Chapter 5- Part 2

Chapter 5- part 2

A Survey of Eukaryotic Cells & Microorganisms The Protists

Plant-like Animal-like

1) Single celled or multi- 1) Single celled, lack tissues cellular 2) Are like animals because: 2) Photosynthesize with chlorophyll a a) heterotrophic nutrition;

b) motility Algae

• Photosynthetic organisms

• Microscopic forms are unicellular, multi-cellular, filamentous

• Macroscopic forms are colonial and multicellular

• Contain chloroplasts with chlorophyll and other pigments

• Cell wall

• May or may not have flagella Algae

• Most are free-living in fresh and marine water – plankton

• Provide basis of food web in most aquatic habitats

• Produce large proportion of atmospheric O2

• Dinoflagellates can cause red tides and give off toxins that cause food poisoning with neurological symptoms

Protozoa • Diverse group of 65,000 species, most are harmless, free-living in a moist habitat

• Vary in shape, lack a cell wall

• Most are unicellular; colonies are rare

• Some are animal parasites and can be spread by insect vectors

• All are heterotrophic – lack chloroplasts

• Cytoplasm divided into ectoplasm and endoplasm

• Feed by engulfing other microbes and organic matter

Protozoa • Most have locomotor structures – flagella, cilia, or pseudopods

• Exist as trophozoite – motile feeding stage

• Many can enter into a dormant resting stage when conditions are unfavorable for growth and feeding – cyst

• All reproduce asexually, mitosis or multiple fission; many also reproduce sexually – conjugation Protozoal identification • Classification is difficult because of diversity • Simple grouping is based on method of motility, reproduction, and life cycle

1.Mastigophora – primarily flagellar motility, some flagellar and amoeboid; sexual reproduction

2.Sarcodina – primarily amoeba; asexual reproduction by fission; most are free-living

3.Ciliophora – cilia; trophozoites and cysts; most are free-living, harmless

4.Apicomplexa – motility is absent except male gametes; sexual and asexual reproduction; complex life cycle – all parasitic

Pathogenic Protozoa

Sarcodina

Ciliophora

Mastigophora

Apicomplexa Sarcodina

Food vacuoles Trophozoite Nucleus Nucleus

Red blood cell

Contractile Pseudopods vacuoles

• Alternates between a large trophozoite, motile by means of pseudopods and a smaller nonmotile cyst Cyst

• Trophozoite has a large nucleus and lacks most other organelles Entamoeba histolytica and Amebiasis

• Asymptomatic in 90% of patients • Ameba may secrete enzymes that dissolve tissues and penetrate deeper layers of the mucosa • Causing dysentery, abdominal pain, fever, diarrhea, and weight loss • Carried by 10% of world population Entamoeba histolytica and Amebiasis Amebic infections of the brain • Caused by Naegleria fowleri and Acanthamoeba • Ordinarily inhabit standing water • Primary acute meningoencephalitis is acquired through nasal contact with water or traumatic eye damage • Infiltration of brain is usually fatal Mastigophora: Giardia lamblia and Giardiasis Nucleus Ventral depression

Nuclei

http://www.cdc.gov/parasites/giardia/ Trophozoite Cyst • Pathogenic flagellate • Unique symmetrical heart shape with concave ventral surface that acts like a suction cup • Cysts are small, compact, and multinucleate • Reservoirs include beavers, cattle, coyotes, cats, and humans • Cysts can survive for 2 months in environment https://web.stanford.edu/class/humbio103/ParaSites2003/Giardia/GIARDIA2.htm

Giardia lamblia and Giardiasis Usually ingested with water and food ID 10 to 100 cysts. Cysts enter duodenum, germinate, travel to jejunum to feed and multiply Causes giardiasis – diarrhea, abdominal pain Diagnosis is difficult because organism is shed in feces intermittently Treatment: quinacrine or metronidazole Agent is killed by boiling, ozone, and iodine

Mastigophora: Trypanosoma sp.

• Pathogenic flagellates

• Trypanosomes – Trypanosoma

• T. brucei – African sleeping sickness

• T. cruzi – Chaga’s disease; South America

Trypanosoma brucei and African Sleeping Sickness

Spread by tsetse flies

Two variants of disease caused by 2 subspecies:

T.brucei. gambiense – Gambian strain; West Africa

T.brucei. rhodesiense – Rhodesian strain; East Africa

Biting of fly inoculates skin with trypomastigotes, which multiplies in blood and damages spleen, lymph nodes, and brain Mastigophora: Trypanosoma cruzi, Chagas disease

Causes Chagas disease

Reduviid bug (kissing bug) is the vector

Infection occurs when bug feces is inoculated into a cutaneous portal

Local lesion, fever, and swelling of lymph nodes, spleen, and liver

Reduviid bug (Triatoma infestans) Mastigophora: Trypanosoma cruzi, Chagas disease • Heart muscle and large intestine harbor masses of amastigotes

• Chronic inflammation occurs in the organs (especially heart and brain)

Abnormal enlargement Amastigotes

Cardiac muscle fibers Mastigophora: Leishmania donovani and Leishmaniasis • Leishmaniasis – zoonosis transmitted among mammalian hosts by female sand flies that require a blood meal to produce eggs

