Micro-organism

see also: Etymology of Micro-organism

The micro-organisms or microbes are living organisms Microscopique S (invisible with the naked eye) and which can thus be observed only using a Microscope.

The term microbe is a generic term and nonscientific aiming at the Bactérie S, Levure S, Protozoaire S, Archaea S and Virus, pathogenic or not. Familiarly, the word microbe indicates a micro-organism (generally a bacterium or a virus) responsible for a disease.

Since 1872 (Ferdinand Julius Cohn) the “Bactéries” are differentiated from the Levure S, of the Moisissure S, the infusoire S or of the parasite S. the word microbe (literally small life ) was introduced by the Chirurgie French N Charles Sédillot in 1878 to indicate all these living beings infinitely smalls, one month before Pasteur and his collaborators makes a communication with the Academy of medicine, the Théorie of the germs and its applications to the Médecine and the Chirurgie, into which living beings microscopic are declared responsible for diseases: “If I had the honor to be a surgeon…” April 30th 1878).

The micro-organisms are present in all the structure of the taxonomic . It is possible to distinguish on the one hand the micro-organisms Procaryote S which do not have a core like the Bactérie S and the Archaea, and on the other hand the micro-organisms Eucaryote S having a core. The microscopic eucaryotes include/understand the Champignon S like the Levure S and the two types of Protiste S, Algue S and Protozoaire S.

The micro-organisms are often described as unicellular some unicellular protists are visible with the naked eye and some multicellular species are microscopic.

The intermediate size of the bacterial cells is from 0,5 to 1 µm, but there exist certain bacteria having a size of more than 50 µm. The cells eucaryotes have a going diameter from 5 to 20 µm.

The unicellular micro-organisms were the first forms of life to be developed on Earth, there is roughly four billion years.

By improving the microscope, Antoine van Leeuwenhoek allowed the discovery of the bacteria, it is the precursor of the study of the micro-organisms and the cellular Biologie.

The micro-organisms are met in all the types of environment present in nature, they colonize all the ecosystem S. They are isolated from the ground, fresh water and marine water, of the air, but also of environment more hostile such as the Pôle S, the Désert S, the Geyser S, at the bottom of the Océan S. the micro-organisms met in extreme environments are described as Extrémophile S. Of many micro-organisms are associated with the Plante S or the animal with which they can maintain the relations of Symbiose, of Commensalisme or of Parasitism. Certain micro-organisms can be Pathogène S, i.e. to involve a disease in the plants or the animals.

Needs for the micro-organisms

The micro-organisms need, to nourish itself:

organic substances:

glucids (sugars): Glucose, Lactose… contribution of carbon and energy.

Use is by breathing (total degradation: gas), is by fermentation (various compounds resulting from the more or less important “cutting” of sugars.

According to the nature of waste, one can distinguish:

* the lactic Fermentation: transformation of lactose into lactic acid by lactic leavens

* the aromatic Fermentation: (lactose) - citrates… transformed into aromatic products (diacétile…)

* the alcoholic Fermentation.

The products of these fermentations are waste and are thus rejected into the medium.

Protids: contribution of nitrogenized substances.

more or less important Degradation of proteins with release of amino-acids, peptides, even ammonia: it is the proteolysis.

Lipids: possibly - contribution of carbon and energy.

Release of fatty-acids: it is the lipolysis.
the quantity of lipids has a protective effect on the destruction of the bacteria by high temperatures.

mineral substances: salts
growth factors: vitamins
water

By the cold, one stops the growth of the majority of the micro-organisms, which will be maintained in a state of dormancy, without multiplication.

The importance of the time of heating allows, for a given temperature, to arrive to a more or less complete destruction; an increase in temperature implying a reduction in the time of heating. The principal heat treatments are the Pasteurization and the sterilization.

When, an adapted and optimal favorable temperature, one allows the development of certain species:

Psychrophilous S: optimal temperature from 12 to 15 °C
Psychrotrophe S: optimal temperature from 25 to 30 °C
Mésophile S: optimal temperature from 30 to 45 °C
Thermophilous S: optimal temperature from 55 to 75 °C

The interaction of different micro-organisms can vary:

the métabiose: succession on the same medium of micro-organisms; the first prepare the “ground” for the following, then stop their multiplication and finally disappear.
the Symbiosis: development on the same medium and at the same time of several microbial species, these species supporting itself mutually.
the antibiose: one distinguishes from them several forms

by competition, related on the number and the virulence of a species; most combative occupying the medium, this one becomes unsuitable with the development of the weakest species.
by inhibition: Antibiotic S
by parasitism: the Bacteriophage S or virus whose multiplication is 25 to 100 times faster than that of the bacteria.

The activity of the micro-organisms in the biosphere, their role in the biogeochemical cycles, is essential for all the life on Earth.

The Microbiologie is the science which studies the micro-organisms.

Seek

2007. A team of biologists of the University of Massachusetts (the United States) discovered a reproducing microbe with 121°C.

Found near to a chimney located in the depths of the Pacific Ocean, the " Stock 121" survived until the temperature of 130°C. It is the alive known organization on ground resisting strongest temperature.

Previously one knew Pyrolobus fumarii which would die after 1 hour of incubation to 121°C.

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