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Chapter 12
The Eukaryotes
Kingdom Fungi
Multicellularity All, except yeasts
Cellular Arrangement Unicellular, filamentous, fleshy
Food Acquisition Method Absorptive
Characteristic Features Sexual and asexual spores
Mycology: the study of fungi
Fungi
Table 12.1 Selected Features of Fungi and Bacteria Compared.
Some Things We Like About Good Fungi
• Have been used to produce antibiotics • Essential role in the decomposition of matter • Can be used in food such as mushrooms and truffles • Used to leaven bread • Starter cultures of bread were taken from each batch of
leaved dough and added to the next • 1500 strains of Yeast have been identified
YEASTS
Yeasts are unicellular May become multicellular through connections known as pseudohyphae Yeast measure 3-4 uM in diameter Reproduce asexually by mitosis, but also through budding Saccharomyces cerevisiae converts carbohydrates to carbon dioxide and alcohols via fermentation . The same type of yeast (different strains) are used in Bread and Beer.
FUNGI PLANTS Cell Wall of Chitin Cell Wall of Cellulose Eukaryotic Eukaryotic Often Symbiotic
Lichens
• Mutualistic combination of an alga (or cyanobacterium) and fungus
• Alga produces and secretes carbohydrates; fungus provides holdfast
Figure 12.11b Lichens.
Lichen thallus
Fungus Alga
Cortex
Algal layer
Fungal hyphae
Cortex
Rhizine
Medulla
Economic Effects of Lichens
• Dyes • Antimicrobial (Usnea) • Litmus – litmus paper
Medically Important Phyla of Fungi
• Zygomycota • Microsporidia • Ascomycota
– Anamorphs
• Basidiomycota
Microsporidia
• No hyphae • No mitochondria • Intracellular parasites
– Encephalitozoon intestinalis
Figure 12.8 The life cycle of Encephalitozoon, a microsporidian.
Asexual reproduction
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.
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Ascomycota
• Sac fungi • Septate – septa to divide cells • 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
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Figure 12.3a Aerial and vegetative hyphae.
Aerial hyphae
Aspergillus niger
ASPERGILLUS FUMIGATUS
• Causes black mold on fruits and vegetables • Ubiquitous in soil • Spores can be inhaled causing a serious lung disease, aspergillosis • Has been found in mummies, could have contributed to the curse of King Tut • The toxicity of Aspergillus is due to Ochratoxin A • Gliotoxin excreted by the mold can cause immunosuppression and immunotoxicity in
animals, possibly linked to depletion of macrophages • Serious pathogen in immunocompromised individuals • Voriconazole - treatment
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)
Candida Albicans
• Diploid fungus
Candida Albicans
Natalie Tijerina Sandra Albarracin
General Information Classification: Dimorphic
fungus- can exist in yeast and fungal form (virulence factor)
Genus: Candida Species: albicans Shape: spores and
hyphae(branching tubes that make up the body of a multicellular fungus)
Size: 10-12 µm in diameter
Gram + Growth: reproduces by
budding pH: Needs a slightly
alkaline environment to thrive , a pH about 7.4
Temperature: 37°C, warm and damp environments
Oxygen: Facultative anaerobes
Spores / Hyphae
Diagnosis • Complete medical evaluation and history, with physical exam
that focuses on the area of the body with symptoms • Diagnosis is made based on signs and symptoms, and
clusters of budding yeast • Generally, a doctor takes a sample of the vaginal discharge
or swabs an area of oral or skin lesions, urine, feces, and nail clippings
• Fungal blood and stool cultures for detection of Candida should be taken for patients suspected of having deep organ candidiasis
• Tissue biopsy may be needed for invasive systemic disease.
Route of Transmission/Portal of Entry
• C. Albicans is normally present on the skin and in mucous membranes such as the vagina, mouth, rectum, and digestive tract
• The fungus also can travel through the blood stream in immunocompromised individuals
• Candida can enter newborn infants during or shortly after birth
• This organism is OPPORTUNISTIC- for example, antibiotics kill the good bacteria leaving Candida free to grow
How Candida causes an infection: The infections caused by all species of Candida are
called Candidiasis-most commonly Candida albicans Candida is known to impair immune functioning by
directly and negatively impacting the helper-suppresser ratio of T lymphocytes
Organism causes disease by invading human tissue by means of pseudohyphae (long filaments) which can penetrate intracellular cracks
The overgrowth of Candida is complex and a difficult condition to overcome once it enters the body. It is one of the most highly adaptive organisms, and has the ability to mutate and develop stronger forms of itself
Toxins
Produces toxins -Gliotoxin: inactivates important enzymes, and is
cytotoxic -Acetaldehyde: normal by-product of metabolism,
however excess production of this by Candida can cause impaired neuro-transmission in the brain
Candida Albicans and its toxins can infiltrate and effect any organ or system in the body and can be responsible for a large variety of physical and mental health conditions that we see so commonly in people today
Toxic waste can also be absorbed into the blood stream
Demographics:
Candidiasis is an extremely common infection. Thrush occurs in approximately 2–5 percent of healthy newborns and occurs in a slightly higher percentage of infants during their first year of life.
