1. The Eukaryotes: Fungi, Algae, Protozoa, and Helminths Part 1
Chapter 12
The Eukaryotes: Fungi, Algae, Protozoa, and Helminths
Part 1

2. Fungi, Algae, Protozoa, and Helminths

3. Fungi Mycology: the study of fungi
rRNA sequencing causing many reclassification
Eukaryotic (unicellular, filamentious, fleshy)
Aerobic or facultatively anaerobic
Chemoheterotrophic
Most are decomposers (important in the food chain); absorb nutrients instead of ingestion
decompose dead plant matter (organic molecules to inorganic molecules) & recycle vital elements

4. Fungi Few are plant and human pathogens
Incidence of serious fungal infections have been rising
Nosocomial infections and in people who are immunocompromised
Beneficial
Recycling of nutrients in the environment
Symbiotic fungi (mycorrhizae) help plants roots absorb minerals and water from the soil
Serve as food; used to produce foods and drugs for humans

5. Fungi
Table 12.2

6. Characteristics of Fungi
Fungal structures are used for identification in a clinical laboratory
Yeast identification based on biochemical tests
Multicellular fungi based on physical appearance: 1) colony characteristics, 2) type of hyphae, and 3) reproductive spores (asexual spores for clinical ID & sexual spores for phyla)
Fungal colonies (vegetative structures) are composed of the cells involved in catabolism and growth

7. Molds and fleshy fungi
The fungal thallus (body) consists of hyphae; a mass of hyphae is a mycelium.
Hypha (pl. hyphae): a long filament of cells in fungi
Septate hyphae: hyphae with cross-walls (septa)
Coenocytic hyphae: hyphae with no septa
Fig. 12.1

8. Molds and fleshy fungi
Vegetative hypha: the portion of a hypha that obtains nutrients
Reproductive (aerial) hypha: the portion of a hypha concerned with reproduction
Aerial hyphae bear reproductive spores
Figure 12.2

9. Yeasts
Unicellular fungi; usually spherical or oval shape; usually reproduce by budding
Capable of facultative anaerobic growth
Fermentation used in brewing, wine-making, and baking
Pseudohypha: A short chain of fungal cells that results from the lack of separation of daughter cells after budding
Yeast cells grown on a solid medium resemble bacterial colonies

10. Yeasts Fission yeasts divide symmetrically (e.g. Saccharomyces)
Budding yeasts divide asymmetrically
Figure 12.3

11. Dimorphic fungi
Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C
Moldlike form produce aerial and vegetative hyphae
Yeastlike form reproduce by budding
Figure 12.4

12. Life cycle
Filamentous fungi can reproduce asexually by fragmentation of their hyphae
Sexual and asexual reproduction through formation of spores (formed from aerial hyphae)
Fig. 12.1

13. Life cycle
Asexual spores: formed by the hyphae of one organism through mitosis
Gives rise to a new mold that is genetically identical to the parent
Sexual spores: result from the fusion of nuclei from 2 opposite mating strains of the same species of fungus
Gives rise to a new mold that has genetic characteristics of both parental strains
Usually produced in response to changes in environment

14. Asexual spores Sporangiosphore Chlamydospore
form within a sac called sporangium at the end of a sporangiophore (aerial hypha), e.g. Rhizopus
Chlamydospore
a thick-walled spore formed by rounding and enlargement within a hyphal segment e.g. Candina albicans (yeast)
Figure 12.5

15. Asexual spores Conidiospore (conidium)
a unicellular or multicellular spore that is not enclosed in a sac; produced in a chain at the end of a conidiophore (aerial hypha), e.g. Aspergillus
Arthrospore: formed by the fragmentation of a septate hypha into single, slightly thickened cells, e.g. Coccidioides immitis
Blastoconidium: buds coming off the parent cell, e.g. C. albicans (yeast) and Cryptotoccus

16. Conidiospores
Figure 12.5

17. Sexual spores Results from sexual reproduction Three phases
Plasmogamy Haploid donor cell nucleus (+) penetrates cytoplasm of recipient cell (–)
Karyogamy + and – nuclei fuse
Meiosis Diploid nucleus produces haploid nuclei (sexual spores)
In laboratory setting, most fungi exhibit only asexual spores (used for clinical identification)

