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Plasmodium Species

Members of the genus Plasmodium must colonize both a mosquito and a vertebrate to complete their life cycle. In vertebrates, the parasite develops in liver cells and goes on to infect red blood cells, bursting from and destroying the blood cells with each asexual replication cycle ( [link] ). Of the four Plasmodium species known to infect humans, P . falciparum accounts for 50 percent of all malaria cases and is the primary cause of disease-related fatalities in tropical regions of the world. In 2010, it was estimated that malaria caused between one-half and one million deaths, mostly in African children. During the course of malaria, P . falciparum can infect and destroy more than one-half of a human’s circulating blood cells, leading to severe anemia. In response to waste products released as the parasites burst from infected blood cells, the host immune system mounts a massive inflammatory response with episodes of delirium-inducing fever as parasites lyse red blood cells, spilling parasite waste into the bloodstream. P . falciparum is transmitted to humans by the African malaria mosquito, Anopheles gambiae . Techniques to kill, sterilize, or avoid exposure to this highly aggressive mosquito species are crucial to malaria control.

The micrograph shows round red blood cells, each about 8 microns across, infected with ring-shaped P falciparum.
Red blood cells are shown to be infected with P . falciparum , the causative agent of malaria. In this light microscopic image taken using a 100× oil immersion lens, the ring-shaped P . falciparum stains purple. (credit: modification of work by Michael Zahniser; scale-bar data from Matt Russell)

This movie depicts the pathogenesis of Plasmodium falciparum , the causative agent of malaria.

Trypanosomes

Trypanosoma brucei , the parasite that is responsible for African sleeping sickness, confounds the human immune system by changing its thick layer of surface glycoproteins with each infectious cycle ( [link] ). The glycoproteins are identified by the immune system as foreign antigens, and a specific antibody defense is mounted against the parasite. However, T . brucei has thousands of possible antigens, and with each subsequent generation, the protist switches to a glycoprotein coating with a different molecular structure. In this way, T . brucei is capable of replicating continuously without the immune system ever succeeding in clearing the parasite. Without treatment, T . brucei attacks red blood cells, causing the patient to lapse into a coma and eventually die. During epidemic periods, mortality from the disease can be high. Greater surveillance and control measures lead to a reduction in reported cases; some of the lowest numbers reported in 50 years (fewer than 10,000 cases in all of sub-Saharan Africa) have happened since 2009.

This movie discusses the pathogenesis of Trypanosoma brucei , the causative agent of African sleeping sickness.

In Latin America, another species, T . cruzi , is responsible for Chagas disease. T . cruzi infections are mainly caused by a blood-sucking bug. The parasite inhabits heart and digestive system tissues in the chronic phase of infection, leading to malnutrition and heart failure due to abnormal heart rhythms. An estimated 10 million people are infected with Chagas disease, and it caused 10,000 deaths in 2008.

The micrograph shows round red blood cells, about 8 microns across. Swimming among the red blood cells are ribbon-like trypanosomes. The trypanosomes are about three times as long as the red blood cells are wide.
Trypanosomes are shown among red blood cells. (credit: modification of work by Dr. Myron G. Shultz; scale-bar data from Matt Russell)

Plant parasites

Protist parasites of terrestrial plants include agents that destroy food crops. The oomycete Plasmopara viticola parasitizes grape plants, causing a disease called downy mildew ( [link] ). Grape plants infected with P . viticola appear stunted and have discolored, withered leaves. The spread of downy mildew nearly collapsed the French wine industry in the nineteenth century.

The photo shows a leaf infected with downy mildew (left) and powdery mildew (right). Where the leaf is infected with downy mildew, it is yellow instead of green. Powdery mildew appears as a white fuzz on the leaf.
Both downy and powdery mildews on this grape leaf are caused by an infection of P . viticola . (credit: modification of work by USDA)

Phytophthora infestans is an oomycete responsible for potato late blight, which causes potato stalks and stems to decay into black slime ( [link] ). Widespread potato blight caused by P . infestans precipitated the well-known Irish potato famine in the nineteenth century that claimed the lives of approximately 1 million people and led to the emigration of at least 1 million more from Ireland. Late blight continues to plague potato crops in certain parts of the United States and Russia, wiping out as much as 70 percent of crops when no pesticides are applied.

