chapter 12faculty.mtsac.edu/cbriggs/12_lecture_presentation.pdf · (opportunistic, systemic...

Chapter 12

The Eukaryotes: Fungi, Algae, Protozoa, and

Helminths

12-1 List the defining characteristics of fungi. 12-2 Differentiate asexual from sexual reproduction,

and describe each of these processes in fungi. 12-3 List the defining characteristics of the four phyla

of fungi described in this chapter. 12-4 Identify two beneficial and two harmful effects of

fungi.

Learning Objectives

Kingdom Fungi

Nutritional Type Chemoheterotroph

Multicellularity All, except yeasts

Cellular Arrangement Unicellular, filamentous, fleshy

Food Acquisition Method Absorptive

Characteristic Features Sexual and asexual spores

Mycology: the study of fungi

Table 12.1 Selected Features of Fungi and Bacteria Compared.

Vegetative Growth

Molds The fungal thallus consists of hyphae; a mass of hyphae

is a mycelium Unicellular fungi Fission yeasts divide symmetrically Budding yeasts divide asymmetrically

Dimorphism Pathogenic dimorphic fungi are yeastlike at 37°C

and moldlike at 25°C

Figure 12.2 Characteristics of fungal hyphae.

Septum

Cell wall

Pore Nuclei

Septate hypha Coenocytic hypha Growth of a hypha from a spore

Figure 12.3a Aerial and vegetative hyphae.

Aerial hyphae

Aspergillus niger

Figure 12.4 A budding yeast.

Parent cell

Bud scar

Figure 12.5 Fungal dimorphism.

Yeastlike growth Moldlike growth

Figure 12.6a Representative asexual spores.

Conidia

Conidiophore

Figure 12.6b Representative asexual spores.

Arthrospores

Figure 12.6c Representative asexual spores.

Pseudohypha

Blastoconidia

Figure 12.6d Representative asexual spores.

Chlamydoconidium

Figure 12.6e Representative asexual spores.

Sporangiospores

Sporangiophore

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)

Sexual Spores

Zygospore: fusion of haploid cells produces one zygospore

Ascospore: formed in a sac (ascus) Basidiospore: formed externally on a pedestal

(basidium)

Medically Important Phyla of Fungi

Zygomycota Microsporidia Ascomycota Anamorphs

Basidiomycota

Zygomycota

Conjugation fungi Coenocytic Produce sporangiospores and zygospores Rhizopus, Mucor (opportunistic, systemic mycoses)

Figure 12.7 The life cycle of Rhizopus, a zygomycete.

Sporangiospore

Spore germinates to produce hyphae.

Vegetative mycelium grows. Sporangium

Sporangiophore

Sporangium bursts to release spores.

Aerial hypha produces a sporangium.

Gametes form at tip of hypha.

Sporangiospores

Spore germinates to produce hyphae.

Spores are released from sporangium.

Zygote produces a sporangium.

Karyogamy and meiosis.

Zygosporangium containing zygospore

Zygospore forms.

Plasmogamy.

Sexual reproduction

Asexual reproduction

Microsporidia

No hyphae No mitochondria Intracellular parasites Encephalitozoon intestinalis

Figure 12.8 The life cycle of Encephalitozoon, a microsporidian.

Cytoplasm breaks up around nuclei to form spores.

Cytoplasm grows, and nuclei reproduce.

New spores are released.

Spores are ingested or inhaled.

Vacuole Mature spores

Cytoplasm and nucleus enter.

Host cell

Spore injects tube into host cell.

Ascomycota

Sac fungi Septate Teleomorphic fungi Produce sexual and asexual spores

Ascospores and frequently conidiospores Aspergillus (opportunistic, systemic mycosis) Blastomyces dermatitidis, Histoplasma capsulatum

(systemic mycoses) Microsporum, Trichophyton (cutaneous mycoses)

Figure 12.9 The life cycle of Talaromyces, an ascomycete.

Vegetative mycelium grows.