Over 1 million adult women and adolescent girls in the United States develop vaginal yeast infections each year. It is not life-threatening, but the condition can be uncomfortable and frustrating.
Common factors that can cause infection:
A common cause of Candida albicans fungus is the overuse of antibiotics or oral contraceptives
Steroid hormone medication, ex. Cortisone, or corticosteroids often prescribed for skin conditions such as rashes, eczema
Suppressed immune systems, ex. Patients with diabetes, HIV/AIDS, and that receive radiation or chemotherapy
High sugar and starch diet (yeasts live on sugar, and starches are converted into sugar very quickly during our digestion process)
Areas affected: Candida species can infect tissues in essentially every
body system, producing a wide range of clinical manifestations
is called thrush when it grows in the mouth, especially in infants
shows up on skin as a red, inflamed, and sometimes scaly rash, ex: diaper rash
causes vaginitis, commonly known as a yeast infection causes candidal onchomycosis in the nails can affect the esophagus and the digestive tract Candidal infection of the penis may result from sexual
intercourse with an infected partner
c. Albicans in aids patients
In immunocompromised patients, when body resistance is low as in leukemia or HIV/AIDS, Candida albicans can enter the bloodstream and causes systemic infection
The more debilitated the host the more invasive the disease
Candida albicans is one of several mycoses (fungal disease) that account for most deaths associated with AIDS
So common in HIV+ individuals that their mycoses are part of what defines end-stage AIDS
Treatment: Antifungal medications -- these include oral rinses and tablets,
vaginal tablets and suppositories, and creams. For vaginal yeast infections, medications that are available over the counter include creams and suppositories such as Monistat, Vagistat, and Gyne-Lotrimin. Your doctor may prescribe a pill, Diflucan
Creams combined with low-strength corticosteroids -- reduce inflammation and itching.
The “Candida diet”- detox, probiotics, improve what you eat Most treatments last from 2 - 3 days to 2 weeks. Be sure to
take all medicine exactly as prescribed. If you do not, the same infection could come back, or you could become infected with a new strain of candida.
For severe candidiasis that could be life threatening to someone with a comprised immune system, your doctor may prescribe an IV medication, amphotericin B.
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
Asexual 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.
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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
Kingdom Various
Nutritional Type Chemoheterotroph
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.
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
Asexual reproduction
Female gametocyte
Male gametocyte
Zygote
Male
Gametocytes
Female
Sporozoites in salivary gland
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Schizogony
Toxoplasmosis
• Usually contracted from cats • Causes a mild flu like illness in immunocompetent individuals • Can cause AIDS patients or immunocompromised individuals
to become seriously ill • Parasite can cause encephalitis and neurologic disease as well
as schizophrenia
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.
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Kingdom Animalia
Nutritional Type Chemoheterotroph
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
• 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 Ovary
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)
Eggs
Male
Adult flukes
Egg (0.15 mm)
Miracidium (0.2 mm)
Male
Mouth Sucker Female Mouth
Eggs hatch into free-swimming larvae (miracidia).
Miracidium reproduces in snail, forming several cercariae.
Miracidium penetrates snail.
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Figure 12.26 The life cycle of the lung fluke, Paragonimus, spp.
Cercaria
Redia
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)
Eggs
Inside snail, miracidium develops into redia, which reproduces asexually to produce rediae; several cercariae develop within redia.
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1 Hermaphroditic adult fluke releases eggs into human lung.
Sexual reproduction
Asexual reproduction
Hooks
Sucker
Scolex
Sucker
Genital pore
Ovary
Mature proglottid will disintegrate and release eggs
Figure 12.27 General anatomy of an adult tapeworm.
Neck
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
Asexual reproduction
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Adult pinworm
Figure 12.29a The pinworm Enterobius vermicularis.
Figure 12.30 The heartworm Dirofilaria immitis.
Heartworm
Adult pinworm
Figure 12.29 The pinworm Enterobius vermicularis.
Mouth
Intestine
Ovary
Genital pore
Anus
Female (8–13 mm long)
Mouth
Intestine
Genital pore
Anus
Spicules
Male (2–5 mm long)
Larva
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
Arthropods as Vectors
• 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
Arthropods as Vectors
• Mechanical transmission • Biological transmission
– Microbe multiplies in vector
• Definitive host – Microbe’s sexual reproduction takes place in
vector
Figure 12.31 Mosquito.