Kingdom Protista

Algae and Protozoans

Protista

Protista are categorized into two taxons:1. Protozoans- animal-like single-celled organisms

2. Algae- plant-like single or multi-celled organisms

Protozoans

Protozoans are protists that have animal-like characteristics. They resemble animals in two ways:

1. They are heterotrophs

2. They have the ability to move

They differ from animals because they are unicellular while animals are multicellular. Protozoans are classified by the way they move. The 4 categories of Protozoans are:

Sarcodinians (move using a pseudopod)

Zooflagellates (move using flagella)

Ciliaphorans (move using cilia)

Sporozoans (form spores)

Sarcodinians

Sarcodinians move by extending lobes of cytoplasm, known as pseudopods. The pseudopod is used for moving and eating. Cytoplasm streams into the lobe and causes the lobe to grow and “ooze”. Because of these pseudopods, sarcodinians have a “blob” like appearance.

Examples of sarcodinians are amoebas and foraminiferans.

pseudopod

Amoeba Foraminiferan

Sarcodinians- Naegleria fowleri

There are a number of diseases caused by sarcodinians. They include:Naegleria fowleri: live in freshwater lakes, natural warm water springs, or streams, and can produce meningitis (brain inflammation of the membranes that covers the brain & spinal cord) in swimmers. Although rare, the disease is often fatal. The amoeba is inhaled and burrows inside the nose, traveling to the brain. Once there, the amoeba eats the neurons (brain cells) and causes meningitis.

Top Picture: image of amoeba

Bottom Picture: Brain tissue infected by Naegleria fowleri. The dark dots are the amoebas. Notice the empty space around the dots; this space used to be tissue before the amoebas digested it.

Sarcodinians- Entamoeba histolytica

Entamoeba histolytica: transmitted thru fecally (from feces) contaminated food and water and causes amoebic dysentery. Symptoms of amoebic dysentery are: abdominal pain and cramps and diarrhea, containing blood, pus, and mucous. Once the amoeba is ingested and inside the small intestine, it releases an enzyme that dissolves tissue. This dissolving allows them to penetrate into the intestinal lining, where lesions develop and can turn into extensive ulcers that cause dysentery with watery stools containing blood. If left untreated, the amoebas can contaminate other parts of the body causing infection in the liver and possibly the brain, lungs, heart, or other tissues, and death can result.

Entamoeba histolytica infecting cells

Liver “eaten” away by the amoebas

Zooflagellates

Zooflagellates move by moving a tail, known as a flagella. Some zooflagellates are free-living freshwater organisms while others live inside organisms- either in a symbiotic relationship or a parasitic relationship.

Examples of zooflagellates are trypasnosoma, leishmania, giardia, trichonympha and chlamydomonas.

flagella

trypanosoma giardia

Zooflagellates- TrichonymphaTrichonympha are a type of zooflagellates that live inside

the gut of termites. They have a symbiotic relationship with termites- they give the termite the ability to break down wood particles and the termite provides a home and food for the zooflagellate. Trichonympha breaks down the cellulose (a type of carbohydrate) in wood and releases the nutrients from the wood that the termite absorbs. If termites did not have Trichonympha, they would not be able to eat wood.

Trichonympha under the light microscope

Left Picture: Termite

Right Picture: Scanning electron micrograph of a Trichonympha

Zooflagellates-TrypanosomaTrypanosoma is a parasitic zooflagellate that causes

African sleeping sickness. Trypanosoma produces a toxin that destroys the host’s red blood cells, causing the host to become weak. The initial bite leaves a distinctive sore spot. Symptoms may include swollen lymph nodes, irritability, fever, severe headache, fatigue, muscle and joint pain, and a skin rash. During the second stage of the disease, the parasite crosses the blood-brain barrier and attacks the central nervous system. Neurological complications include slurred speech, confusion, and difficulty with walking. The zooflagellate is transmitted from host to host through the bite of a tsetse fly.

Trypanosoma infecting red blood cells

Tsetse FlyChild with African sleeping sickness

Zooflagellates-GiardiaGiardia is found in the feces of infected

animals or humans. To become infected, a person must consume contaminated food or water including drinking from streams or rivers. Once ingested, the Giardia adhere to the lining of the small intestine and feed. Symptoms of Giardia include: diarrhea, stomach cramps, bloating, gas, fatigue and weight loss. To avoid Giardia, hikers will boil their water before they drink it to kill the parasite.

