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Monera Kingdom


A very "different" world

By the time Dutch researcher Antonie van Leeuwenhoek (1632-1723) lived, the microbial world was being discovered; It was big news for people in general.

Here's what Leeuwenhoek wrote after observing microorganisms under the microscope:

"I received several gentlemen at my house eager to observe the little eels of vinegar, but some of them were so disgusted with the spectacle that they vowed never to use vinegar. What if those people knew that there are more animals in the human mouth, living among them?" teeth than humans in the whole kingdom? "

They are everywhere!

In ecological terms, animals and plants living in tropical forests and those living on the ocean floor occupy opposite ends of the earth; it is as if they inhabit two distinct "worlds". In their very different environments, there is not a single planet or animal species in common.

However, all the diversity of life in these environments can be overshadowed, that is, by the diversity of bacteria, organisms abundant in both environments and in all other ecosystems on the planet. However, as with other organisms we know only a tiny part of their biodiversity.

Consider 1 gram of ordinary soil - a pinch that we hold between two fingers - and place it in the palm of your hand. We will have a heap of small grains of sand and clay, for example, mixed with decaying organic matter and free nutrients. In addition, we will also have about 10 billion bacteria.

When you hear about bacteria what do you think?

You may answer, "in disease," because many people relate bacteria to disease only.

But bacteria play a very important role in balancing the functions of our bodies and the Earth's ecosystems, and they act, with fungi, as decomposing beings in food webs and chains.

Moneras are all living beings unicellular and prokaryotes, that is, without organized nucleus, individualized by membrane. Its genetic material is dispersed in the hyaloplasma.

At bacteria, microscopic beings of very simple composition, are part of the Monera kingdom. In addition to bacteria, this kingdom is also formed by the cyanobacteria, which in the past were also known as blue algae or cyanophytes.

Note: The term "monera" in the current classification is obsolete. Its members were divided among the kingdoms Bacterium and Archaea. The kingdom Bacterium represents the largest number of species as it encompasses bacteria and cyanobacteria. Already the kingdom Archaea covers a small number of species. Archaea are prokaryote organisms, but they are no longer classified with bacteria because they have characteristics that make them also close to eukaryotes. Despite this new classification, as the term "monera" is still adopted in textbooks, we continue to present its definition here.

In addition to the absence of the individualized nucleus, the moneras cell do not have organelles membranes such as mitochondria and chloroplasts.


Scheme of a bacterial cell

Note in the above scheme that the only organelles in the bacterial hyaloplasma are the ribosomes. In these structures protein production occurs.

Characteristics of moneras

As we have seen, bacteria (from the Greek bakteria: 'rod') are found in all of Earth's ecosystems. These microscopic beings are usually smaller than 8 micrometers (1µm = 0.001 mm).

The shape of these organisms may vary. In the scheme below we see the most common forms found in bacteria.

Although unicellular, bacteria can also exist in groups called colonies. Cocci bacteria, for example, are given the following names according to how they are grouped:

Staphylococci- they cluster in a similar way to a bunch of grapes.

Streptococci - group in a row.

Cyanobacteria also form colonies and can be seen as a dark gelatinous mass.


Cyanobacterial cluster, electron microscope image.