Chapter 12 Eukaryotic Microbs Flashcards Preview

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Flashcards in Chapter 12 Eukaryotic Microbs Deck (15):
1

Microscopic eukaryotes

Fungi
Algae
Protist
Multicellular organisms and arthropods

2

Fungi Classification

Chytridiomycetes
Ascomycetes
Basidiomycetes
Zygomycetes

3

Structure of Fungi

Most fungi multicellular; composed of hyphae
• Visible mass of hyphae is a mycelium

4

Fungal Habitats

• Grow in concentrations of salts, sugars, acids, alkalis that kill most bacteria,
• Most prefer 20°C to 35°C but easily survive lower temperatures; some grow below freezing
• Spoil pickles, fruit preserves, and refrigerated food
• Most aerobic; some yeasts facultative anaerobes
• Some obligate anaerobes live in rumen of cows

5

Fungi Symbiotic Relationships

• Lichens are association of fungus and photosynthesizer

• Mycorrhizas: beneficial association with plant roots

• Certain insects depend on fungi

6

Reproduction a fungus

Spore: reproductive cells formed sexually or asexually, carried by wind, water

• Reproduction results from fusion of hyphae from two different mating types

• Yeast may reproduce by mitosis or budding

7

Algae

▪ Simple photosynthetic eukaryotes: protists

• Differ from plants by lack of organized vascular system; simple reproductive structures

8

Medical Importance of Algae

• Do not directly cause human disease

• Indirectly via toxins

• Algal blooms from upwelling of nutrients and warmer temperatures, fertilizer runoff, untreated sewage

9

Protozoa

▪ Types of Protozoa

• Extreme diversity; some cause human diseases

• Apicomplexans: parasites with apical complex at one end; helps penetrate membrane of host cells

10

Medical Importance of Algae

▪️Majority do not cause disease, but protozoan pathogens have significant global health impact
• ~malaria each year; ~660,000 deaths
• Amebiasis
• Giardia among leading causes of diarrhea worldwide
• Trypanosomes (sleeping sickness) have made some regions of Africa uninhabitable for centuries

11

Multicellular Parasites: Helminths

▪ nematodes (roundworms),
▪ cestodes (tapeworms),
▪ trematodes (flukes)

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Roundworms (nematodes)

• Cylindrical, tapered body
• Digestive tract extends from mouth to anus

13

Tapeworms (cestodes)

• Flat, ribbon-shaped bodies; may exceed 1 m in length
• No digestive system; absorb nutrients through body
• Head end (scolex) attaches to intestines of host
• Segments (proglottids) contain male, female structures

14

Flukes (trematodes)

• Flat, leaf-shaped
• Suckers hold in place while sucking fluids from host
• Blood fluke most common cause of schistosomiasis, results in 20,000 deaths/year
• Females lay eggs in blood vessels near intestine
• Inflammatory reactions cause rupture of vessels; eggs released into intestines, excreted with feces

15

Arthropods

▪️insects and arachnids
• Serve as vectors of transmission
• Mechanical: transfer pathogen from one surface to another
• Biological: essential part of life cycle