Eukaryotic Pathogens: Fungi

Eukaryotic Pathogens: Fungi What types of eukaryotic organisms are pathogenic, and how do they differ from bacteria? Fungi Classification Hyphae and multicellularity Cell walls: sepatate or coenocytic hyphae Spores: sexual or asexual Unicellular Yeasts Three-Four Major Medically Impt. Groups Zygomycetes: Conjugation Molds Ascomyctes: Sac Fungi Basidomycetes: Club Fungi Fungal Diseases: Mycoses Aspergillosis, histoplasmosis, candidiasis, etc Better Adaptation to Hostile Environments Eukaryotic pathogens are mostly parasitic and are difficult to target selectively with drugs since their cells are so similar to human cells.

The Fungi Eukaryotic Aerobic or facultatively anaerobic Chemoheterotrophic Most are decomposers Mildly acidophilic, acid tolerant More osmotically tolerant than bacteria Mycology is the study of fungi

Fungi Table 12.1

Molds Molds consist of hyphae; a mass of hyphae is a mycelium. 1 hypha Figure 12.2

Key Characteristics: Cell Walls, Spore Types (Aseptate) Sometimes hyphal cells are dikaryotic

Types of Spores: Asexual or Sexual Zygomycota Zygomycota Ascomycota Basidiomycota Ascomycota, Basidiomycota Conidiospores (asex.) Ascospores (sexual) Basidospores (sexual) Zygospores (sexual) Sporangiospores (asex.) Sexual spores arise from meiosis Asexual spores arise from mitosis

Yeasts : Single-celled Fungi Unicellular fungi, ovid Fission yeasts divide symmetrically Budding yeasts divide asymmetrically Mycoses: Candidiasis (local and systemic) from Candida albicans Beneficial: Saccharomyces cerevesiae/baker’s yeast Figure 12.3

Dimorphism Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C Figure 12.4

Eukaryotic Pathogens: Fungi What types of eukaryotic organisms are pathogenic, and how do they differ from bacteria? Fungi Classification Hyphae and multicellularity Cell walls: sepatate or coenocytic hyphae Spores: sexual or asexual Unicellular Yeasts Three-Four Major Medically Impt. Groups Zygomycetes: Conjugation Molds Ascomyctes: Sac Fungi Basidomycetes: Club Fungi Fungal Diseases: Mycoses Aspergillosis, histoplasmosis, candidiasis, etc Better Adaptation to Hostile Environments Eukaryotic pathogens are mostly parasitic and are difficult to target selectively with drugs since their cells are so similar to human cells.

Zygomycete Life Cycle: Conjugation Molds Coenocytic hyphae. Produces sporangiospores and zygospores E.g. Rhizopus/black bread mold Figure 12.6

Ascomycete Life Cycle: The Sac Fungi Septate hyphae. Produces ascospores or conidiospores Systemic mycoses: Aspergillosis , histoplasmosis, penicilliasis Cutaneous mycoses: Microsporum/Trichophyton (jock itch, athlete’s foot, ringworm)

Basidiomycete Life Cycle: Club Fungi Septate hyphae. Produces basidiospores and sometimes conidiospores. Cryptococcus neoformans (systematic mycosis) Toxic Mushrooms (Amanita) Figure 12.8

Lichens: Ascomycete with unicellular algae or cyanobacteria Figure 12.10

Eukaryotic Pathogens: Fungi What types of eukaryotic organisms are pathogenic, and how do they differ from bacteria? Fungi Classification Hyphae and multicellularity Cell walls: sepatate or coenocytic hyphae Spores: sexual or asexual Unicellular Yeasts Three-Four Major Medically Impt. Groups Zygomycetes: Conjugation Molds Ascomyctes: Sac Fungi Basidomycetes: Club Fungi Fungal Diseases: Mycoses Aspergillosis, histoplasmosis, candidiasis, etc Better Adaptation to Hostile Environments Eukaryotic pathogens are mostly parasitic and are difficult to target selectively with drugs since their cells are so similar to human cells.

Aspergillosis (Aspergillus mold) respiratory or systemic Ascomycete Most commonly seen in immunocompromised patients May start in lungs as fungus ball or in sinuses Can become systemic (esp. in AIDS); endocarditis (valves) Bronchiectasis (scarring of bronchioles) Prefers aerobic environment Asthmatics may be allergic to mold spores Found in dead and decomposing plant material in nature Treated with amphotericin B; allergics with prednisone

Candidiasis caused by Candida albicans yeast Ascomycete Vaginitis (“vaginal yeast infection”) Systemic candidiasis, often in AIDS patients Treated with antifungals like nystatin Thrush

Histoplasmosis (Histoplasma capsulatum) Ascomycete Dimorphic: both yeast-like and mold-like Mild respiratory infection Acquired from airborne spores often in bird and bat feces Mostly immunocompromised patients; AIDS Often not treated, otherwise with amphotericin B

Pneumocystis pneumonia (Pneumocystis jurovecii) Yeast-like and protozoan-like Hard to culture and classify Pathogenic in immunosuppressed individuals (e.g. AIDS) Forms cysts in the lungs that rupture to release more cells Causes pneumonia Human-based organism only In its own group: Deuteromycota

Skin mycoses Usually caused by Trichophyton, Microsporum, or Epidermophyton Tinea corporis or capitis (ringworm) Tinea cruris (jock itch) Tinea pedis (athlete’s foot) All are ascomycetes Microsporum Epidermophyton

Eukaryotic Pathogens: Fungi What types of eukaryotic organisms are pathogenic, and how do they differ from bacteria? Fungi Classification Hyphae and multicellularity Cell walls: sepatate or coenocytic hyphae Spores: sexual or asexual Unicellular Yeasts Three-Four Major Medically Impt. Groups Zygomycetes: Conjugation Molds Ascomyctes: Sac Fungi Basidomycetes: Club Fungi Fungal Diseases: Mycoses Aspergillosis, histoplasmosis, candidiasis, etc Better Adaptation to Hostile Environments Eukaryotic pathogens are mostly parasitic and are difficult to target selectively with drugs since their cells are so similar to human cells.

Fungi vs Bacteria (Mycosterols) , genatmycin Sugar or salt tolerance More tolerant of high osmotic environments Less tolerant of high osmotic envir. (grows more easily on jams and jellies) Acid tolerance More tolerant of acidic environments Less tolerant of acidic environments (can culture on Sabourad agar) Moisture tolerance Tolerant of low moisture environments Requiring higher moisture environments (can grow on shoe leather!) Nitrogen requirements Require less nitrogen Require more nitrogen Carbohydrate produce Produces indigestible carbohydrates Most carbohydrates produced are digestible Can digest plant carbohydrates Can’t digest some plant carbos.