The 3 types of bacteria (characteristics and morphology)

Beyond its scientific interest, certain types of bacteria are of particular interest to humans in a practical sense, whether for health issues, to develop industrial processes or to be used as markers of environmental quality.

It is a type of microbe that is everywhere and takes a wide variety of forms, besides making viable organisms, which often depend on it (for example, in the case of the human digestive system).

For this reason, it has always been necessary to research criteria for classifying bacteria and to provide tools for their identification. In this article, we will see what these main types of bacteria are, with a brief explanation of each of them.

    What is a bacterium?

    Microorganisms called bacteria can be found everywhere. The immense variety of species has allowed these life forms to colonize almost any point in the world. Nor should we notice that they have been and continue to be essential elements of present-day life; for example, they are in charge of organic decomposition.

    The domain of bacteria is made up of a huge group of generally single-celled living things (made up of a single cell) and prokaryotes. A prokaryote is a type of cell that does not contain membrane organelles inside, and its genetic content is freely found there. These qualities differentiate them from the cells they form, for example, in animals, because they are eukaryotes..

    The general structure of bacteria consists of a cell membrane that separates its interior from the exterior. In addition to that, they also have a cell wall surrounding the membrane, providing greater protection and stability to the bacteria. The sum of the two is known as the bacterial cell envelope, and there are differences in composition and shape between different types of bacteria.

    On the other hand, it should also be borne in mind that examining the size is not a good way to distinguish between bacteria and animals. There are microscopic animals, such as rotifers or tardigrades, which are made up of cells and even have a nervous system.

      The main types of bacteria

      Having criteria to be able to identify bacteria is a very useful tool for their study, even in certain cases essential, such as for identifying the cause of an infection in a human disease. Because of this importance, throughout the history of microbiology (the science that studies microorganisms, including bacteria), many criteria have been generated to achieve a proper classification of prokaryotic cells.

      There are many ways to classify the types of bacteria, for example according to their food source, according to their breathing., By the presence or absence of a certain enzymatic activity (activity of a particular protein), or by its mobility. In addition, for correct identification, it is convenient to combine different criteria.

      One of the most classic and traditional criteria that exist for differentiating between types of bacteria is to do so on the basis of morphological characteristics. Although these are based only on the structure visible under the microscope, they have been very important in the taxonomy of bacteria; even many species of bacteria get their names from the way they present themselves.

      Mainly, this classification considers three fundamental forms:

      1. Coconut

      This type of bacteria is characterized by a spherical cell envelope. In other words, when viewed under a microscope, they are circular cells. In this way, they are easily identifiable and it is easy to distinguish them as individuals and from the environment.

      The subtypes in this category are based on how cells are grouped together, how they arrange themselves next to each other.

      Solitary spherical bacteria are known as the coconut form. However, if instead of one it is two round cells joined together, they are called diplococci. There are more complex junctions that give rise to a chain (streptococci) or irregular shapes that resemble a bunch of grapes (staphylococci).

      2. Bacilli

      The main characteristic of this type of bacteria is that they are shaped like elongated rods.. As in coconuts, the subtypes are based on how the cells are grouped together.

      The solitary form is what is called a bacillus. If two linked cells are found, it is a diplobacillus. In the most numerous unions, they can be differentiated according to whether they are united by the ends forming a chain (estreptobacilos) or by the lateral ones, forming a wall (estacada).

      There is a path between the first two that has been seen; it is not as spherical as a coconut, but neither is it as elongated as a bacillus. This is called cocobacillus.

      3. Helical

      In the latter type of bacteria are grouped different shapes that present / display curvatures in their structure. They can be understood as if they were bacilli that have twisted on themselves, obtaining a helix shape. Thus, it is another of these types of bacteria which is easily recognizable under a microscope, by its appearance.

      They are mainly divided into two rigid spirals (spirals) or flexible spirals (spirochete). The difference is that the spirals that outline your cell envelope either stay the same or may change over time (the spiral moves).

      Interestingly, there is another medium that belongs to this type: the vibrio. This class of bacteria has a silhouette similar to a pea seed. Although not drawing spirals, this type of bacteria is considered to be part of this group, because the curvature of its cell envelope is representative of a genus of bacteria (“Vibrio”) and is not temporary, like it. can occur in bacilli or coconuts.

      Bibliographical references:

      • Alberts and. at. (2004). Molecular biology of the cell. Barcelona: Omega. ISBN 54-282-1351-8.
      • Denamur, E .; Matic, I. (2006). Evolution of mutation rates in bacteria. Molecular microbiology. 60 (4): pages 820-27. Kojima, S .;
      • Blair, DF (2004). The bacterial flagellar motor: structure and function of a complex molecular machine. International Journal of Cytology. 233. pages 93 to 134.
      • Koch, AL (2002). Control of the bacterial cell cycle by cytoplasmic growth. Critical journals in microbiology. 28 (1): pages 61 77.
      • Slonczewski, JL; Foster, JW (2013). Microbiology: an evolving science. New York: WW Norton

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