CHAPTER 13 - DIVERSITY OF EUKARYOTIC MICROBES AND THE PARASITIC HELMINTHS part 2.

part 2

Algae

• photoautotrophs that lack the roots and stems of plants

• Some are unicellular; others form chains of cells (are filamentous); and a few have thalli.

• mostly aquatic, although some are found in soil or on trees when sufficient moisture is available there.

water

is necessary in algae for physical support, reproduction, and the diffusion of nutrients.

thallus

The body of a multicellular alga is called a

holdfast; stipes; blades

Thalli of the larger multicellular algae, those commonly called seaweeds, consist of branched —, stemlike and often hollow —, and leaflike —.

T

t or f. The thallus lacks the conductive tissue (xylem and phloem) characteristic of vascular plants; algae absorb nutrients from the water over their entire surface.

pneumatocyst

some algae are also buoyed by a floating, gas-filled bladder

fragment

Multicellular algae with thalli and filamentous forms can —; each piece is capable of forming a new thallus or filament.

oomyocytes

fungal-like algae, are chemoheterotrophs.

rRNA sequences

Algae are classified according to their —, structures, pigments, and other qualities

1. Brown Algae 2. Red Algae 3. Green Algae 4. Diatoms 5. Dinoflagellates 6. Water molds

SELECTED PHYLA OF ALGAE

brown algae, or kelp

• are macroscopic; some reach lengths of 50 m

• are found in coastal waters.

• have a phenomenal growth rate

. Algin

a thickener used in many foods is extracted from their cell walls of brown algae

Laminaria japonica

brown alga that is used to induce vaginal dilation before surgical entry into the uterus through the vagina.

red algae

• have delicately branched thalli and can live at greater ocean depths than other algae

• thalli of a few red algae form crustlike coatings on rocks and shells.

• The red pigments enable to absorb the blue light that penetrates deepest into the ocean.

• The agar used in microbiological media is extracted from this

Green algae

• have cellulose cell walls, contain chlorophyll a and b, and store starch, as plants do

• are microscopic, although they may be either unicellular or multicellular

Stramenopila

Diatoms, dinoflagellates, and water molds are grouped into the Kingdom

Diatoms

• are unicellular or filamentous algae with complex cell walls that consist of pectin and a layer of silica.

• store energy captured through photosynthesis in the form of oil.

domoic acid

The diatoms produced —, a toxin that was concentrated in the mussels.

Dinoflagellates

are unicellular algae collectively called plankton, or free-floating organisms

• Their rigid structure is due to cellulose embedded in the plasma membrane.

Karenia brevis, Alexandrium, Gambierdiscus toxicus, Pfiesteria

examples of dinoflagellates

Karenia brevis

• is a dinoflagellate, the algae trapped in the gills of the fish release a neurotoxin that stops the fish from breathing.

Alexandrium

Dinoflagellates in this genus produce neurotoxins (called saxitoxins) that cause paralytic shellfish poisoning (PSP).

red tide

large concentrations of Alexandrium give the ocean a deep red color, from which the name - originates

Gambierdiscus toxicus

causes ciguatera through biomagnification

Pfiesteria

is responsible for periodic massive fish deaths along the Atlantic Coast

water molds, or Oomycota

• are decomposers.

• They form the cottony masses on dead algae and animals, usually in fresh water

Phytophthora infestans, P. cinnamoni, P. ramorum

examples of water molds

Phytophthora infestans

caused the great potato blight (the Irish potato famine or the great hunger)

P. cinnamoni

has infected about 20% of one species of Eucalyptus tree in Australia

P. ramorum

caused “sudden oak death” in California

zoospore

oomycote spores, have two flagella; fungi do not have flagella

Their cellulose cell walls always raised the question about their relationship to algae, and recent DNA analyses have confirmed that oomycotes are more closely related to diatoms and dinoflagellates than to fungi.

what makes oomyocyte more related to algae than fungi

80%

As 75% of the Earth is covered with water, it is estimated that — of the Earth’s O2 is produced by planktonic algae

algal blooms

Seasonal changes in nutrients, light, and temperature cause fluctuations in algal populations; periodic increases in numbers of planktonic algae are called —

• are responsible for seasonal red tides.