The photo shows a slice of potato that has browned and appears rotten.
These unappetizing remnants result from an infection with P . infestans , the causative agent of potato late blight. (credit: USDA)

Agents of decomposition

The fungus-like protist saprobes are specialized to absorb nutrients from nonliving organic matter, such as dead organisms or their wastes. For instance, many types of oomycetes grow on dead animals or algae. Saprobic protists have the essential function of returning inorganic nutrients to the soil and water. This process allows for new plant growth, which in turn generates sustenance for other organisms along the food chain. Indeed, without saprobe species, such as protists, fungi, and bacteria, life would cease to exist as all organic carbon became “tied up” in dead organisms.

Section summary

Protists function at several levels of the ecological food web: as primary producers, as direct food sources, and as decomposers. In addition, many protists are parasites of plants and animals that can cause deadly human diseases or destroy valuable crops.

Questions & Answers

What is venation
Mohamed Reply
what is evolution
Anthony Reply
why are you insulting us my niggar?
Emmanuelfray Reply
what is deglutition
Nalumansi Reply
what is biology
Sierrah Reply
biology is a type of science that studies living things
xjuicy_editzz
viruses are composed of what
Daniel Reply
what are some disease caused by virus
Daniel
what are some disease caused by virus
Daniel
what are some disease caused by virus
Daniel
Ebola
Alhassan
Ebola,rabies,polio,hepatitis and small pox
Magoba
Corona (viral disease)
Musoke
viruses kinda in a sense not "living" what mean that a virus molecule that attaches to living organisms cells to destroy/kill them. so to answer your question they are composed/made up of molecules (please note that I am not 100% sure, please feel free to correct me :] )
xjuicy_editzz
what is meiosis
Koosono
what is evolution?
Emmanuelfray
@koosono meiosis is the fusion of gametes (sex cell) to from a zygote and it occurs sexually
xjuicy_editzz
what is the use of biology
Tarkaa Reply
To widen our reasoning abilities about the past and the present events in biology and life at large
Musoke
To understand our biography
Musoke
to study living things
Narh
Among all these which one is the major difference between platyhelminthes and coelenterates? 1. are multicellular 2. have developed a mesoderm 3. reproduce sexually 4. reproduce asexually
Habeeb Reply
what is evolution?
Emmanuelfray Reply
how can you define biology in terms of a burning fire in the bush?
Emmanuelfray
what is a cell
Kagelelo Reply
cell is a functional and unit of life
Sarita
it is the building block n basic unit of life
Narh
describe the process of testing the presence of starch in a leaf
Estel Reply
give me somes of examples.
Manu Reply
give example of what.
Ante
example of what
Elizabeth
what are chromosomes?
Ante
what is Biology
Darkoa
Biology is the study of animals and plants on their characters and death
Okol
No biology is the study of life (living thing's)
Achibiri
Chromosomes refers to one of the small parts like threads in the NUCLEI (central part )of plants and animals cell that carry the GENES
Estel
Yeah okol....Bio-means life and -logy means study/knowledge
Estel
Ecology is the study of
Abdul Reply
Ecology is the study of the interaction of organism in each other and their environment.
Ante
Ecology is the study of the interaction of organism in each other and their environment
Everlove
oh yes!!! exactly
Great
thank much
Ante
what is biome?
Ante
a geographical area with dinstic species
Francis
thanks much it very helpful
Ante
my pleasure
Francis
characteristics of living things
Jane Reply
excretion, movement, sensitivity, reproduction,growth, respiration,nutrition
Estel
what are there function
Ante
what are their function
Ante
what is the two type of reproduction?
Ante
sexual reproduction and asexual reproduction
Abdul
what are their function
Manu
Hi
Olufunmilokun
What is light independent reaction
Benjamin Reply

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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