Sexual reproduction Asexual

reproduction

Conidium germinates to produce hyphae.

Ascospore germinates to produce hyphae.

Conidia are released from conidiophore.

Hypha produces conidiophore.

Conidia

Conidiophore

Ascus opens to release ascospores.

Meiosis then mitosis.

Karyogamy.

Plasmogamy.

Ascospore

Anamorphs

Produce asexual spores only rRNA sequencing places most in Ascomycota; a few are

Basidiomycota Penicillium Sporothrix (subcutaneous mycosis) Stachybotrys, Coccidioides, Pneumocystis (systemic

mycoses) Candida albicans (cutaneous mycoses)

Basidiomycota

Club fungi Septate Produce basidiospores and sometimes

conidiospores Cryptococcus neoformans (systemic mycosis)

Figure 12.10 A generalized life cycle of a basidiomycete.

Sexual reproduction

Basidiospore germinates to produce hyphae.

Plasmogamy.

Vegetative Mycelium grows.

Fruiting structure (“mushroom”) develops.

Basidiospores are formed by meiosis.

Basidiospores mature.

Basidiospores are discharged.

Fragment grows to produce new mycelium.

Hyphal fragment breaks off vegetative mycelium.

Economic Effects of Fungi

Saccharomyces cerevisiae: bread, wine, HBV vaccine

Trichoderma: cellulase Taxomyces: taxol Entomophaga: biocontrol Coniothyrium minitans: kills fungi Paecilomyces: kills termites

Fungal Diseases (Mycoses)

Systemic mycoses: deep within body Subcutaneous mycoses: beneath the skin Cutaneous mycoses: affect hair, skin, and nails Superficial mycoses: localized, e.g., hair shafts Opportunistic mycoses: caused by normal

microbiota or environmental fungi

Check Your Understanding Assume you isolated a single-celled organism that

has a cell wall. How would you determine that it is a fungus and not a bacterium? 12-1

Contrast the mechanism of conidiospore and ascospore formation. 12-2

List the asexual and sexual spores made by Zygomycetes, Ascomycetes, and Basidiomycetes. 12-3

Why are microsporidia classified as fungi? 12-4 Are yeasts beneficial or harmful? 12-4

Lichens

12-5 List the distinguishing characteristics of lichens, and describe their nutritional needs.

12-6 Describe the roles of the fungus and the alga in a lichen.

Learning Objectives

Lichens

Mutualistic combination of an alga (or cyanobacterium) and fungus

Alga produces and secretes carbohydrates; fungus provides holdfast

Figure 12.11a Lichens.

Three types of lichens

Fruticose

Foliose

Crustose

Figure 12.11b Lichens.

Lichen thallus

Fungus Alga

Cortex

Algal layer

Fungal hyphae

Cortex

Rhizine

Medulla

Economic Effects of Lichens

Dyes Antimicrobial (Usnea) Litmus

Check Your Understanding What is the role of lichens in nature? 12-5 What is the role of the fungus in a lichen? 12-6

12-7 List the defining characteristics of algae. 12-8 List the outstanding characteristics of the five

phyla of algae discussed in this chapter. 12-9 Identify two beneficial and two harmful effects of

algae.

Learning Objectives

Kingdom Protista

Nutritional Type Photoautotroph

Multicellularity Some

Cellular Arrangement Unicellular, colonial, filamentous, tissues

Food Acquisition Method Diffusion

Characteristic Features Pigments

Figure 12.12a Algae and their habitats.

Red 𝛌𝛌

Orange 𝛌𝛌

Yellow 𝛌𝛌

Violet 𝛌𝛌

Blue 𝛌𝛌 Red algae

Multicellular green algae

Brown algae

Unicellular green algae, diatoms, dinoflagellates

Sublittoral zone

Littoral zone

Green algae, cyanobacteria, euglenoids

LAND SURFACE

Algal habitats

Figure 12.12 Algae and their habitats.

