The bacteria are living unicellular and are prokaryotes . This means that its genetic material, a double-stranded circular DNA molecule, is free in the cytoplasm, not enclosed within a nucleus.
Since microfossils and stromatolites (fossil colonies of bacteria mixed with minerals) have been found in sediments of various geological ages, and even in sedimentary rocks of more than 3.5 billion years , it is claimed that bacteria have existed since very remote times.
Such is the case that they have existed for a long period in the history of the Earth in which there were not even other life forms. In fact, bacteria introduced very significant evolutionary events.
- See also: Virus (biology)
Types of bacteria
It is usually distinguished today in two large groups:
- Bacteria : are represented by those that predominate in today’s natural environment , with the presence of different levels of oxygen and varied metabolisms.
- The Archaea : evolutionarily represent a previous category, with metabolisms specially adapted to extreme environmental situations, such as lack of oxygen (remember that, according to rigorous studies, there was no oxygen on the planet until the vegetables, the great oxygen releasers appeared) , or very saline or very acidic environments and high temperatures.
The great evolutionary success of bacteria is attributed, to a large extent, to its amazing metabolic versatility . It can be affirmed that all the possible mechanisms for obtaining matter and energy exist distributed in the different kinds of bacteria.
- See also: Examples of Microorganisms
Examples of bacteria
|Escherichia coli||Bacillus thuringiensis|
|Bacillus subtilis||Clostridium botulinum|
|Mycobacterium tuberculosis||Clostridium tetani|
|Nitrobacter winogradsky||Pseudomonas aeruginosa|
|Thiobacillus ferooxidans||Falvobacterium aquatile|
|Rodospirillum rubrum||Azotobacter chroococcum|
|Chloroflexus aurantiacus||Neisseria gonorrhaea|
|Enterobacter aerogenes||Haemophilus influenza|
|Serratia marcescens||Yersinia enterocolitica|
|Salmonella typhi||Staphylococcus aureus|
The bacteria are extremely important in nature because they are present in natural cycles of the most important elements for life: the nitrogen, of carbon, of phosphorus, of sulfur, etc.
They can transform organic substances into inorganic and vice versa . Although many bacteria are pathogenic and cause disease in plants and animals (including humans).
Many other are used in various industrial processes , such as food processing and beverage alcohol, of drugs, of antibiotics , etc.
The bacteria are microscopic and outside the membrane that encloses its cytoplasm there is a structure called cell wall. More externally, some bacteria form a gelatinous structure called a capsule.
Bacteria reproduce by binary fission and very quickly, so they are very abundant. Due to their varied metabolism, they can thrive in countless environments such as:
- Fresh and salt water
- Organic material
- I usually
- Fruits and grains
- Animals, both inside and on their surfaces
Many bacteria group together in pairs, chains or packages; They are often mobile; The scourge (long appendix species) is the structure that usually contributes to motility, but not the only one. The set of bacteria in culture is called a colony.