The reproduction form of the bacteria is asexual type. In bacteria, cell growth and reproduction are linked, thus occurring bacterial growth, in which a bacterium grows to a fixed size, occurring then the division through a process called binary fission or bipartition.
Binary fission is a form of asexual reproduction during which the DNA of the bacteria is followed by the division of the cytoplasm , Giving rise to two daughter cells. However, the new bacteria product of the binary division lack of genetic diversity, that is to say, they own the same nucleus.
Growth of bacteria
Bacterial growth occurs in three phrases, which will be influenced by the conditions of the environment in which reproduction and growth will take place (can be natural or artificial). In an optimal environment, these phases are:
1 - Adaptation phase
Also called Lag phase , As the name implies, bacteria are prepared for rapid growth, so during this sentence, the growth of bacteria is slow, and requires a high rate of biosynthesis of the necessary proteins.
2 - Exponential phase
Once the cells have adapted to the environment, the second phase occurs, which is called exponential because of the exponential growth experienced by the cells, ie, the cells grow faster as time passes.
An example of cell growth during this phase is the bacteria known as Escherichia coli, which in an optimal environment reproduce every 20 minutes, ie, a bacterium is divided, giving way to two, thus, in 20 minutes, you are Will give way to four daughters.
During this sentence the nutrients are metabolized at the maximum possible speed, until these are exhausted.
3 - Stationary phase
This phase proceeds to the exponential phase, and occurs as a consequence of the metabolization at very high rates of nutrients, which causes their exhaustion.
Thus, during this phase, the cells considerably reduce their growth, and use non-essential cellular proteins as the energy source, giving rise to the last phase, called the death phase.
Determinants of bacterial reproduction
1 - Temperature
The optimal temperature for the growth of the bacteria will depend on the group to which they belong.
Thus, psychrophilic bacteria find their optimal temperature between -10 and 10 ° C, mesophiles between 25 and 35 ° C, thermophiles at 60 ° and extreme thermophiles at around 100 ° C.
2 - PH
The Hydrogen Potential is a measure of acidity or alkalinity which is measured from 0 to 14, where 0 is the most acidic.
Thus, acidophilic bacteria grow best in an PH between 0 and 6, neutrophils between 6 and 9, and alkalophils between 10 and 14.
3 - Water and osmotic pressure
Bacteria grow better in areas saturated with water. However, an increase in osmotic pressure can cause a bacterium to burst, so a pressure is needed.
4 - Oxygen
Bacteria also require oxygen according to the group to which they belong. In this way, we classify:
- Aerobic, they need oxygen.
- Facultative Anaerobes, which can grow with or without oxygen, but grow better with oxygen.
- Aerotolerant Anaerobes, which grow equally well with or without oxygen.
- Anaerobes bound, which die with the presence of oxygen.
Sexual reproduction and genetic variation
Although the medium of reproduction and growth of bacteria is exclusively by asexual reproduction, this type of reproduction does not produce genetic variation between the new organisms originated.
However, bacteria have genetic means of exchange, which together with binary fission give way to genetic variety.
- Bacterial Conjugation: It occurs when a donor bacterium and a recipient bacterium come into contact with sexual hairs. During this process the donor bacterium transfers a small amount of independent DNA.
- Bacterial transformation: Bacteria can also modify their genes through a process called transformation. This can occur through the acquisition of DNA from the environment, or through a process called transduction, in which a virus called bacteriophage introduces foreign DNA into the chromosome of a bacterium.
General Characteristics of Bacteria
The Bacteria Are microorganisms, ie living beings of small size, which belong to the domain of prokaryotes, which unlike eukaryotic organisms, such as plants and fungi, lack a cell nucleus and are mostly unicellular (made up of a single cell ).
These microorganisms typically measure a few micrometers or microns (thousandths of a millimeter). These come in different forms, such as spheres (cocci), rods (bacilli), corkscrews (vibrios) and propellers (spirils).
Bacteria represent the most abundant organisms of the planet Earth, being found in all the habitats, aquatic and terrestrial.
They are able to grow and reproduce in the most extreme conditions, such as hot and acid springs, the depths of the sea and the earth's crust, or in radioactive waste.
In addition, bacteria are vital in many phases of the nutrient cycle, helping in the recycling of nutrients, as in the process of nitrogen fixation of the atmosphere.
Also, some bacteria capable of resisting freezing temperatures provide nutrients needed to sustain life, converting dissolved components into energy.
It has been determined that there are approximately 30% more bacteria than human cells in the human body. Thanks to the immune system are mostly harmless or beneficial; Although there may be the presence of pathogenic bacteria, which may be responsible for infectious diseases.
Although the term bacterium All prokaryotic organisms, these have now been divided into two groups: Bacteria And archaeas.
These two groups possess considerable differences, among which is the presence of a wall of peptidoglycan in the bacteria.
References
- Bacterium. (2017, June 26). Wikipedia, The free encyclopedia. Date of consultation: 07:34, July 10, 2017 from es.wikipedia.org
- Bacterium. (2017, July 5). In Wikipedia, The Free Encyclopedia. Retrieved 07:34, July 10, 2017, from en.wikipedia.org
- Bacterial growth. (2017, June 14). In Wikipedia, The Free Encyclopedia. Retrieved 07:34, July 10, 2017, from en.wikipedia.org
- Prokaryota. (2017, May 14). Wikipedia, The free encyclopedia. Date of consultation: 07:34, July 10, 2017 from es.wikipedia.org
- Fission (biology). (2017, March 17). In Wikipedia, The Free Encyclopedia. Retrieved 07:34, July 10, 2017, from en.wikipedia.org
- Nutrient cycle. (2017, May 30). In Wikipedia, The Free Encyclopedia. Retrieved 07:35, July 10, 2017, from en.wikipedia.org.