Pneumatocyst Blade

Brown alga (Macrocystis)

Red alga (Microcladia)

Figure 12.13a Green algae.

Multicellular green alga (Ulva)

Figure 12.14a Diatoms.

Eunotia, a freshwater diatom that grows in acidic water

Figure 12.15 Peridinium, a dinoflagellate.

Flagellum

Produce male and female hyphae.

Figure 12.16 Oomycotes.

Sexual reproduction

Male antheridial hyphae grow around female oogonium and insert their nuclei into the oogonium.

Zygotes are released.

Zygote germinates.

Vegetative hyphae grow on organic matter.

Hyphae produce sporangia.

On a suitable substrate, zoospore germinates to produce hyphae.

Motile zoospores swim from the sporangium.

Zoospore

Oogonium

Antheridial hypha

Phaeophyta

Brown algae (kelp) Cellulose and alginic acid cell walls Multicellular Chlorophyll a and c, xanthophylls Store carbohydrates Harvested for algin

Rhodophyta

Red algae Cellulose cell walls Most are multicellular Chlorophyll a and d, phycobiliproteins Store glucose polymer Harvested for agar and carrageenan

Chlorophyta

Green algae Cellulose cell walls Unicellular or multicellular Chlorophyll a and b Store glucose polymer Gave rise to plants

Figure 12.13b Green algae.

Life cycle of a unicellular green alga (Chlamydomonas)

Zygote formation

Fertilization

Meiosis

Growth

Nucleus

Chloroplast

Gamete formation

Cell wall

Stored starch

Eyespot

Flagella

Mitosis

Sexual reproduction

Growth

Diatoms

Pectin and silica cell walls Unicellular Chlorophyll a and c, carotene, xanthophylls Store oil Fossilized diatoms formed oil Produce domoic acid

Figure 12.14 Diatoms.

Asexual reproduction of a diatom

Eunotia, a freshwater diatom that grows in acidic water

Dinoflagellates

Cellulose in plasma membrane Unicellular Chlorophyll a and c, carotene, xanthins Store starch Some are symbionts in marine animals Neurotoxins cause paralytic shellfish poisoning

Flagellum

Oomycota

Cellulose cell walls Multicellular Chemoheterotrophic Produce zoospores Decomposers and plant parasites Phytophthora infestans responsible for Irish potato blight P. cinnamoni infects Eucalyptus P. ramorum causes “sudden oak death”

Water molds

Produce male and female hyphae.

Figure 12.16 Oomycotes.

Sexual reproduction

Male antheridial hyphae grow around female oogonium and insert their nuclei into the oogonium.

Zygotes are released.

Zygote germinates.

Vegetative hyphae grow on organic matter.

Hyphae produce sporangia.

On a suitable substrate, zoospore germinates to produce hyphae.

Motile zoospores swim from the sporangium.

Zoospore

Oogonium

Antheridial hypha

Check Your Understanding How do algae differ from bacteria? From fungi?

12-7 List the cell wall composition and diseases caused

by the following algae: diatoms, dinoflagellates, oomycotes. 12-8, 12-9

Protozoa

12-10 List the defining characteristics of protozoa. 12-11 Describe the outstanding characteristics of the

seven phyla of protozoa discussed in this chapter, and give an example of each.

12-12 Differentiate an intermediate host from a definitive host.

Learning Objectives

Kingdom Various

Multicellularity None

Cellular Arrangement Unicellular

Food Acquisition Method Absorptive; ingestive

Characteristic Features Motility; some form cysts

Protozoa

Characteristics of Protozoa

Vegetative form is a trophozoite Asexual reproduction is by fission, budding, or

schizogony Sexual reproduction by conjugation Some produce cysts

Medically Important Phyla of Protozoa

Diplomonads Parabasalids Euglenozoa Amebae Apicomplexa Dinoflagellates Ciliates

Diplomonads

No mitochondria Multiple flagella Giardia lamblia

Figure 12.18 Members of the super kingdom Excavata.

