1. Eukaryotic Pathogens: Fungi

2. 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.

3. 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

4. Fungi
Table 12.1

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

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

7. 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

8. 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

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

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.

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

12. 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)

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

14. Lichens: Ascomycete with unicellular algae or cyanobacteria
Figure 12.10

15. 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.

16. 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

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

18. 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

19. 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

20. 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

21. 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.

22. 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.