Chapter 12The Eukaryotic members of the

microbial worldMedgar Evers College, CUNY

Prof. Santos

• These organisms include Algae, fungi, protozoa, and large multi-cellular animals such as the arthropods and Helminths.

Algae

• The study of algae is known as phycology.

Properties

• Algae are photosynthetic, they contain chlorophyll A, a light trapping pigment needed for photosynthesis.

• Algae include both unicellular and multi-cellular members.

• Unlike plants, they lack a complex vascular system and have relatively simple reproductive structures.

• Are found in both fresh and salt water

• Make up a vast portion of the phytoplankton found in Earth’s bodies of water.

• Algae can be both microscopic and macroscopic.

• Microscopic algae can be single cell organisms or they can grow as long chains or filaments.

• They can live in groups called colonies such as Volvox.

• Macroscopic algae are multicellular organisms that consists of several parts such as holdfast, stipe, blades, and some have a bladder consisting of gas that allow them to float.

• *The algae cell wall is made up of cellulose and pectin.

• *The red algae cell wall contains carrageenan and agar which are used in food products as stabilizers. Agar is also used to make solid bacterial medium.

Diatoms

• unicellular algae that have silicon dioxide in their cell wall. When these organisms die, their shells sink to the bottom of ocean and does not decompose. Deposits of diatoms are mined for diatomaceous earth. This substance is used for filter systems, abrasives in polishes and insulation.

Disease caused by algae

• Algae do not directly cause disease in humans but can release toxins that when taken in by humans can cause harm.

Examples!1- Gymnodinium breve is a dinoflagellate that

causes red tide in warm waters of Florida and Mexico. It produces a toxin called brevetoxin. Fish ingest the G. breve and then humans eat the fish. Symptoms include tingling sensation in the mouth and fingers, reversal of hot and cold perception, reduced pulse rate, and massive diarrhea.

G. breve

2- Dinoflagellates of the Gonyaulax species cause more serious problems. They produce neurotoxins such as saxitoxin and gonyautoxins.

Shellfish such as clams, mussels, scallops and oysters ingest the dinoflagellates and accumulate the toxins. People that eat the shellfish experience shellfish poisoning.

G.verior

• Symptoms include general numbness, dizziness, muscle weakness, and impaired respiration that can lead to death.

3- Pfiesteria piscicida, this dinoflagellate produces some of the most dangerous toxins known that researchers working with them must take extreme precaution.

Pfiesteria piscicida

4- some species of diatoms can secrete a toxin known as domoic acid that when ingested by humans can cause diarrhea, memory loss, vomiting, nausea, and abdominal cramps.

Diatoms

Protozoa

• Are eukaryotic in nature

• Unicellular

• Are not photosynthetic

• Mostly asexual

• Are classified according to their mode of motility.• three phyla you should know;

Sarcomastigophora, Ciliophora, Apicomplexa, and Microspora.

1-Sarcomastigophora consists of 2 subphylum, Sarcodina and Mastigophora.

A) Sarcodina move by means of pseudopods includes the ameba.

B) Mastigophora move by means of a flagellum.

2-The phylum Ciliophora includes microorganisms that move by means of cilia, tiny hairlike projections.

3- The phylum Apicomplexa includes Plasmodium, Toxoplasma, and Cryptosporidium which cause serious human diseases.

• Are aquatic and terrestrial in terms of habitat

• Lack a cell wall

Diseases

• Please know table 12.2 where they list the infections caused by the major protozoa discussed in the book. Ex’s are

• Malaria caused by Plasmodium

• Amebiasis caused by Entamoeba

• Giardiasis caused by Gardia

• African sleeping sickness caused by Trypanosoma

Fungi

• Unicellular or multicellular• Eukaryotic in nature• Are non-photosynthetic• Cell wall is made up of chitin• Cells are not flagellated

Fungal groupings

1- yeast

• Unicellular

• 3 to 5 um in diameter

• Reproduce by binary fission or budding.

2- Molds• Are filamentous• One filament is called a hyphae.

Hyphae are divided into cells by internal cross-walls called septa.

• A group of hypha is called a mycelium.

Septa

Other properties of fungi

• Are economically important for the food industry such as beer, wine, and cheese production.

• Antimicrobial agents are also produced by fungi such as penicillin and griseofulvin.

Fungi cause human disease in three ways

1-The fungi grows in or on the human body 2- A person might react to a fungal toxin3- A person might develop an allergic

reaction to fungal spores or vegetative cells.

Mycoses

• Fungal diseases

• The name of the individual disease often begins with the name of the causative agent of infection. Ex; histoplasmosis is caused by Histoplasma capsulatum.

Fungal toxins

1- ergotamine, used to treat uterine bleeding

2- Aflatoxins, powerful carcinogen of the liver.

Multicellular parasites

1- *Arthropods

2- Helminths

* Mainly biological vectors or mechanical vectors.

Arthropods

• Include insects and arachnids

• Insects include mosquitoes, lice, and fleas.

• Arachnids include the ticks and mites

• Arthropods are mainly vectors that carry agent of infection that causes diseases such as malaria (plasmodium), yellow fever (flavivirus), plague (Yersinia pestis), typhus (rickettsia), rocky mountain spotted fever and lyme disease and equine encephalitis.

• Mechanical vector- transfers agent from one surface to another.

• Biological vector- are essential part of the life cycle of the pathogen. Example is the anopheles mosquito that transmits plasmodium that causes malaria.

Helminths

• Cause disease

• Three classes; nematodes, cestodes, and trematodes.

Nematodes

• Round worms

• Cylindrical body with a digestive system consisting of 2 openings, mouth and anus

• Free living in soil or water

roundworm

Cestodes

• Tapeworms

• Flat ribbon shaped bodies that are segmented.

• The head or scolex has suckers for attachment.

• No digestive system

• Tapeworms are associated with beef, lamb, pork (Taenia solium) and fish.

Taenia solium

Diphyllobothrium latum

Trematodes or flukes

• Bilaterally symmetrical, flat and leaf-shaped.

• Most are hermaphrodites

• Have suckers for attachment and sucking fluids from host.

Schistosoma mansoni

• Please know table 12. 5 and 12.6 for list of diseases caused by these Helminths.

• Examples are• Ascariasis caused by the roundworm Ascaria,

abdominal pain• Trichinellosis caused by the roundworm Trichinella,

fever, swelling of eyelids, and muscle soreness• Tapeworm disease caused by Diphyllobothrium

latum, a fish tapeworm, no symptoms maybe anemia• Schistosomiasis caused by Schistosoma mansoni,

liver damage and malnutrition and weakness