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

2. Kingdom Fungi The Fungi
Aerobic (molds and yeasts) or facultatively anaerobic (yeasts)
Chemoheterotrophic
Most are decomposers
Mycology is the study of fungi
>100,000 species
~200 are pathogenic to humans/animals

3. Fungi vs. Bacteria
asexual

4. The Fungi: Molds Filamentous fungi (mostly aerobic)
Hyphae: cellular filaments
Vegetative hyphae: responsible for obtaining nutrients
Aerial hyphae: responsible for reproduction (often bear spores)
Mycelium: macroscopic mass of hyphae
Figure 12.2

5. The Fungi: Molds Reproduction Fragmentation of hyphae (asexual)
Production of spores (sexual or asexual)
Asexual spores: from hyphae of one organism; genetically identical to parent
Sexual spores: from fusion of two nuclei of opposite mating strains of the same species
Released spores will germinate to form a new mold
Spores may be important in identification of fungal species
Figure 12.1
Figure 12.5

6. The Fungi: Yeasts Nonfilamentous, unicellular, round/oval
Reproduce by budding or fission
Capable of facultative anaerobic growth
Absence of oxygen, ferment carbohydrates into alcohol and carbon dioxide
Figure 12.3

7. The Fungi: Dimorphism
Demonstrate both yeastlike and moldlike growth, depending on environmental conditions (temperature, CO2 levels, etc.)
Figure 24.17

8. The Fungi: Adaptations
Fungi have adapted to thrive where many bacteria can’t
Good growth at pH 5
Tolerant of high osmotic pressure
Growth in the presence of low moisture
Metabolize complex carbohydrates that most bacteria cannot
Molds are likely to spoil food that bacteria can’t

9. The Fungi: Infections (mycoses)
Mycoses are typically serious in immunocompromised individuals
Systemic mycoses Deep within body
Subcutaneous mycoses Beneath the skin
Cutaneous mycoses Affect hair, skin, nails
Opportunistic mycoses Caused by normal microbiota or fungi that are left unchecked

10. The Fungi: Infections (mycoses)
Candidiasis: Candida albicans (Cutaneous mycosis)
Constituent of normal microbiota of the genitourinary tract and mouth (relatively small population)
Infection frequently occurs in people treated with broad-spectrum antibacterial drugs
Thrush, vaginitis (yeast infections)
Figure 21.17

11. The Fungi: Infections (mycoses)
Pneumocystis pneumonia: most common life-threatening infection for AIDS patients
Pneumocystis jiroveci
Opportunistic fungus
Systemic mycosis; uncommon before AIDS epidemic
Considered to be an initial clue for AIDS

12. Kingdom Protista: The Protozoa
Unicellular eukaryotes
Found mostly in soil and water
Mostly aerobic
Chemoheterotrophs
Vegetative form is a trophozoite
Feeding/growing stage, typically motile
Digestion in vacuoles, waste eliminated through plasma membrane or an anal pore

13. Protozoa
Asexual reproduction by fission, budding, or schizogony (multiple fission)
Sexual reproduction by some
Live in areas with large supply of water
Some produce cysts in adverse conditions
Protective capsule
Survival in harsh conditions
Survival of parasitic species outside of host

14. Parasitic Protozoa: Role of Cysts
Trichomonas vaginalis
Parasite
No cyst stage
Figure 12.17b

15. Parasitic Protozoa: Role of Cysts
Giardiasis (prolonged diarrhea)
Giardia lamblia attaches firmly to human intestinal wall
~7% of humans are healthy carriers; shed cysts in feces
Most outbreaks due to contaminated water supplies
Diagnosis: presence of cysts in feces or the string test (to detect trophozoites in upper bowel)
Figure 12.17d
Figure 25.18

16. Protozoa: Mechanisms of Motility
Cilia
Flagella
Pseudopods
May also be used for food ingestion (phagocytosis)
Figure 12.18a

17. Parasitic Protozoa: Complex Life Cycles
Some species have complex life cycles
Multiple hosts
Plasmodium (causes malaria)

18. Plasmodium and Malaria
Malaria: mill people worldwide are infected each year
Two hosts:
Mosquito
Definitive host: harbors sexually reproducing stage
Human
Intermediate host: harbors asexually reproducing stage
Destruction of red blood cells (anemia)
Release of toxins (fever/chill cycles)
Alteration of RBC shape can clog tissue capillaries (kidney, liver, brain damage)
Figure 23.25

19. Parasitic Protozoa with Complex Life Cycles: Plasmodium1 2
Schizogony in liver cell; merozoites are produced
Sporozoites in salivary gland
Infected mosquito bites human; sporozoites migrate through bloodstream to liver of human 9
Resulting sporozoites migrate to salivary glands of mosquito 3
Merozoites released into bloodsteam may infect new red blood cells
Sexual reproduction
Asexual reproduction 8
In mosquito’s digestive tract, gametocytes unite to form zygote
Zygote
Intermediate host
Female gametocyte 4
Merozoite develops into ring stage in red blood cell
Male gametocyte
Ring
stage 5
Ring stage grows and divides, producing merozoites
Definitive host 7
Another mosquito bites infected human and ingests gametocytes 6
Merozoites are released when red blood cell ruptures; some infect new red blood cells, and some develop into male and female gametocytes
Merozoites
Figure 12.19

20. Kingdom Animalia: The Helminths
Platyhelminthes
(Flatworms)
Nematodes
(Roundworms)
Helminths (parasitic worms)
Multicellular animals
Chemoheterotrophic
Complex life cycles (often several hosts)
Intermediate and definitive hosts
Transmission usually by ingestion
Often produce few symptoms
Flukes
Tapeworms

21. The Helminths
Characteristics that distinguish parasitic helminths from other free-living animals:
May lack a digestive system (can absorb nutrients from host)
Reduced nervous system (don’t have to search for food or respond much)
Locomotion may be reduced or absent
Often complex reproductive system
Monoecious: hermaphroditic
Dioecious: separate sexes

22. The Helminths: Flukes Flat, leaf-shaped
Oral and ventral suckers hold fluke in place
Absorb food through cuticle
Figure 12.25

23. The Helminths: Lung Fluke life cycle
Diagnosis
Figure 12.26

24. The Helminths: Tapeworms
Intestinal parasites
Complete lack of digestive system
Scolex (head) includes suckers and hooks for attachment
Segmented
Proglottids: contain male and female reproductive organs
When mature, they are “bags of eggs”
Figure 12.27

25. The Helminths: Tapeworms
Beef tapeworm (Taenia saginata)
Cattle ingest proglottids
Larvae hatch, bore through intestinal wall and migrate to muscle (meat) and encyst (cysticerci)
Humans eat infected meat, and digest all parts except the scolex
Scolex latches on to intestinal wall and begins producing proglottids (can grow up to 6 meters!)
Vague abdominal discomfort
Diagnosis: presence of proglottids/eggs in feces

26. The Helminths: Roundworms
Cylindrical, tapered at the ends
Complete digestive system
Motile
Mostly dioecious
Figure 25.25
Figure 25.21

27. The Helminths: Roundworms
Ascariasis (Ascaris lumbricoides)
Acquired by ingestion of eggs
Eggs, excreted in feces, can survive in soil up to 10 yr
Larvae travel to lungs, where they grow
Adults up to 1 foot in length, inhabit small intestine
Diagnosis: presence of eggs in feces