The term “amoeba” is used when referring to simple structured eukaryotic organisms that display characteristic crawling behavior. However, the comparison of genetic content by scientists with various amoeba shows that these organisms need not be genetically intimate.
All living things are divided into eukaryotes and prokaryotes according to their cell structure. In contrast to prokaryotes, eukaryotes are highly organized in cells. Bacteria and Archaea prokaryote while all other creatures eukaryote.
Amoeba are also eukaryotes and mostly consist of a single cell. Amoeba cells, like other eukaryotic cell organisms, have certain characteristic features.
- Their cytoplasm and other cell elements are surrounded by the cell membrane.
- Their DNA is contained in a nucleus in the middle of the cell called the nucleus.
- Finally; They have special structures called organelles that carry out cellular functions, produce energy and carry proteins.
These organelles are common to all eukaryotic cells, but there are a few exceptions. For example, what causes amoebic dysentery in humans Entamoeba Histolytica the parasite whose task is to transport and exchange proteins Golgi apparatus does not have.
According to an article published in the Journal of Biological Chemistry in 2005, it was written that the Entamoeba Histolytica parasite contained Golgi-like structures with similar functions instead of the Golgi apparatus. Sutherland Maciver, who is a lecturer in the biomedical sciences department of Edinburgh University, mentioned that there are also amoebas without mitochondria (organelle responsible for energy).
The reason for this is that the environment in which amoebas live is deprived of oxygen, that is, they live in anoxic conditions. According to an article published in Journal Biochemie in 2014, amoebas without mitochondria have hydrogenosome or mitosome-like organelles that are more primitive than mitochondria for energy production. An example of amoeba without mitochondria is Entamoeba Histolyca, and a free-living amoeba. Mastigamoeba Balamuthi can be given.
In terms of structure, amoeba are similar to developed living cells. Sutherland Maciver of amoeba says “They are like our cells. When they actually move to our white blood cells they look very similar ”he said. Like our white blood cells, amoebas use their pseudopods to move. These short-term limbs allow the amoeb to attach to a surface and move itself in the direction it wants.
According to Maciver, while lying feet move towards one direction, contractions occur at the other end. “As it shrinks, two more things happen, the shrinkage pushes the cytoplasm to the advancing pseudo-feet and also pulls the adhesives that remain on the back of the cell.”He adds. Maciver describes these adhesives as the movement between the amoeba and the surface. This movement with false feet is common in amoebas and distinguishes them from other protists (simple eukaryotic cells that are not plants, animals and fungi).
Different types of amoeba can be seen, which can be distinguished from each other by the appearance of pseudofoot. Fake feet according to Tree Of Life thick and Large while thin and fibrous It can also be like. Another false feet are formed by structures called microtubules that are responsible for the movement of the cell. Reticulopod consists of thin filament-like protrusions tied to a single knot, while actinopod does not consist of microtubule nuclei surrounded by solid and cytoplasm. (Microtubules are structures that make up the cytoskeleton, and they hold or release receptors. They are long, hollow cylindrical structures with protein structure.)
Amoebas also use their lying feet for feeding.
According to an article published in Applied and Environmental Microbiology in 1995, Acanthamoeba castelanii, an amoeba living in the soil, was observed to absorb solids and liquids using its false feet. Absorption of solids phagocytosis called.
It has been observed that amoeba mostly feed on bacteria. Maciver stated that the cell walls of amoebae have receptors that can bind to bacteria and attract them into the cell by phagocytosis. The phagocytosis process of giant amoebae (eg Amobea proteus) is slightly different. Giant amoebas swallow their prey by wrapping it with their lying feet. In both cases, the cell membrane is drawn in while the bacteria foundation It forms an intracellular compartment called. If liquid droplets are in the process of swallowing finocytosis called.
For centuries, organism classification systems, including amoeba, have been based on observable traits and similarities in morphology. Maciver has stated that there is no suitable group to classify amoeba. “Amoebas are rather crawling protozoa.He stated a solution.
Historically, amoebas were merged according to the use of their false feet. Sarcodina It is classified into a single taxonomic group called. According to an article published in the journal Protistology in 2008, it was divided into another subgroup according to the type of false feet. However, the classification system does not show the evolutionary relationship between amoeba and it was not a classification that could be discussed.
Molecular phylogenetics has changed the course of taxonomic classification, especially for eukaryotes. By comparing the similarities and differences in specific DNA sequences within organisms, scientists were able to understand how close amoebas were to each other in evolutionary terms.
