taxonomic classification

1. Taxonomic Classification Characteristics of Ascomycota Reproduce sexually by ascospores – see 999 Reproduce asexually by conidia (common ?) May grow as yeast, molds (moulds), or dimorphic Mould forms have septate hyphae Reproduce sexually (ascospores) and asexually (various types of conidia)

3. Ascomycota Sexual Propagules 020. A linear, cylindrical, eight-spored ascus of Sordaria fimicola. Note ascosporogenesis (sexual reproduction in the Ascomycotina) involves the formation of ascospores, typically eight, by "free cell formation" within an ascus. 020. A linear, cylindrical, eight-spored ascus of Sordaria fimicola. Note ascosporogenesis (sexual reproduction in the Ascomycotina) involves the formation of ascospores, typically eight, by "free cell formation" within an ascus.

4. Two Types of Blastoconidia 080. Microscopic morphology of C. albicans showing budding spherical to ovoid blastoconidia.080. Microscopic morphology of C. albicans showing budding spherical to ovoid blastoconidia.

5. Taxonomic Classification Characterics of Basidiomycota Reproduce sexually by basidiospores Reproduce asexually by conidia with septate hyphae Basidiomycetes include rusts, smuts, mushrooms, and (rare) yeast One pathogenic basidiomycete is a yeast with a large capsule (e.g. anamorph is Cryptococcus neoformans with perfect form Filobasidiella neofomans,) Basidiomycetes are arguably the least important of the fungal classes as human pathogens

6. 015 015. Scanning electron micrograph showing a typical basidium of Agaricus campestris with four sterigmata and three remaining mature basidiospores. 015. Scanning electron micrograph showing a typical basidium of Agaricus campestris with four sterigmata and three remaining mature basidiospores.

7. Taxonomic Classification Characteristics of Deuteromycota Reproduce only asexually (anamorphs) Grow as yeast, moulds, and dimorphics Asexual propagules are conidia (singular conidium) Moulds of this group produce septate hyphae The majority of human pathogenic fungi are from the class Deuteromycota

8. Taxonomic Classification Characteristics of Deutermycota Some mycologists include Pneumocystis carinii in this group of fungi Mycoses include superficial, cutaneous, subcutaneous, and systemic Deuteromycetes may be opportunistic or classical pathogens

9. Clinical Classification - Intro All fungi are ubiquitous free-living environmental saprophytes, and appear to have no requirement to function as parasites = fungal infections and the diseases they cause are accidental. Compared to other human pathogens, little is known about fungal pathogenesis beyond mechanical damage caused by spreading hyphae. Pathology varies in many ways. It can be acute or chronic, clinically inapparent to obvious, can result in immune response that is slight – vigorous and transient to prolonged. Although we discuss clinical forms of mycoses as discrete they are not, and these categories do not really work. This is esp. true of cutaneous vs superficial mycoses – overlap.

10. Clinical Classification: systemic *obviously most severe, and least likely in persons that are immunocompetent *only 6 recognized species (see table 19-3) but the list may expand soon (others being considered) *most are 1’ respiratory &/or circulatory pathogens *highly virulent species, capable of spreading widely via host circulatory system (in macrophages, etc.). *most are dimorphic – systemic in yeast form – triggered via change in temperature & perhaps host immune avoidance *although rare, may cause cutaneous / subcutaneous infections without evidence of dissemination.