Giardia trophozoites. Giardia cyst.

Parabasalids

No mitochondria Multiple flagella No cyst Trichomonas vaginalis

Figure 12.18d Members of the super kingdom Excavata.

Trichomonas vaginalis.

Axostyle Undulating membrane

Flagella

Euglenozoa

Move by flagella Euglenoids Photoautotrophs

Hemoflagellates Trypanosoma spp.

− Sleeping sickness −Chagas’ disease

Figure 12.18e Members of the super kingdom Excavata.

Euglena.

Chloroplasts

Eye spot

Flagella

Figure 23.23 Trypanosoma cruzi, the cause of Chagas’ disease (American trypanosomiasis).

Amebae

Move by pseudopods Entamoeba Acanthamoeba

Figure 12.19 Amebae.

Pseudopods

Nucleus

Food vacuole

Amoeba proteus

Entamoeba histolytica

Nucleus

Red blood cells

Apicomplexa

Nonmotile Intracellular parasites Complex life cycles Plasmodium Babesia Cryptosporidium Cyclospora

Figure 12.20 The life cycle of Plasmodium vivax, the apicomplexan that causes malaria. Infected mosquito bites human; sporozoites migrate through bloodstream to liver of human.

Sporozoites undergo schizogony in liver cell; merozoites are produced.

Merozoites released into bloodstream from liver may infect new red blood cells.

Merozoite develops into ring stage in red blood cell.

Intermediate host Ring stage grows and

divides, producing merozoites.

Merozoites are released when red blood cell ruptures; some merozoites infect new red blood cells, and some develop into male and female gametocytes.

Another mosquito bites infected human and ingests gametocytes.

In mosquito’s digestive tract, gametocytes unite to form zygote.

Resulting sporozoites migrate to salivary glands of mosquito.

Sexual reproduction

Female gametocyte

Male gametocyte

Zygote

Gametocytes

Female

Sporozoites in salivary gland

Chapter 12, unnumbered figure A, page 357.

Chapter 12, unnumbered figure B, page 357.

Figure 23.24 The life cycle of Toxoplasma gondii, the cause of toxoplasmosis.

If a pregnant woman accidentally ingests oocysts (contacted when changing a cat litter box), prenatal infection of the fetus may occur.

If humans eat undercooked meat containing tissue cysts, they may become infected.

Definitive host

Tachyzoites Bradyzoites in tissue cyst Sporocysts

Sporozoite

Intermediate hosts

Mature oocyst (10–13 μm x 9–11 μm)

Sporogony

Immature cyst

Immature oocyst is shed in cat feces.

Mature oocysts develop by sporogony and contain two sporocysts, each with four infective sporozoites.

Oocysts can infect many hosts, including mice, domestic animals, and humans, via ingestion.

Sporozoites from ingested oocysts invade animal tissue and develop into bradyzoites within tissue cysts or into tissue-invading tachyzoites.

Cat ingests bradyzoites in tissue cysts of animals, usually mice.

Flagellum

Figure 27.13 A red tide.

Ciliates

Move by cilia Complex cells Balantidium coli is the only human parasite

Figure 12.21 Ciliates.

Pellicle Cytostome

Contractile vacuole Macronucleus Micronucleus Anal pore

Food vacuoles

Cytostome

Paramecium

Vorticella

Figure 12.17 Conjugation in the ciliate protozoan Paramecium.

Macronucleus

Micronucleus

Check Your Understanding Identify three differences between protozoa and

animals. 12-10 Do protozoa have mitochondria? 12-11 Where does Plasmodium undergo sexual

reproduction? 12-12

Slime Molds

12-13 Compare and contrast cellular slime molds and plasmodial slime molds.

Learning Objective

Figure 12.22 The generalized life cycle of a cellular slime mold.

Spore is released.

Cells in spore cap form spores.

Fruiting body with spore cap forms.

Slug stops migrating and begins to form stalk in differentiation stage.

