How many types of bacteria are there

The 3 types of bacteria (properties and morphology)

Microorganisms known as bacteria can be found everywhere . Due to the immense diversity of species, these life forms could be colonized almost anywhere in the world. Nor do you need to emphasize that they were and are essential elements in life today; For example, they are responsible for organic decomposition.

In addition, some types of bacteria are of particular interest to humans, either for health purposes, for the development of industrial processes, or for their use as markers of environmental quality. Because of this, we have always seen the need to look for criteria in order to classify them and offer tools for identification.


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What is a bacterium?

The domain of bacteria is composed of an immense group of living things, generally unicellular (made up of a single cell) and prokaryotes. A prokaryote is a type of cell that does not contain any membrane-like organelles inside, and its genetic content is free within it. These properties distinguish them from the cells that animals form, for example, since they are eukaryotes .

The general structure of bacteria consists of a cell membrane that separates the inside from the outside. In addition, they also have a cell wall that surrounds the membrane, which means that the bacteria are better protected and stabilized. The sum of the two is known as the bacterial cell envelope, and there are differences in both composition and shape between different types of bacteria.


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The main types of bacteria

Having criteria for identifying bacteria is a very useful tool for studying them, even in some essential cases, such as determining the cause of 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 created for obtaining a good classification of prokaryotic cells.

There are many ways to classify the types of bacteria, such as: B. according to their food source based on their breathing by the presence or absence of a certain enzymatic activity (activity of a specific protein) or by its mobility. For a correct identification it is also useful to combine different criteria.


One of the most classic and traditional criteria that exist for distinguishing bacterial species is to distinguish them from morphological features. Although these are only based on the structure visible through a microscope, they were very important for the taxonomy of bacteria. Even many types of bacteria get their name from the shape they present.

This classification mainly takes three basic forms into account:

1. Cocos

This type of bacteria is characterized by having a cellular envelope with a spherical shape . That is, when observed through the microscope, they are circular cells. The sub-types present in this category are based on the grouping of cells.

The solitary spherical bacteria are known as the coconut shape. However, if it is not one, but two connected round cells, they are called diplococci. There are more complex associations that create a chain (streptococci) or irregular shapes that look like a cluster of grapes (staphylococci).

2. Bacilli

The main characteristic of this type of bacteria is that they are in the shape of elongated rods . As with the coconuts, the subtypes start by grouping the cells.

The solitary form is known as the bacillus. If two cells are found together, it is a diplobacillus. In most joints, they can be differentiated depending on whether they join together at the ends to form a chain (streptobacillus) or at the sides to form a wall (palisade).

There's a shape in between the first two you've seen; It's not as spherical as a coconut, but it doesn't get as long as a bacillus. This is called a cocobacilo.

3. Helicoids

In this last type of bacteria, different shapes are grouped together that have curvatures in their structure . They can be understood as if they were bacilli that have rotated on themselves and are reaching a helix shape.

They are mainly divided into two rigid spirals (espirilos) or flexible spirals (spiroqueta). The difference is whether the spirals that draw its cell envelope stay the same or can change over time (the spiral moves).

Oddly enough, there is another shape that belongs to this type: the Vibrio . This class of bacteria shows a silhouette that resembles a bean seed. Although spirals are not drawn, it is assumed that this type of bacteria falls within this group because the curvature of their cell envelope is representative of a genus of bacteria ("Vibrio") and is not temporary are, as they can occur in the genus bacilli or coconuts.


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