18. Sexual spores
Zygospore Fusion of haploid cells produces one zygospore e.g. Rhizopus
Figure 12.6

19. Sexual spores Ascospore Formed in a sac (ascus), e.g. Penicillium
Figure 12.7

20. Sexual spores
Basidiospore Formed externally on a pedestal (basidium), e.g. mushrooms
Figure 12.8

21. Nutritional adaptations
Fungi adapted to environments that would be hostile to bacteria
Usually grow better in acidic environment (pH of about 5) & require less nitrogen for growth
Aerobic (molds) or facultative anaerobes (yeasts)
More resistant to osmotic pressure (can grow in relatively high sugar or salt concentration)
Can grow on a very low moisture surface
Capable of metabolizing complex carbohydrates (e.g. lignin)

22. Medically Important Phyla of Fungi
Not all fungi cause disease
many are found as contaminants in foods and in as contaminants on bacterial cultures (laboratory)
Four phyla: Zygomycota, Ascomycota, & Basidiomycota (these are telomorphs); and Anamorphs (Deuteromycota)
Telomorphs: produce both sexual and asexual spores; the sexual stage in the life cycle of a fungus
anamorphs: Ascomycete fungi that have lost the ability to reproduce sexually; the asexual stage of a fungus (asexual spores only)

23. Medically Important Phyla of Fungi
Zygomycota (conjugation fungi)
Saprophytic (obtain nutrients from dead organic matter) molds with coenocytic hyphae
Asexual spore = sporangiospores; sexual spores = zygospores
e.g. Rhizopus & Mucor (Opportunistic, systemic mycoses) Rhizopus nigricans (common bread mold)

24. Zygomycete Life Cycle
Figure 12.6

25. Medically Important Phyla of Fungi
Ascomycota (sac fungi)
molds with septate hyphae and some yeasts
Sexual spores = ascospore; and frequently asexual spores = conidiospores
e.g. Aspergillus (opportunistic, systemic mycosis) Blastomyces dermatitidis, Histoplasma capsulatum (systemic mycoses) Microsporum, Trichophyton (cutaneous mycoses)

26. Ascomycete Life Cycle
Figure 12.7

27. Medically Important Phyla of Fungi
Basidiomycota (club fungi, mushrooms)
Molds with septate hyphae
Sexual spores = basidiospores; and sometimes asexual spores = conidiospores
Cryptococcus neoformans (systematic mycosis)

28. Basidiomycete Life Cycle
Figure 12.8

29. Anamorphs Anamorphic fungi:
Produce asexual spores only; historically fungi whose sexual cycle had not been observed were called Deuteromycota
rRNA sequencing places most in Ascomycota, a few are Basidiomycota
e.g. Penicillium Sporothrix (subcutaneous mycosis) Stachybotrys, Coccidioides, Pneumocystis (systemic mycoses) Candida albicans (Cutaneous mycoses)

30. Fungal Diseases (mycoses)
Tend to be chronic (long-lasting) infections due to slow growth of fungi & hard to treat
Drugs that will affect fungal cells (eukaryotes) also affect animal cells (also eukaryotes)
Systemic mycoses: deep within body
Usually caused by fungi living in soil
Subcutaneous mycoses: beneath the skin
Usually caused by saprophytic fungi living in soil and on vegetation

31. Cutaneous mycoses: affect hair, skin, nails
Usually caused by fungi living in soil, on animals or humans (can be transmitted from human to human or from animal to human)
Superficial mycoses: localized, e.g., hair shafts, and surface epidermal cells
Prevalent in tropical climates

32. Fungal Diseases (mycoses)
Opportunistic mycoses: caused by normal microbiota or fungi that are normally harmless
infect immunocompromised host; patients on broad-spectrum antibiotics; or people who is seriously debilitated or traumatized

33. Economic Effects of Fungi
Used in biotechnology, biological pest controls vs. undesirable effects
Gypsy moth control
Entomorphaga
Ceratocystis ulm (Dutch elm disease)
Taxol production
Taxomyces
Cryphonectria parasitica (chestnut blight)
Cellulose used for juices and fabric
Trichoderma
Food spoilage
Negative Effects
Bread, wine, beer
Saccharomyces
Positive Effects
Fungi

34. Lichens
Mutualistic combination of an alga (or cyanobacterium) & fungus
Classified according to the fungal partner (most often an ascomycete)
Mutualism: a type of symbiosis in which both organisms or populations are benefited
Alga produces and secretes carbohydrates (via photosynthesis), fungus provides holdfast (enclose alga)
Some of the slowest growing organisms on Earth

35. Lichens
Figure 12.10

36. Lichens
Often the first life forms to colonize newly exposed soil or rock
Colonize habitats that are unsuitable for either the alga or the fungus alone
Grouped into 3 morphologic categories
Crustose, foliose, and fruiticose
Used as dyes for clothing, an antimicrobial agent, the dye in litmus paper; cause allergic contact dermatitis