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7.3.1. Moneras

Kingdom monera

The Monera kingdom is made up of single -celled, prokaryotic organisms. That is, organisms whose DNA is not surrounded by a nuclear membrane, such as bacteria. They are very small organisms, only visible with very powerful microscopes. The main characteristics of the organisms of the kingdom Moneras are:

  • Prokaryotes: They do not have a nucleus or membranous organelles. They are the simplest organisms.
  • Unicellular: All Monera are made up of a single cell.
  • Moneras can live alone or in association with others, forming colonies.
  • They can be autotrophs  and heterotrophs.
  • They can be found in any ecosystem, even in the most extreme conditions.

The Monera kingdom is divided into two groups:

  • Archaebacteria. They live in extreme conditions. They can be thermophilic , halophilic and methanogenic.
  • Eubacteria. They are considered true bacteria.

Structure of prokaryotic cells

Although they were already seen when we talked about the prokaryotic cell, we will review them to remember the characteristics of the organisms of this kingdom.

The structure of the prokaryotic cell is very simple:

  • DNA, bacterial chromosome. DNA is a circular chain that contains the genetic information about the bacterium and is not surrounded by a nuclear envelope. The DNA is free in the cytoplasm, it does not have a nucleus.
  • RibosomesThey are in the cytoplasm. They are responsible for making the  proteins necessary for the prokaryotic cell.
  • CytoplasmIt is surrounded by the plasma membrane and constitutes the internal environment of the cell. Here is the DNA, ribosomes, and all the substances that the cell needs and where all the vital functions are carried out.
  • Plasma membrane. It is the limit of the cell, protecting it and regulating the passage of substances.
  • Cell wall. Hard, rigid wall located on the outside of the plasma membrane that protects and gives shape to the cell. (It is not made of cellulose as in plant cells).
  • Flagella They can have long and few extensions that they use to move.
  • Pili: Extensions that allow them to exchange genetic material with other bacteria.


By Mariana Ruiz LadyofHats. Translated by JMPerez. (Original English version) [Public domain], via Wikimedia Commons

Interactive Activity: Prokaryotes.

Vital functions of bacteria

Nutrition function

The nutrition of bacteria can be:

  • Autotrophs: they make organic matter from the inorganic matter on which they feed. Some, such as cyanobacteria, carry out photosynthesis.

  • Heterotrophs: They create the organic matter they need from organic matter previously synthesized by other living things. Heterotrophic bacteria can be:

Depending on the type of environment in which they live, bacteria can be:

  • Anaerobic: they do not use oxygen for their vital activity. They obtain energy from nutrients without the need for oxygen, through fermentation or other mechanisms. Two types of anaerobic bacteria are distinguished:

    • Facultative anaerobic bacteria: can grow in environments with or without oxygen.
    • Strictly Anaerobic Bacteria: They can only survive in environments without any oxygen.

Relationship function

Bacteria can detect and obtain information from the environment that surrounds them and respond to that environment in order to adapt and survive. Some bacteria do not travel, but others do so using flagella.

Reproduction function

The reproduction of bacteria is asexual, by bipartitionFirst the genetic material is duplicated and then the cell divides in two.

Some bacteria also exchange genetic material, as in the case of conjugation, with other bacteria.

When environmental conditions are adverse, they form a resistant layer, the endospore, under which they remain dormant until environmental conditions become more favourable.

Shapes of bacteria

The form that bacteria have are very varied, although they can be grouped and form colonies. The main types are:

  • Coconut: spherical in shape.
    • Diplococcus : cocci in groups of two.
    • Tetracoccus : cocci in groups of four.
    • Streptococcus : cocci in chains.
    • Staphylococcus : cocci in irregular groups or in clusters.
  • Bacillus: elongated, as if it were a rod.
  • Helical forms:
    • Vibrio: slightly curved and comma-shaped orthographic, bean or peanut.
    • Spiril: rigid helical or spring-shaped.
    • Spirochete: Corkscrew -shaped (flexible helical).

Nombres de los distintos tipos de bacterias según su forma

By Mariana Ruiz LadyofHats [Public domain], via Wikimedia Commons

Resistance of bacteria to antibiotics

Surely you have heard that, lately, bacteria are becoming more resistant to the antibiotics that we use against them and are losing their effectiveness.

The cause of this greater resistance is due to the misuse of drugs, using them in cases of mild infections or diseases caused by viruses. Some bacteria die but the most resistant ones remain, those that have not been affected by the antibiotic, and spread to the rest of the people, meaning that antibiotics have to be increasingly sophisticated to fight them.

The only solution to prevent the increase in bacterial resistance to antibiotics is extreme hygienic measures and decrease the use of antibiotics, using them only when strictly necessary.