Sheath forms to create migration stage (slug) (0.5 mm).

Ameba germinates from spore.

Stalk (1 mm)

Nucleus

Spore caps

Amebae aggregate.

Amebae move toward cAMP signal given off by one ameba.

Ameba reproduces.

Figure 12.23 The life cycle of a plasmodial slime mold.

Plasmodium grows, distributing nutrients by cytoplasmic streaming.

Haploid gametes fuse, producing zygote.

Gamete germinates from spore.

Spores are released.

Nuclei in spores go through meiosis, forming gametes.

Multinucleate plasmodium forms.

Zygote develops by nuclear division and cell growth.

Plasmodium separates into groups of protoplasm.

Each group forms sporangia on stalks.

Spores develop in sporangia.

Sexual reproduction

Channel of cytoplasmic streaming

Sporangia

Check Your Understanding Why are slime molds classified with amebae and not

fungi? 12-13

Helminths

12-14 List the distinguishing characteristics of parasitic helminths.

12-15 Provide a rationale for the elaborate life cycle of parasitic worms.

Learning Objectives

Kingdom Animalia

Multicellularity All

Cellular Arrangement Tissues and organs

Food Acquisition Method Ingestive; absorptive

Characteristic Features Elaborate life cycles

Helminths

Helminths (Parasitic Worms)

Kingdom: Animalia Phylum: Platyhelminthes (flatworms)

−Class: trematodes (flukes) −Class: cestodes (tapeworms)

Phylum: Nematoda (roundworms)

Characteristics of Helminths

Reduced digestive system Reduced nervous system Reduced locomotion Complex reproduction

Life Cycle of Helminths

Monoecious (hermaphroditic) Male and female reproductive systems in one animal

Dioecious Separate male and female

Egg → larva(e) → adult

Check Your Understanding Why are the drugs used to treat parasitic helminths

often toxic to the host? 12-14 Of what value is the complicated life cycle of

parasitic helminths? 12-15

12-16 List the characteristics of the two classes of parasitic platyhelminths, and give an example of each.

12-17 Describe a parasitic infection in which humans serve as a definitive host, as an intermediate host, and as both.

12-18 List the characteristics of parasitic nematodes, and give an example of infective eggs and infective larvae.

12-19 Compare and contrast platyhelminths and nematodes.

Helminths

Learning Objectives

Figure 12.25 Flukes.

Oral sucker

Intestine

Ventral sucker Testis

Fluke anatomy Clonorchis sinensis

Oral sucker

Ovary Intestine Testes

(b) Life cycle of Schistosoma, cause of schistosomiasis.

Figure 23.28 Schistosomiasis.

Free-swimming cercariae penetrate human skin, losing tail.

Intermediate host

Cercariae are released from the snail.

Cercariae travel through circulatory system to intestinal blood vessels, where they mature into adults.

Adult female flukes lay eggs.

(a) Male and female schistosomes. The female lives in a groove on the ventral (lower) surface of the male schistosome (“split-body”), is continuously fertilized, and continuously lays eggs. The sucker is used by the male to attach to the host.

Eggs reach body of water after being excreted in human feces or urine.

Cercaria (0.33 mm)

Cercaria (0.13 mm)

Definitive host

Female (size: 15–20 mm)

Adult flukes

Egg (0.15 mm)

Miracidium (0.2 mm)

Mouth Sucker Female Mouth

Eggs hatch into free-swimming larvae (miracidia).

Miracidium reproduces in snail, forming several cercariae.

Miracidium penetrates snail.

Figure 12.26 The life cycle of the lung fluke, Paragonimus, spp.

Cercaria

Cercaria (0.5 mm long)

Intermediate host

Cercaria leaves snail and enters crayfish.

Metacercaria (0.25–0.5 mm)

In crayfish, cercaria encysts to produce metacercaria.

Infected crayfish is eaten by human, and metacercaria develops into adult fluke.

Definitive host

Free-swimming miracidium enters snail.

