Microbiological culture

A culture of microorganisms produced by the cultivation of microorganisms. The organisms grow by cell division in an appropriate culture medium for it under controlled conditions, such as a certain temperature, and the presence or absence of oxygen. Using a microorganism culture can be the type of organism used to investigate closer. For example, a bacterial culture can be isolated from a sample in order to detect the bacteria contained therein. This may relate to pathogens, but just to microorganisms that are naturally present eg in a soil sample.

Microorganism cultures are used for many purposes. You will find in biotechnological production processes use to produce enzymes or vitamins, for example; to produce in the pharmaceutical biotechnology, for example, to produce antibiotics, or in genetic engineering, genetically modified organisms with specific properties.

In microbiology, a distinction different culture techniques, of which the " solid " gel culture media include the pure culture, enrichment culture, liquid culture and the culture of the most important. Furthermore, there is the field of cell culture, this describes cultures of eukaryotic cells, so the animal or plant cells.

Pure culture

Goal of a pure culture is the growth of a clone of a particular organism, excluding any individuals of other species or strains of organisms. A pure culture is also referred to as axenic culture. The other undesirable organisms are called contaminants. Only in pure culture can maintain standardized conditions and micro-organisms are examined with respect to their metabolic and physiological characteristics.

Enrichment culture

An enrichment culture provides growth conditions that are more favorable for a particular microorganism or a particular physiological group of microorganisms than for other microorganisms, these selectively to enrich the target, while the growth of other organisms is slower or is inhibited. So specifically, anaerobic microorganisms can be enriched, for example, in soil samples by applying culture techniques that exclude the access of oxygen. Also in the activated sludge basin of a biological wastewater treatment plant conditions are created that promote the growth of certain bacteria (eg, by Zoogloea sp.) Suppress and the other species. The principle of enrichment culture was developed by Martinus Willem Beijerinck independently and Sergei Nikolayevich Winogradski.

Liquid culture

In liquid cultures, microorganisms are cultured in liquid media. For a growth-promoting aeration ( oxygen supply ), the culture vessels are usually automatically shaken. The vessels used, such as, for example, Erlenmeyer flasks, containing so-called baffles inwardly directed projections to promote mixing. A liquid culture provides the advantage that one can produce larger amounts of it in order to use them in a bioreactor, for example, in biotechnological production. But even small amounts of a liquid culture are used, usually in test tubes - called in microbiology as a culture tube. They are used for quantification of microorganisms according to the method of the "most probable number " ( "Most Probable Number ", see MPN method) or to check for certain metabolic activities of microorganisms to their identification in the context of a "colorful series".

Culture on gel culture media

A gel culture medium is prepared by adding a culture medium, a gelling ( " solidifies " ) substance is added, which does not serve as a food source to the respective organism. The gelling agent most often used is agar ( agar-agar ), other strength agent are gelatin, Gelrite, and silica gel.

The organisms may be placed on the surface of the gel or in the interior thereof to the growth and propagation. The advantage of a culture or in gel culture media is that most microorganisms to it or can not move it, so that they form on or in gel culture media colonies. Which is used to produce pure culture for research to obtain relatively small amounts of micro-organisms and to quantitate microorganisms.

Fractional dilution plating

Fractionated the dilution plating is a special technique to apply microbial samples on the gelled culture medium to obtain single colonies standing required for identification. Here, slalom -like run with the infected inoculation loop on the surface of the medium, without injuring them, and each interrupted twice to sterilize the inoculation loop and to start a new faction. With the inoculating loop the end of the previous fraction is to once each crossed and further slalom -like formed a new faction.

In the picture you can both track down the inoculating loop still visible, as well as the effect of Verdünnungsausstrichs: In the first fraction, bottom left, everything is still overgrown by a large colony; this alone is not suitable for identification of most microorganisms. In the second fraction above the left single colonies are already seeing in the last fraction on the right side there are only single colonies. Single colonies arise from a single cell or a few similar cells that have solved there by the inoculation loop.

Under certain circumstances, especially when specific Differentialnährböden, individual colonies may allow identification of the microorganism on the basis of shape, surface, edge boundary and color. Escherichia coli can be seen for example on Endo agar at tubby single colonies dunkelviolettrot and metallic shine. An accurate identification is, however, possible by particularly expensive and time-consuming DNA analysis only by other, minor consuming tests and in difficult cases.

By taking a sample from a single colony and further isolation by plating on a nutrient agar, you can win a pure culture of a microorganism, and these continue to multiply. This approach assumes by this procedure from an individual who is in the pure culture of a clone.

Prokaryotenkultur

In microbiology, the culture of prokaryotes ie the culture of bacteria ( Bacteria) and Archaea plays a significant role ( Archaea). The presented microbiological culture techniques can be applied to both domains, ie bacteria and archaea, apply, in practice, but more often working with bacterial cultures, as many belong to the archaea extremophiles, are so adapted to extreme habitats. In the Medical microbiology is the diagnostic bacterial culture of particular importance to detect pathogens to identify and to study their properties (eg, antibiotic sensitivity).

Culture of eukaryotic cells

In a cell culture refers to the cultivation of animal or plant cells - ie cells of eukaryotes - in a nutrient medium outside the organism.

Although it is also eukaryotic cells, the culture of yeasts and molds is carried out other than in animal or plant cells. They are among the subjects of study in microbiology and their cultures are similar to those of the bacteria, ie also they form colonies on solid media.

Viral culture

Viruses need a host cell suitable for their propagation, thus they can be propagated only in a culture of host cells. For viruses can therefore be used suitable eukaryotic cells, bacteriophages suitable bacterial cells.