Kingdom Monera – Characteristics of bacteria

The Monera kingdom is the most primitive of all and comprises some microorganisms such as cyanobacteria, known as bacteria, and archeobacteria (archaea).

All beings belonging to that kingdom are prokaryotes (they do not have a nuclear membrane, the library) and unicellular. Within the group there are autotrophs and heterotrophs.

The cyanobacteria are the only group of prokaryotes that performs photosynthesis with O2 production.

In general, bacteria are very important for the environment, since they decompose organic matter. However, some types are pathogenic and cause disease in living beings.

What are the main characteristics of the Monera kingdom?

The members of the group have some characteristics, such as: cell with cell wall , composed of the chemical substance murein (a heteropolysaccharide linked to peptides).

Cyanobacteria represent the monera kingdom (Photo: depositphotos)

Some representatives, in addition to having a plasma membrane and cell wall, have a capsule that offers greater resistance. They have only one DNA that will form the circular chromosome.

The only ‘organelle’ found within a bacterial cell is the ribosome . They have mesosomes, structures that are responsible for the cellular respiration process, since these individuals do not have mitochondria .

Which living beings (organisms) are part of this?

The organisms of the Monera kingdom are popularly known as “bacteria” , being represented by cyanobacteria (formerly called blue algae) and archeobacteria (archaea).

Cyanobacteria are part of the Bacteria Domain and the Archeas belong to the Archaea Domain.


Morphologically, bacteria can be classified into four categories : coconuts, bacilli, vibrios and spirils. Understand a little more about each of them below!

  • Coconuts:spherical in shape, isolated or forming colonies. They can be diplococci (in pairs), tetrads (square shape), sarcina (in cubic arrangements), streptococci (arranged in rows) or staphylococci (arranged in clusters)
  • Bacilli: rod-shaped
  • Spirils:long, spiral filaments
  • Vibrions:comma-shaped sticks.


In the cytoplasm of the bacterial cell, ribosomes and genetic material are found. In some cases , free DNA particles are found in the cytoplasm or adhered to bacterial chromosomes called plasmids.

Plasmids can contain information that allows the bacteria to break down antibiotics that could kill it. Bacteria are etiological agents of several diseases, such as: cholera, botulism, whooping cough, diphtheria, spotted fever, leprosy, leptospirosis, syphilis, tetanus, tuberculosis, among others.

Some bacteria have locomotion structures, such as cilia and flagella. The lashes will serve both for locomotion and form a kind of bridge, the pili. This, in turn, serves to exchange genetic material during sexual reproduction , in this case conjugation.


The Bacteria Domain is represented by cyanobacteria, popularly known as blue algae . However, they can be of different colors, from bluish green to reddish brown.

The Archaea Domain is represented by methanogens (produce methane gas), extreme halophils (live in aquatic environments with high salinity and in salines) and extreme thermophiles (live in aquatic environments with high temperatures, between 60º C and 150º C).

Kingdom monera: examples and exercises

Follow below some frequently asked questions about the monera kingdom, all of them properly answered:

1. Archeobacteria can be of three types. Which ones are they?

A: Methanogenic, extreme halophils and extreme thermophiles.

2. How important are bacteria?

A: They are important in the decomposition of organic matter, in the ecological relations of mutualism, in agriculture and also in industry through the production of medicines.

3. How does bacteria resist antibiotics?

A: Resistance occurs through genetic mutations. Mutations happen with each cell replication and this acquired mutation is passed on to the next generations.

If the mutation is positive for the success of the bacteria, the antibiotic will have its effect minimized and the microorganisms will become resistant to use.

Heterotrophic bacteria vs. autotrophic bacteria

There are basic differences between these two types of bacteria. Understand more about each of them in the following topics!

Heterotrophic bacteria

  • Saprophytic:obtains food through decomposing organisms, they are called decomposers. Recycle organic compounds
  • Parasites:obtain food by parasitizing the individual host
  • Mutualistic relations:obtains the food, but does not harm its host. Eg bacteria that settle in the cow’s stomach and digest cellulose.

Autotrophic bacteria

  • Photosynthesis :there is no presence of chloroplast. In this photosynthesis, CO2 and sunlight are used for simpler organic matter synthesis and sulfur release
  • Chemosynthesis: itis a kind of photosynthesis without the need for light, the energy used is that of some inorganic compound, where energy is obtained from the connection of the compound that will react with oxygen.


The microorganisms of the Monera kingdom are unicellular, anaerobic (which do not use oxygen as a source of energy production) or aerobic (which need oxygen for energy production, in this case, known as ATP).

These beings can still be classified as autotrophic (photosynthetic or chemosynthetic) or heterotrophic. The organisms of this kingdom are present in all environments: in the air, in the water, in the soil, being able to live isolated or in colonial groups.

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