Intermediate host

Miracidium (0.8 mm long)

Miracidium develops in egg and hatches from egg.

Eggs reach water after being excreted in feces.

Adult fluke (7.5–12 mm long)

Inside snail, miracidium develops into redia, which reproduces asexually to produce rediae; several cercariae develop within redia.

1 Hermaphroditic adult fluke releases eggs into human lung.

Sexual reproduction

Sucker

Scolex

Sucker

Genital pore Ovary

Mature proglottid will disintegrate and release eggs

Figure 12.27 General anatomy of an adult tapeworm.

Humans as Definitive Hosts

Definitive Host Taenia saginata

Cysticerci in beef muscle

Intermediate Host

Echinococcus granulosus

Adult in dog

Scolex

Definitive host eats intermediate host, ingesting cysts.

Figure 12.28 The life cycle of the tapeworm, Echinococcus, spp.

Definitive host

Adult tapeworm

Scoleces from cyst attach to intestine and grow into adults.

Adult tapeworm releases eggs.

Egg (30–38 µm)

Hydatid cyst

Larvae develop into hydatid cysts.

Brood capsule Scolex

Larva Eggs hatch, and larvae migrate to liver or lungs.

Intermediate host ingests eggs.

Intermediate host

Human intermediate host ingests eggs. Dead end.

Intermediate host

Sexual reproduction

Figure 12.29a The pinworm Enterobius vermicularis.

Figure 12.30 The heartworm Dirofilaria immitis.

Heartworm

Adult pinworm

Figure 12.29 The pinworm Enterobius vermicularis.

Intestine

Genital pore

Female (8–13 mm long)

Intestine

Genital pore

Spicules

Male (2–5 mm long)

Egg (55 μm long)

Pinworm egg

Testis

Figure 25.26 The life cycle of Trichinella spiralis, the causative agent of trichinellosis.

Ingested cysts develop into Trichinella spiralis adults in the pig’s intestinal wall.

Garbage, including undercooked or raw pork

Meanwhile, other animals eat infected meat that has been dumped.

Capsule

Adult worms produce larvae that encyst in the pig’s muscles.

Section of encysted T. spiralis

Human eats undercooked pork containing cysts that are infective to humans or animals that ingest it.

Trichinellosis in humans; ingested cysts develop into T. spiralis adults. Adults produce larvae that encyst in muscles.

T. spiralis adult

Figure 25.23 An Ancylostoma hookworm attached to intestinal mucosa.

Hookworm

Intestinal mucosa

Check Your Understanding Differentiate Paragonimus and Taenia. 12-16 What is the definitive host for Enterobius?

12-17 What stage of Dirofilaria immitis is infectious

for dogs and cats? 12-18 You find a parasitic worm in a baby’s diapers.

How would you know whether it’s a Taenia or a Necator? 12-19

12-20 Define arthropod vector. 12-21 Differentiate a tick from a mosquito, and name

a disease transmitted by each.

Arthropods as Vectors

Learning Objectives

May transmit diseases (vectors) Kingdom: Animalia Phylum: Arthropoda (exoskeleton, jointed legs)

−Class: Insecta (6 legs) − Lice, fleas, mosquitoes

−Class: Arachnida (8 legs) −Mites and ticks

Mechanical transmission Biological transmission Microbe multiplies in vector

Definitive host Microbe’s sexual reproduction takes place in vector

Figure 12.31 Mosquito.

Figure 12.32 Tick.

Insert Fig 12.33

Figure 12.33 Arthropod vectors.

2.5 mm

Rat flea Human louse Deer fly Kissing bug

Check Your Understanding Vectors can be divided into three major types,

according to roles they play for the parasite. List the three types and a disease transmitted by each. 12-20

Assume you see an arthropod on your arm. How will you determine whether it is a tick or a flea? 12-21

chapter 12faculty.mtsac.edu/cbriggs/12_lecture_presentation.pdf · (opportunistic, systemic...

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