Scanning electron micrograph of Giardia

GiardiaGiardia infecting intestinal cells

Ciliaphorans

Ciliaphorans, or ciliates, are protozoans that have bodies covered with short hair like projections called cilia. The cilia beat like oars to propel these protists through the water. Most ciliates live in freshwater habitats but some live in salt water. Most ciliates are not parasitic to humans.

Examples of ciliates are paramecium, tetrahymena and balantidium.

cilia

Ciliates-ParameciumParamecium is one of the most abundant

ciliates found in freshwater. It is covered with cilia that are used to move the paramecium and help it to sweep food into its oral groove. A oral groove is an opening in the cell that allows the organism to consume algae and prey. Once food is in the oral groove, the cell mouth pinches off around the food forming a food vacuole.

Since paramecium live in an aquatic environment, water is constantly diffusing into the cell. To ensure that the cell does not burst in this hypotonic environment, the cell has a contractile vacuole. The vacuole fills with water and when full, it squeezes out the excess water. All protozoans have a contractile vacuole.

Oral groove

Contractile vacuole

Ciliates- Balantidium

Balantidium is the only known parasitic ciliate of humans. It is contracted through the ingestion of water or food that has been contaminated by feces. Balantidium resides in the host’s intestine and feeds on fecal material and cell fragments. The ciliates often invade the lining of the intestines and produce severe ulcers. Symptoms of an infections include: diarrhea, weight loss, nausea, vomiting, abdominal pain, weakness and blood and mucus in feces.

Balantidium

Balantidium in the intestines

SporozoansSporozoans are parasitic protozoans that form spores. When these protozoans

are immature, they form spores with thick, protective walls.

Examples of sporozoans are Plasmodium and Toxoplasma.

Spores inside host cells

Sporozoans-PlasmodiumPlasmodium is a sporozoan that causes malaria in

humans. Mosquitoes are the carriers of the sporozoan. When the mosquito bites a human, the sporozoan infects the liver and multiplies. It then infects the red blood cells, causing them to burst every 48 hours. Symptoms of malaria include high swinging fever, shivering, chills and intense perspiration.

Plasmodium spores bursting from red blood cells

Life cycle of Plasmodium

Sporozoans-ToxoplasmaToxoplasma is a sporozoan that

infects human muscle and nerve tissue. Cats are carriers of the disease and toxoplasmais found in cat feces. Symptoms of the disease are: headache, fever, confusion, seizures, abnormal behavior, and coma.

Toxoplasma SporozoanLife Cycle of Toxoplasma

AlgaeAlgae are protists that have plant-like characteristics

that can perform photosynthesis. They are similar to plants because they contain chlorophyll and produce oxygen as a by-product of photosynthesis. Algae has been broken down into 2 categories- each with sub categories. They are:

1. Uni-cellular algae- Dinoflagellates- Diatoms- Euglenoids

2. Multi-cellular algae- Green Algae- Red Algae- Brown Algae

Uni-Cellular Algae

1. Dinoflagellates: algae with 2 flagella that spin the cells through the water. Most dinoflagellates are saltwater algae. Some have symbiotic relationships with jellyfish, sea anemones and coral by supplying nutrients to these animals.

2. Diatoms: algae that have glasslike cell walls containing silica and contain oil. Because of this oil, the diatoms float in the water. When they die, the silica cell wall sinks to the bottom of the ocean and accumulates. These accumulations can be used in cleaners, abrasives and toothpaste.

3. Euglenoids (Euglena): algae that do NOT have a cell wall, contain flagella and chloroplasts. If euglena is grown in the dark, they loose their chloroplasts and become heterotrophs.

Euglena

Diatoms

Multi-Cellular Algae

1. Green Algae (Chlorophyta):Most green algae live in freshwater, but some are found in shallow places in the ocean. Examples of green algae include: Chlamydomonas, Volvox and Ulva.

2. Red Algae (Rhodophyta): Red algae grows mainly in warm saltwater. Not all red algae is red- it is categorized as red algae because of the other light collecting pigments the algae has other than chlorophyll. Many red algae are found in the tropics around coral reefs.

3. Brown Algae (Phaeophyta): Brown algae grows mainly in cool saltwater. The body of brown algae is known as the thallus and contain air bladdersthat fill with air to allow the algae to float. Kelp is an example of brown algae.

Chlamydomonas ulva volvox

Red algae

Brown algae with air bladders