It is a large protist as its length may reach up to 2 mm. It is non-pathogenic as there has been no known Amoeba proteus disease in humans and other animals. Some amoeba-like protists, though, are opportunistic pathogens. Given the opportunity, they may live as a parasite inside a host and cause disease. One of the medically-important amoebas is the Entamoeba histolytica. This species causes entamoebiasis and amebic dysentery to its human and other primate hosts.
It forms a cyst that can be transmitted through ingestion of infected water or food. When swallowed, the cyst will release the trophozoite in the digestive tract and become pathogenic.
It causes flask-shaped ulcers, and eventually, bloody diarrhea. In certain instances, it migrates to the bloodstream, and subsequently, reaches other organs e. Another is the brain-eating amoeba, Naegleria fowleri. The species lives in hot springs, warm freshwater lakes, and rivers. It can turn from a free-living state into a parasite when it enters the body of a host, e. It enters through the nose and penetrates the nasal mucosa.
Later, it migrates to the brain through the olfactory nerves. In the brain, it feeds on brain tissues, e. The nucleus containing the genetic material, DNA, and the mitochondria, well-identified as the "powerhouse of the cell", came about. This tutorial speaks of the evolution of organelles, their diversity, and similarity Read More.
It only takes one biological cell to create an organism. A single cell is able to keep itself functional through its 'miniature machines' known as organelles. Read this tutorial to become familiar with the different cell structures and their functions Organisms employ different strategies to boost its defenses against antigens.
Humans have an immune system to combat pathogens. Read this tutorial to learn the first and second lines of defense that the human body employs. Viruses possess both living and non-living characteristics. This unique feature distinguishes them from other organisms. They require other organisms to host themselves in order to survive and as such, they are regarded as obligate parasites. Learn more about viruses and cell assimilation in this tutorial The sequence of amino acids determines the type of protein.
Protein is synthesized according to the sequence of nucleotides in the expressed DNA strand. For more info on the different types of proteins, read this tutorial Part of the genetic information is devoted to the synthesis of proteins. Read this tutorial for further details Skip to content Main Navigation Search.
Dictionary Articles Tutorials Biology Forum. Table of Contents. Illustration of an amoeba cell with parts: pseudopod, vacuoles , endoplasm , ectoplasm , nucleus , and membrane. The Evolution of Cell Organelles The nucleus containing the genetic material, DNA, and the mitochondria, well-identified as the "powerhouse of the cell", came about. Biological Cell Introduction It only takes one biological cell to create an organism.
Biological Cell Defense Organisms employ different strategies to boost its defenses against antigens. Biological Viruses Viruses possess both living and non-living characteristics. Protein Variety The sequence of amino acids determines the type of protein. Protein Synthesis Part of the genetic information is devoted to the synthesis of proteins. Related Articles No related articles found See all Related Topics. Based on the analyses of SSU rDNA and other DNA sequences, eukaryotic organisms are now organized in a manner that better represents their evolutionary relationships — the phylogenetic tree, according to the Protistology article.
Each lineage in a phylogenetic tree is depicted by a branched structure. In this system, the first levels are known as "supergroups. Animals and fungi are in the group Ophiskontha. Amoeboid protists and some parasitic lineages that lack mitochondria are part of Amoebozoa. Heterotrophic protists — organisms that take in nutrients from other organisms — are part of Excavata, while plants and most other photosynthetic organisms are part of Archaeplastida, according to the Encyclopedia of Evolutionary Biology.
In addition, he noted that amoebas are also present within Rhizaria, Excavata, Opisthokonta for example, Nucleariids, which have filopodia and within the Stramenopiles for example, Labyrinthulids. Amoebas are known to cause a range of human diseases. Amebiasis, or amoebic dysentery, is an infection caused by Entamoeba histolytica, a human intestinal parasite, according to the Centers for Disease Control and Prevention CDC.
According to the National Institutes of Health NIH , Entamoeba histolytica can invade the colon wall and cause colitis, or can cause severe diarrhea and dysentery. Though the disease can occur anywhere in the world, it is most common in tropical regions that have substandard sanitation and crowded conditions.
Contact lens wearers are potentially at risk of a rare infection of the cornea called Acanthamoeba keratitis. According to the CDC , species in the Acanthamoeba genus are free-living and are commonly found in soil, air and water.
Poor contact lens hygiene practices, such as improper storage, handling and disinfection or swimming with lenses, are some of the risk factors for the disease. While the initial symptoms include redness, itchiness and blurred vision, if left untreated the infection will eventually lead to severe pain and can lead to the loss of vision, according to the CDC. Amoebas also cause different infections of the brain. Naegleria fowleri , which has been dubbed "the brain-eating amoeba," causes primary amoebic meningoencephalitis PAM.
Though the disease is rare, it is almost always fatal , according to the CDC. Early symptoms include fever and vomiting, ultimately progressing to more severe symptoms such as hallucinations and coma.
Naegleria fowleri is present in warm freshwater bodies such as hot springs, lakes and rivers, or in poorly chlorinated swimming pools and contaminated, hot tap water. These amoebas enter from the nose and travel to the brain. Another amoeba, Balamuthia mandrillaris, can cause a brain infection known as granulomatous amoebic encephalitis GAE.
Balamuthia infections are rare but are often fatal. Early symptoms include headaches, nausea and low-grade fever,, partial paralysis, seizures and speech difficulties. Balamuthia mandrillaris are found in the soil and can enter the body through open wounds or by breathing in contaminated dust, according to the CDC.
Amoebas can also play host to bacteria that are pathogenic to humans, and they can aid in spreading such bacteria. Bacterial pathogens such as Legionella can resist digestion when consumed by amoebas, according to an article in the journal Front Cell Infection Microbiology. Instead, they are released intact from vacuoles into an amoeba's cytoplasm, where they proliferate.
In such cases, bacteria can become resistant to treatments designed to control their numbers for example, chlorine treatment of water.
Maciver cites the example of cooling towers, where both amoebas and bacteria can grow. Cooling towers tend to expel water droplets, which passersby can breathe in. If bacteria enter the body of an immunocompromised individual in such a manner, they can ultimately infect macrophages, one of the immune system's many defensive cells. Lastly, amoebas are an important part of the soil ecosystem. Amoebas predate on harmful bacteria and regulate their population in the soil, according to a study in the journal Applied and Environmental Microbiology.
Amoebas are also important for recycling nutrients in the soil. According to Maciver, when nutrients become available they are taken up by bacteria, which "effectively lock up all the nutrients in bacterial mass.
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