Protozoa

• are unicellular, eukaryotic organisms

• means “first animals,” meant to describe animal-like nutrition.

trophozoite

. The feeding and growing stage of protozoa, feeds upon bacteria and small particulate nutrients.

fission, budding, or schizogony.

Protozoa reproduce asexually by

Schizogony

s multiple fission; the nucleus undergoes multiple divisions before the cell divides.

• After many nuclei are formed, a small portion of cytoplasm concentrates around each nucleus, and then the single cell separates into daughter cells

conjugation

• Sexual reproduction has been observed in some protozoa.

• two cells fuse, and a haploid nucleus (the micronucleus) from each cell migrates to the other cell. This haploid micronucleus fuses with the haploid micronucleus within the cell. The parent cells separate, each now a fertilized cell. When the cells later divide, they produce daughter cells with recombined DNA.

gametocytes

Some protozoa produce gametes (—), which are haploid sex cells.

cyst

Under certain adverse conditions, some protozoa produce a protective capsule called a

• permits the organism to survive when food, moisture, or oxygen are lacking, when temperatures are not suitable, or when toxic chemicals are present.

oocyst

The cyst formed by members of the phylum Apicomplexa is called an —

• It is a reproductive structure in which new cells are produced asexually.

1.Feeding Grooves, Euglenozoa, Amebae, Apicomplexa, Ciliates

MEDICALLY-IMPORTANT PROTOZOA

, dinoflagellates and euglenoids

Two chlorophyll-containing groups of protozoa

cytostome

. Ciliates take in food by waving their cilia toward a mouthlike opening called a

Feeding Grooves

Single-celled eukaryotes with a feeding groove in the cytoskeleton have been placed in the Excavata

• Most are spindle-shaped and possess flagella

Giardia intestinalis and Trichomonas vaginalis

example of feeding grooves

Giardia intestinalis

• A parasite without mitochondria

• The parasite is found in the small intestine of humans and other mammals.

• It is excreted in the feces as a cyst and survives in the environment before being ingested by the next host.

Trichomonas vaginalis

• Another human parasite that lacks mitochondria

• has an undulating membrane, which consists of a membrane bordered by a flagellum.

• does not have a cyst stage and must be transferred from host to host quickly before desiccation occurs

Euglenoids

• are photoautotrophs

• have a semirigid plasma membrane called a pellicle, and they move by means of a flagellum at the anterior end.

• also have a red eyespot at the anterior end.

preemergent flagellum.

This carotenoid-containing organelle senses light and directs the cell in the appropriate direction by using a —

facultative chemoheterotrophs

Some euglenoids are

hemoflagellates

blood parasites) are transmitted by the bites of blood-feeding insects and are found in the circulatory system of the bitten host.

ex. Trypanosoma brucei and T. cruzi

Trypanosoma brucei

includes the species that causes African sleeping sickness, , which is transmitted by the tsetse fly.

T. cruzi

causes Chagas disease; transmitted by the “kissing bug”

amebae

move by extending blunt, lobelike projections of the cytoplasm called pseudopods

Entamoeba histolytica

is the only pathogenic ameba found in the human intestine.

Acanthamoeba

growing in water, including water fountain and tap water, -

• can infect the cornea and cause blindness

Balamuthia

• causes brain abscesses called granulomatous amebic encephalitis;

• most often infects immunocompromised people; -

• is a free-living ameba found in water and is not transmitted from human to human

Apicomplexa

are not motile in their mature forms and are obligate intracellular parasites

• characterized by the presence of a complex of special organelles at the apexes (tips) of their cells

Babesia microti, Toxoplasma gondii, Cryptosporidium, Cyclospora cayetanensis, Cystoisospora belli

examples of Apicomplexa

Plasmodium

grows by sexual reproduction in the Anopheles mosquito

sporozoite; merozoites; ring stage

When an Anopheles carrying the infective stage of Plasmodium, called a —, bites a human, sporozoites can be injected into the human. The sporozoites undergo schizogony in liver cells and produce thousands of trophozoites called —, which infect red blood cells. The young merozoite looks like a ring in which the nucleus and cytoplasm are visible. This is called a —

Babesia microti

• Another apicomplexan parasite of red blood cells

• causes fever and anemia in immunosuppressed individuals

Toxoplasma gondii

intracellular parasite of humans; can cause congenital infection in utero

Cryptosporidium lives inside the cells lining the small intestine and

lives inside the cells lining the small intestine and can be transmitted to humans through the feces of cows, rodents, dogs, and cats

Cyclospora cayetanensis

was responsible for 600 cases of diarrhea associated with cilantro in the United States and Canada

Cystoisospora belli

causes cystoisosporiasis, leading to watery diarrhea

Ciliates

have cilia that are similar to but shorter than flagella.

