Amoebozoa is one of the broadest phyla of the Protista Kingdom. It houses a large number of organisms, of the most varied characteristics. Flagellate cells can be found, with a protective shell, with a variable number of nuclei, among others.
This phylum in turn includes two subphiles: Lobosa and Conosa. Within the first, the classes Cutosea, Discosea and Tubulínea are grouped. In the second the classes Variosea, Archamoeba and Mycetozoa are grouped.
Amoeba proteus. Source: By Cymothoa exigua, from Wikimedia Commons
Also within this edge are free-living organisms, symbionts and even parasites of some mammals, including humans. Many can cause pathologies such as dysentery and granulomatous amoebic encephalitis, among many others.
Although it is true that many of the species that belong to this phylum have been very well studied and many aspects are known about them, such as Amoeba proteus, there are also others that remain practically unknown.
This is why the Amoebozoa phylum continues to attract the attention of many specialists, so that in the future many more contributions of this phylum to environmental balance will be discovered.
Taxonomy
The taxonomic classification of the phylum Amoebozoa is as follows:
Domnio: Eukarya
Kingdom: Protista
Phylum: Amoebozoa
Morphology
The organisms of this phylum are eukaryotic unicellular. Internally, it can be seen that the cell is divided into two zones, a spherical and transparent one known as ectoplasm and an internal one known as endoplasm.
Similarly, depending on the species, cells can have several presentations: sometimes they have a covering made up of a simple membrane or a layer of scales; they may also have a harder and more rigid shell, known as a shell, or they may simply not have any of these structures.
A curious fact is that, in the case of those with a shell, it can be made from organic molecules secreted by the same organism. However, there are others that are formed as a product of some particles that are added, such as diatom shells or sand cements.
Likewise, some species exhibit cilia on their surfaces. Within this group you can find organisms with a single cell nucleus, with two or many more.
General characteristics
As mentioned, Amoebozoa organisms are unicellular, which implies that they are made up of a single cell.
As this is a fairly broad edge, here you will find free-living organisms, with a commensal lifestyle and parasites. For example, Naegleria foweleri is free-living, Entamoeba coli is a commensal of the large intestine, and Balamuthia mandrillaris is a disease-causing parasite in humans.
With regard to locomotion, most of the members of this edge move making use of extensions of their body, known as pseudopods.
Due to the wide variety of organisms in this phylum, the process of displacement varies from one species to another. There are some in which the cell becomes a single pseudopod to move, as well as others that have the ability to form multiple pseudopods.
In its life cycle several forms can be seen involved, such as the trophozoite, the cyst and in very specific cases, the spores.
Size is also another parameter that is highly variable in the Amoebozoa phylum. There are organisms so small that they measure 2 microns and there are others so large that they can reach up to several millimeters.
Habitat
Members of the phylum Amoebozoa are found primarily in freshwater bodies. They can also be found at ground level. There are a few that live in the human body as symbiotes or commensals.
Some others function as human pathogenic parasites. In short, the Amoebozoa phylum is versatile, as its members can be found in diverse environments around the world.
Nutrition
Members of the phylum Amoebozoa use phagocytosis for their nutrition and feeding process. In order to achieve this, pseudopods play a vital role in the uptake of food and nutrients.
When it recognizes a food particle, the pseudopods surround it and enclose it in a kind of bag that is trapped inside the cell.
Digestion and degradation is carried out by a series of digestive enzymes that act on food, breaking it down and converting it into molecules that are easily assimilated.
Later, by simple diffusion, these fragmented nutrients pass to the cytoplasm, where they are used for various processes specific to each cell.
In the vacuole remain the residues of the digestive process, which are going to be released outside the cell. This release occurs when the vacuole fuses with the cell membrane to come into contact with the outer space of the cell and get rid of waste and undigested particles.
Breathing
Although it is true that the organisms that are part of this edge are varied and different, they also coincide on certain key points. Breathing is one of them.
These organisms do not have specialized organs for the breathing process. Therefore they resort to simpler mechanisms to satisfy their oxygen needs.
The mechanism by which respiration occurs in cells of the genus Amoebozoa is direct respiration, based on passive transport of the simple diffusion type. In this, oxygen moves inside the cell, crossing the plasma membrane.
This process occurs in favor of the concentration gradient. In other words, the oxygen will go from a place where it is highly concentrated to another where it is not. Once inside the cell, oxygen is used in various cellular processes, some of which are a source of energy.
Product of the use of oxygen, carbon dioxide (CO2) can be formed, which can be toxic and harmful to the cell. Therefore, CO2 must be expelled out of this, a simple process that is carried out, once again, with cell diffusion.
Reproduction
The most frequent method of reproduction among organisms of this phylum is the asexual form. This does not involve any type of genetic material between cells, much less the fusion of gametes.
This type of reproduction consists in that a single progenitor cell will generate two cells that are genetically and physically exactly the same as the one that originated them.
In the case of members of the phylum Amoebozoa, the most frequent asexual reproduction process used is binary fission.
The first step in this process is the duplication of genetic material. This is necessary because each resulting cell must have the same genetic makeup as the parent.
Once the DNA has been duplicated, each copy is located at opposite ends of the cell. This begins to lengthen, until its cytoplasm begins to undergo a strangulation, until it is finally divided, giving rise to two exactly the same cells.
There are a few species of this phylum that reproduce sexually. In this case, a process called syngamy or gamete fusion occurs that involves the union of sex cells.
References
- Adl et al. 2012. The revised classification of eukaryotes. Journal of Eukaryotic Microbiology, 59 (5), 429-514
- Baker, S., Griffiths, C. and Nicklin, J. (2007). Microbiology. Garland science. 4th edition.
- Corliss, JO (1984). "The Kingdom Protista and its 45 Phyla". BioSystems 17 (2): 87–126.
- Schilde, C. and Schaap P. (2013). The Amoebozoa. Methods in Molecular Biology. 983. 1-15
- Tortora, G., Berdell, F. and Case, C. (2007). Introduction to Microbiology. Editorial Médica Panamericana. 9th edition.