanescens is frequently considered to be nonpathogenic. It is avirulent in animal models and human cases in general do not suggest a clinical syndrome [2104]. However, pulmonary lesions and pneumonia due to Fugomyces cyanescens have been reported in organ transplant recipients
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
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References
(1) NCBI: Sporothrix schenckii, Accessed August 15, 2007, <http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=29908&lvl=3&lin=f&keep=1&srchmode=1&unlock>
(2) Doctor Fungus: Sporothrix Species, Accessed August 19, 2007, <http://www.doctorfungus.org/thefungi/Sporothrix.htm>
(3) Sindy Hu,1 Wen-Hung Chung,1 Shuen-Iu Hung,2 Hsin-Chun Ho,1 Zen-Whe Wang,1 Chien-Hsun Chen,1 Shu-Chuan Lu,3 Tseng-tong Kuo,3 and Hong-Shang Hong. "Detection of Sporothrix schenckii in Clinical Samples by a Nested PCR Assay". J Clin Microbiol. 2003
(4) Travassos LR, Lloyd KO. "Sporothrix schenckii and related species of Ceratocystis". Microbiol Rev. 1980 Dec;44(4):683-721.
(5) Lane JW, Grrison RG, Field MF. "Ultrastructural studies on the yeastlike and mycelial phases of Sporotrichum schenckii". J Bacteriol. 1969 Nov;100(2):1010-9
(6) The Fungi, Accessed August 23, 2007, <http://www.kcom.edu/faculty/chamberlain/Website/Lects/Fungi.htm#classif>
Edited by Whitney Johnson-Courtright of Rachel Larsen
