What is bacteria?

What is bacteria?

Image of bacteria within the depth of the human body.

The word bacteria originated from a Greek word (bakterion), which is a diminutive term for staff or cane. Nevertheless, bacteria can be in the form of helices, spheres, cylinders, spiral threads, rods, or filamentous chains.

Bacteria are prokaryotes, unicellular organisms that lack membrane-bound nuclei and organelles. Bacteria are known to cause disease, fermentation and putrefaction in living beings and organic matter.

Bacteria are everywhere. Bacteria are abundant in the soil, water and air. They are also present in the bodies of humans and animals, and the food we consume.

Bacteria can live in any habitat; indeed, some species survive in outer space. These characteristics make bacteria the most abundant organism in the world: 40 million bacterial cells can live together in just one gram of soil.

The human body houses about ten bacterial cells for each human cell. The immune system allows most bacteria to be harmless or even beneficial (they help digestion, for example). However, certain bacteria can cause serious diseases such as tuberculosis, leprosy and cholera.

The discipline in charge of the study of bacteria is called bacteriology. It is a branch of microbiology, which is the science dedicated to the study of microorganisms. Bacteriology and microbiology belong to the field of biology.

These fields of science have advanced thanks to technological progress, although it is estimated that we know only 1% of the microbes in our biosphere.

Bacteria classification


According to the five kingdom classification, first proposed by biologist Robert Harding Whittaker (1920-1980), bacteria belong to the Monera kingdom.

According to the 3 domains of life classification proposed by microbiologist Carl Woese (1928-2012), bacteria belong to 2 classifications: Archaea domain (any unicellular prokaryotic organism), which includes archaebacteria which are significantly different from other modern life forms, and Bacteria domain, which includes all other groups of bacteria.

Bacteria Types


There are a great variety of bacteria that are important for the survival of human beings and other living beings. An example of this are the colonies of bacteria that live on plantations such as peas, for example. They stay at the root of the pea plant and ensure that it will have what it needs to develop, providing the nitrogen the plant needs to thrive.

The bacteria help in the production of cheese, butter and yoghurt, play an important role in the manufacture of certain medicines and are utilized in the treatment of wastewater. They are also used in leather tanning and tobacco drying.

Bacteria structure


A bacterium is enclosed by a rigid cell wall which is shaping the bacteria, and protecting its cytoplasmic membrane. The cell wall is composed of short chains of amino acids linked by peptide bonds, peptides.

There are certain types of bacteria that rely on an additional layer of protection, a capsule made up of polysaccharides. The cell capsule’s role is to protect bacteria against the offensive of white blood cells, viruses and also to support better adhesion with other bacteria.