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By observing bacteria by light or electron microscopy, it is possible to identify with greater or lesser precision, the shape and main morphological characteristics of each bacterium. Thus, the microbiology has managed to group these surprising microorganisms into different types of bacteria according to their shape. You have probably heard of bacilli, cocci, and spirilli, but can you tell how exactly they differ?
If you want to know the names of bacteria known worldwide for the diseases or beneficial that they cause in other organisms, as well as learn what type of group they belong to according to their shape and structure, continue reading this illustrative article by Green Ecologist about the types of bacteria.
What are bacteria - definition and characteristics
Bacteria are single-celled microorganisms made up of a single prokaryotic cell. They are recognized as one of the most primitive groups of living beings on the planet, grouped within the Prokaryotic Kingdom, from the Greek "protos", primitive and "karyotic", nucleus. Among the main characteristics of this extensive and varied group of living organisms, the following stand out:
- The size of the bacteria varies between 0.5 and 5 micrometers (Μm) in length, being necessary the use of optimal microscopy to visualize them.
- Bacteria have enzymatic machinery that allows them to have constant sources of chemical energy to carry out their vital functions.
- The prokaryotic cell structure of bacteria is simple, lacks internal membrane-delimited organelles and has a strong and resistant cell wall, which allows bacteria to survive in different environmental conditions.
- The genetic material of bacteria is made up of circular DNA.
- The vast majority of bacteria are capable of free growth and development, with certain exceptions of groups of bacteria that have forced intracellular life, that is, they need to parasitize other living organisms from which they obtain energy and food to survive.
- The method by which bacteria reproduce is binary fission, a simple process by which the mother cell divides, giving rise to two daughter cells that carry exact replicas of "maternal" DNA.
Find out more about them in these interesting Green Ecologist articles about Are bacteria living things? and the Difference between viruses and bacteria.
Types of bacteria
To know the different types of bacteria that exist, it is necessary to resort to taxonomic classifications that the science of microbiology has been making during the long and detailed study of bacteria. Thus, at present we can differentiate the different types of bacteria according to their morphological structure and cell wall rigidity, being possible to distinguish the following three main types of bacteria:
- Coconuts (with spherical or oval shapes).
- Bacilli (Cylindrical or cane-shaped, both straight and curved).
- Spirils (spiral shape).
In the next sections we will see in detail what are the main characteristics of each of these types of bacteria according to their shape, as well as some examples of bacteria that belong to both groups.
Types of bacteria: cocci
The characteristic spherical or oval shape of coconuts makes that when the bacterium cell divides, it can stay united with another cell after said cell division. In this way, although the bacteria always continue to preserve their cellular independence, they will form different groups depending on the plane of single or multiple division:
- Single division plane: diplococci or chain cocci (genus Streptococcus).
- Multiple planes of division: grouping of cocci in tetrads or clusters (genus Staphylococcus).
Next we will see some names of bacteria cocci, which are known worldwide for the diseases that cause:
- Streptococcus pyogenes (tonsillitis).
- Haemophilus influenzae (flu).
- Streptococcus pneumoniae (pneumonia).
- Neisseria gonorrhoea (gonorrhea).
- Neisseria meningitidi (meningitis).
- Streptococcus mutans (cavities).
- Staphylococcus aureus (osteomyelitis).
Types of bacteria: bacilli
Inside of the group of bacilli it is possible to differentiate different subtypes of bacteria depending on the length and morphological structure of the cells:
- Short, irregularly shaped rods (coccobacilli).
- Long rods with wavy ends (genus Bacillus).
- Comma-shaped curved bacilli (genus Vibrio).
- Bacilli grouped in filaments forming Chinese letters (genus Corynebacterium).
Within the type of bacteria of the bacilli we can find examples of bacteria that maintain both harmful and beneficial relationships with other living organisms.
Bacilli-type bacteria that cause disease:
- Bacillus anthracis (cutaneous anthrax).
- Vibrio cholerae (anger).
Bacilli type bacteria that are part of the bacterial flora, beneficial for animals:
- Lactobacillus casei.
- Lactobacillus acidophilus.
- Lactobacillus bifidus.
Types of bacteria: spirilla
The curious spiral shape that characterizes the bacteria of the group of spirits it is easily recognizable under the light microscope, being possible to distinguish different subgroups according to the number of turns and the structure of said spirals. Thus, the spiral can have a helical shape with a rigid structure, or with a corkscrew shape, the structure being more flexible. This last morphological structure is characteristic of those commonly known as spirochete bacteria.
Here are some names of bacteria who have this kind of helical structures, and diseases associated with such examples of bacteria:
- Treponema pallidum (syphilis).
- Borrelia (causes fever and infections in humans and other animals, using ticks, lice, and other invertebrates as vectors of infection).
- Leptospira (Leptospirosis or Weill's jaundice).
Learn more about bacteria by knowing more about the kingdom of nature in which they are classified, the Monera Kingdom: what it is, characteristics, classification and examples.
If you want to read more articles similar to Types of bacteria, we recommend that you enter our Biology category.
Bibliography- Pérez, M. & Mota, M. (2000) Morphology and bacterial structure. Journal Topics of Bacteriology and Medical Virology. Volume 23.
- Reig, A. L. & Blanco, J. (2002) Prebiotics and probiotics, a beneficial relationship. Cuban Journal of Food and Nutrition, Institute of Nutrition and Food Hygiene. Volume 16 (1), pp: 8-63.