• Endemic to equatorial regions

Mastigophora: Leishmania donovani and Leishmaniasis

Cutaneous-oriental sore, Baghdad boil – localized ulcerated sore

Systemic (visceral) – high intermittent fever; weight loss, enlarged spleen, liver, and lymph nodes

Kala azar is the most severe and fatal form if untreated

Ciliophora

Bodies covered with cilia

Most ciliophora members are not pathogenic to humans

Food E.g. Paramecium vacuoles

Oral cilia in groove

Macronucleus Micronucleus Gullet Water vacuole

Lack locomotor organelles in the trophozoite state

Alternate between sexual and asexual phases and between different animal hosts

Most form specialized infective bodies that are transmitted by arthropod vectors, food, water, or other means

Plasmodium

Toxoplasma

Cryptosporidium Plasmodium: The agent of Malaria

• Dominant protozoan disease • Obligate intracellular sporozoan • 4 species: P. malariae, P. vivax, P. falciparum, and P. ovale

• Female Anopheles mosquito is the primary vector; blood transfusions, mother to fetus

• 300-500 million new cases each year and 2 million deaths each year Apicomplexa: Toxoplasma gondii and Toxoplasmosis

Intracellular apicomplexan parasite with extensive distribution

Lives naturally in cats that harbor oocysts in the GI tract

Acquired by ingesting raw meats or substances contaminated by cat feces

Most cases of toxoplasmosis go unnoticed except in fetus and AIDS patients who can suffer brain and heart damage

Parasitic Helminths

Multicellular animals, organs for reproduction, digestion, movement, protection

Parasitize host tissues

Have mouthparts for attachment to or digestion of host tissues

Most have well-developed sex organs that produce eggs and sperm

Fertilized eggs go through larval period in or out of host body Parasitic Helminths Major groups of parasitic Helminths Major groups of parasitic Helminths

1. Flatworms – flat, no definite body cavity; digestive tract a blind pouch; simple excretory and nervous systems

• Cestodes (tapeworms)

• Trematodes or flukes, are flattened, non-segmented worms with sucking mouthparts

2. Roundworms (nematodes) – round, a complete digestive tract, a protective surface cuticle, spines and hooks on mouth; excretory and nervous systems poorly developed Helminth classification and identification • Classify according to shape, size, organ development, presence of hooks, suckers, or other special structures, mode of reproduction, hosts, and appearance of eggs and larvae

• Identify by microscopic detection of worm, larvae, or eggs Distribution and importance of parasitic worms

• Approximately 50 species parasitize humans

• Distributed worldwide; some restricted to certain geographic regions with higher incidence in tropics

• Acquired through ingestion of larvae or eggs in food; from soil or water; some are carried by insect vectors

• Afflict billions of humans https://www.bcm.edu/education/schools/national-school-of-tropical-medicine/ Nematode (Roundworm) infestations • Most abundant animal groups; 50 species that affect humans

• Elongated, cylindrical worms with protective cuticles, circular muscles, a complete digestive tract, and separate sexes

• Divided into intestinal nematodes and tissue nematodes

Ascaris lumbricoides A large intestinal roundworm. Indigenous to humans

Most cases in the U.S. occur in the southeastern states

Ascaris spends its larval and adult stages in humans; release embryonic eggs in feces, and are spread to other humans; food, drink, or contaminated objects

Ingested eggs hatch into larvae and burrow through the intestine into circulation and travel to the lungs and pharynx and are swallowed

Adult worms complete cycle in intestines and reproduce – 200,000 eggs/day Hookworms

• Characteristic curved ends and hooked mouths

• Necator americanus and Ancylostoma duodenale

• Humans shed eggs in feces, which hatch into

filariform larvae and burrow into the skin of CDC bare feet

CDC Hookworms • Larvae travel from blood to lungs, proceed up bronchi and throat and are swallowed Male Egg stages in feces (diagnostic stage) • Worms mature and reproduce in small intestine and complete the cycle Female • May cause pneumonia, nausea, vomiting, cramps, and bloody diarrhea Adults

• Blood loss is significant – anemia

• Cause chronic, deforming disease

• Wuchereria bancrofti

• Elephantiasis

Trematodes or Flukes Flatworms with ovoid leaflike bodies Oral sucker

Have digestive, excretory, neuromuscular, and reproductive Ovary systems

Lack circulatory and respiratory Testis systems

Digestive Animals such as snails or fish are gland usually the intermediate hosts and humans are the definitive hosts

Three types: Blood flukes, liver flukes, Lung flukes Blood Flukes: Schistosomes • Schistosomiasis – prominent parasitic disease • Schistosoma mansoni, S. japonicum, S. haematobium • Adult flukes live in humans who release eggs into water; early larva (miracidium) develops in freshwater snail into a 2nd larva (cercaria) • This larva penetrates human skin and moves into the liver to mature; adults migrate to intestine or bladder and shed eggs, giving rise to chronic organ enlargement Cestode (Tapeworm) Infestations

• Flatworms

• Long, very thin, ribbonlike bodies composed of sacs (proglottids) and a scolex that grips the intestine

• Each proglottid is an independent unit adapted to absorbing food and making and releasing eggs

• Taenia saginata • Taenia solium

Taenia solium tapeworm scolex displaying four suckers and two rows of hooklets.