Balantidium coli

The only ciliate that is a human parasite is —, the causative agent of a severe, though rare, type of dysentery

Slime molds

are closely related to amebae and are placed in the phylum Amoebozoa.

cellular and plasmodial.

There are two taxa of slime molds:

Cellular slime molds

are typical eukaryotic cells that resemble amebae. In the life cycle of cellular slime molds, the ameboid cells live and grow by ingesting fungi and bacteria by phagocytosis.

Plasmodial slime molds

exists as a mass of protoplasm with many nuclei (it is multinucleated).

plasmodium

This mass of protoplasm

cytoplasmic streaming

during which the protoplasm within the plasmodium moves and changes both its speed and direction so that the oxygen and nutrients are evenly distributed.

Helminths

are multicellular eukaryotic animals that generally possess digestive, circulatory, nervous, excretory, and reproductive systems

1. They may lack a digestive system.

2. Their nervous system is reduced.

3. Their means of locomotion is occasionally reduced or completely lacking

4. The reproductive system is often complex

The following generalizations distinguish parasitic helminths from their free-living relatives:

phylum Platyhelminthes, the flatworms

are dorsoventrally flattened.

trematodes and cestodes.

The classes of parasitic flatworms include the

Trematodes, or flukes

often have flat, leaf-shaped bodies with a ventral sucker and an oral sucker

• obtain food by absorbing it through their cuticle

Clonorchis sinensis, Paragonimus spp., P. kellicotti, Schistosoma

examples of Trematodes

Cestodes, or tapeworms

are intestinal parasites

scolex

has suckers for attaching to the intestinal mucosa of the definitive host; some species also have small hooks for attachment.

proglottids

are continually produced by the neck region of the scolex, as long as the scolex is attached and alive.

Taenia saginata

the beef tapeworm, live in humans and can reach a length of 6 m. The scolex is about 2 mm long and is followed by a thousand or more proglottids

Taenia solium.

pork tapeworm; Adult worms living in the human intestine produce eggs, which are passed out in feces. When eggs are eaten by pigs, the larval helminth encysts in the pig’s muscles; humans become infected when they eat undercooked pork.

Echinococcus granulosus

Dogs and coyotes are the definitive hosts for this minute (2–8 mm) tapeworm.

hydatid cyst.

cyst of Echinococcus granulosus

• The cyst contains “brood capsules,” from which thousands of scoleces might be produced.

phylum Nematoda, the roundworms

are cylindrical and tapered at each end.

• have a complete digestive system, consisting of a mouth, an intestine, and an anus.

• Most species are dioecious.

• Males are smaller than females

Ascaris, hookworms, and whipworms

Intestinal roundworms are the most common causes of chronic infectious diseases

those in which the egg is infective, and those in which the larva is infective

Nematode infections of humans can be divided into two categories: —

Ascaris lumbricoides, Baylisascaris procyonis, Toxocara canis, T. cati, Trichuris trichiura, Enterobius vermicularis

Eggs Infective for Humans (Nematodes)

Ascaris lumbricoides

• is a large nematode (30 cm in length) that infects over 1 billion people worldwide

• it is dioecious with sexual dimorphism; that is, the male and female worms look distinctly different, the male being smaller with a curled tail.

Trichuris trichiura

whipworm.

• The worms are spread from person to person by fecal–oral transmission or through feces-contaminated food

Toxocara canis

(roundworm in dogs)

T. cati

(roundworm cats)

Enterobius vermicularis

pinworm that spends its entire life in a human host.

• Adult pinworms are found in the large intestine.

• From there, the female pinworm migrates to the anus to deposit her eggs on the perianal skin

Strongyloides; Necator americanus and Ancylostoma duodenale

Larvae Infective for Humans (Nematode)

Strongyloides

A few nematode larvae live in soil and can enter a human host directly through the skin