fungi, algae, protozoa, and helminths - las positas...

Copyright © 2010 Pearson Education, Inc.

Ch 12

The Eukaryotes:

Fungi, Algae,

Protozoa, and

Helminths


Student Learning Outcomes

List the defining characteristics of fungi.

Identify two beneficial and two harmful effects of fungi.

List the defining characteristics of protozoa.

Differentiate an intermediate host from a definitive host.

List the distinguishing characteristics of the two classes of parasitic helminths, and give an example of each.

Provide a rationale for the elaborate life cycles of parasitic worms.

Define arthropod vector.

Differentiate between a tick and a mosquito, and name a disease transmitted by each.


FUNGI Chemoheterotroph, aerobic

(molds) or facultativelyanaerobic (yeasts)

Mycology: Study of fungi

Most fungi decomposers, few are parasites of plants and animals.

# of serious fungal infections increasing

Review Table 12.2

Fig. 12.1


Hyphae: Filaments of cells, mostly septate

Mycelium: Mass of hyphae.

Molds: mostly filamentous.

Yeasts: nonfilamentous, unicellular fungi.

Budding yeasts divide asymmetrically.

Dimorphic fungi: yeasts like 37C, molds 25C.

Fungal spores differ from bacterial spores. Form from aerial hyphae.

Growth in acidic, low-moisture, high osmotic pressure environments.

Metabolize complex carbohydrates (e.g.: lignin).

Characteristics of Fungi


Economic Effects of Fungi

Saccharomyces cerevisiae: Bread, wine, HBV

vaccine

Trichoderma: Cellulase

Taxomyces: Taxol

Entomophaga: Biocontrol

Paecilomyces: Kills termites

Mold spoilage


Fungal Diseases – Mycoses

1. Systemic mycosis: infection deep within body, affects many tissues and organs. Histoplasmosis and coccidiomycosis.

2. Subcutaneous mycosis: Saprophytic fungi, e.g.: Sporotrichosis.

3. Cutaneous mycosis = Dermatomycosis: affects keratin-containing tissues (hair, nails, skin).

4. Superficial mycosis: localized on hair shafts and superficial skin cells.

Opportunistic mycoses:

caused by normal microbiota or fungi that are not usually pathogenic (E.g.: Candidiasis and Pneumocystis pneumonia)

usually systemic.


Human eyelash

with unknown

fungus infection.

Minimal damage to

skin or underlying

tissues.

However, impaired

IS can encourage

the infecting fungus

to proliferate.


ALGAEMostly photoautotrophs,

mostly in ocean

Diatoms

Unicellular, store

energy in form of oil

Domoic acid Neurological disease

Ingestion of mussels that fed on diatomes (also

affects birds and sealions)

Dinoflagellates (plankton)

Some produce neurotoxins: red tide

Kills fish, marine mammals, and humans, e.g.:

parasitic shellfish poisoning (PSP)


PROTOZOA

Unicellular, eukaryotic chemoheterotrophs. Large and diverse group. Few are pathogenic.

Found in soil and water and as normal microbiota in animals.

Trophozoite: Vegetative form (feeding and growing).

Asexual reproduction via fission, budding, or schizogony (multiple fission).

Sexual reproduction via conjugation.

Some protozoa can produce a cyst that provides protection during adverse environmental conditions.


Medically Important Protozoa

1. Arcaezoa (lack mitochondria) Trichomonas and Giardia

2. Microspora (no mitochondria and no microtubules) – diarrhea and keratoconjunctivitis in AIDS patients

3. Amoebozoa (move via pseudopodia) Entamoeba (dysentery) and Acanthamoeba

4. Apicomplexa: not mobile, intracellular

Plasmodium, Babesia, Toxoplasma, Cryptosporidium

5. Euglenozoa: Hemoflagellates Trypanosoma


Amoebozoa

Move by

pseudopods

Entamoeba

Acanthamoeba

2

3

67

8

Fig 12.18

The Life Cycle of Plasmodium vivax


Fig 23..22

Euglenozoa

Move by flagella

Hemoflagellates

Trypanosoma spp.

Sleeping

sickness

Chagas’

disease


HELMINTHS (Parasitic Worm)

Kingdom: Animalia

Phylum: Platyhelminthes

(flatworms)

Class: Trematodes (flukes)

Class: Cestodes (tapeworms)

Phylum: Nematoda (roundworms)

few are human parasites

Anatomy and life cycle modified for parasitism

Adult stage in definitive host.

Each larval stage in specific intermediate host.


Life Cycle of Helminths

Monoecious (hermaphroditic)

Male and female reproductive systems in one animal

Dioecious

Separate male and female

Egg larva(e) adult

Platyhelminths

Dorsoventrally flattened

Trematode, or fluke: Oral and ventral sucker attaches to host tissue

Cestode, or tapeworm: Scolex (head), proglottids

4 suckers and

rostellum with hooks

Gravid proglottid with

uterine branches

Fig 12.26


Taenia solium

Taenia saginata

Human definitive host;

pig or cattle intermediate host.

Echinococcus granulosus

Fig. 12. 27

Human as

Definitive Host Taenia saginataCysticerci in beef

muscle

Intermediate HostEchinococcus

granulosusAdult in dog

Human is ….


Nematodes

Roundworms have a complete digestive system

.

Eggs infective for humans:

Ascaris lumbricoides: Ascariasis. 2nd most common worm infection in US. (Most common worldwide; > 1 bio infected)

Enterobius vermicularis (pinworm). Most common worm infection in US (30% of children, 16% of adults infected)


Fig12.28

Pinworm / Enterobius vermicularis

Diagnosing Pinworm Disease

Do test immediately

after waking up.

Several samples

might need to be

examined.

Since scratching of

the anal area is

common, samples

taken from under the

fingernails may also

contain eggs.

pinworm paddle


Larvae Infective for HumansFig 25.23

Hookworms

Ancylostoma duodenale and

Necator americanus

Trichinellosis:

The Life Cycle of Trichinella spiralis


Primarily in dogs and cats human heart failure,

also in human lungs

Spread via mosquitoes

Fig 12.29

The Heartworm Dirofilaria immitis


ARTHROPODS AS VECTORS

Kingdom: Animalia

Phylum: Arthropoda (exoskeleton, jointed legs, segmented body)

Class: Insecta (6 legs)

Lice, fleas, mosquitoes

Class: Arachnida (8 legs)

Mites and ticks

Arthropods that carry diseases are called vectors.

Elimination of vectorbornediseases best via control or eradication of vectors.


Arthropod Vectors

Mechanical transmission

Biological transmission

Microbe multiplies in vector

Definitive host

Microbe’s sexual reproduction in vectorFig 12.32

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