Evolutionary Relationships Between Phylogenetic Tree and Living Beings Have Been Determined
Early analysis of ribosomes 18S coded subunit or SSU rDNA He would compare DNA sequences that encode (ribosomes synthesize proteins.) SSU rDNA According to analysis and other DNA sequences, eukaryotic organisms are classified in such a way that their evolutionary relationships are clearer. This classification phylogenetic tree is called.
Each lineage in the phylogenetic tree is shown as branched structures. The first class of this system “supergroupKnown as ”. Fabien Burki, in his article published in Cold Spring Harbor Perspectives in Biology in 2014, describes supergroups as the building blocks of the phylogenetic tree.
Burki also lists 5 supergroups for eukaryotic creatures:
- SAR (Stramenopiles, Alveolata and Rhizaria).
Animals and mushrooms Ophiskontha Located in the supergroup. Amoeboid protists and some parasitic organisms without mitochondria Of Amoebozoa part of it. Ophiskontha and Amoebozoa Amorphea forms a larger group that we call. Heterotrophic protists – organisms that obtain their nutrients from other organisms Excavata plants and photosynthetic organisms while part of the supergroup Archaeplastida It is part of the supergroup.
“If you look at the diversity of protists, you can see that there are amoebas in almost every supergroup, even brown algae have amoebas,” Maciver said. Most amoebas Amoebozoa located in the group. Additionally, they can even be seen in the Rhizaria, Excavata, Opisthokontha and Stramenopilse groups.
The Importance of Amoebas
Amoeba are known to cause various diseases.
Entamoeba Histolyca Causes Amoebic Dysentery
Amoeba dysentery Entamoeba histolyca is a condition caused by an intestinal parasite. Acanthamoeba species are free-living and mostly live in soil, air, and water, according to the Center for Disease Control and Prevention (CDC). Inappropriate storage, touch by hand or swimming with lenses Poor contact lens hygiene practices such as are some of the risk factors for the disease. Symptoms at first rash, itching and blurred vision If untreated infection will eventually to severe pain and vision loss may cause.
Naegleria Fowleri Causes PAM Disease
Amoebas can also cause various brain infections. Naegleria fowleri, also known as brain-eating amoeba PAM to his ailment causes. Although rare, it is a fatal disease. First symptoms, according to the CDC high fever and vomiting when the disease progresses hallucination and coma the probability is rising. Naegleria fowleri can nowadays be found in hot waters such as hot springs, lakes, rivers, poorly chlorinated swimming pools or contaminated, warm fountain waters. This amoeba it enters through the nose and reaches the brain. However, according to the CDC, swallowing water does not cause the disease.
Balamuthia Madrillaris Causes GAE Disease
Another amoeba, Balamuthia madrillaris GAE It causes a brain infection called. This is rare in amoeba but nearly fatal. The CDC stated the killing rate of this amoeba at 89%. At the first symptoms headache, nausea and low fever is seen. In the later stages weight loss, hemiplegia and speech difficulties is seen. Balamuthia madrillaris are found in soil and can enter your body through open wounds or dirty dust.
Amoebas can also host and spread bacteria that are dangerous to humans. When dangerous bacteria such as Legionellacan are consumed by amoebas, amoebas may not be able to digest them. That they can multiply instead foundation They pass into the sections named. In such cases, they can become resistant to antibacterial drugs.
According to an article published in Applied and Enviromental Microbiology in 1995, this event may increase the chances of people getting sick by these bacteria. Where both amoebas and bacteria can grow cooling towers show as example. These cooling towers tend to expel water droplets that passersby can absorb. Hundreds of people passing under cooling towers are in danger of snorting water droplets filled with these amoebae. If amoebas enter the body of an individual with a weakened immune system in this way, they are the fighters of the body’s defense system. macrophage cells they can significantly weaken. Maciver stated that a macrophage cell is very similar to amoeba not only in appearance but also in biochemical and cell biology.
Finally, amoebas are an important part of the soil ecosystem. They keep the bacterial population in balance. In fact, 60% of the amoebas without scab may be responsible for the decrease in the number of bacteria in the fields. Amoebas are also important in the recycling of soil materials. According to Maciver, materials are digested by bacteria when appropriate, but when digested by bacterial amoebas, the materials are released back into the soil in the same way. Maciver “If you have a cycle where the amibian will eat bacteria, the overall effect is to increase the availability of nutrients for the plants, ”He said.