Inoculation loop

An inoculating loop is a simple and frequently used tool in microbiology.

Installation and use

An inoculating loop is generally of a round, elongated handle to which a metal rod is attached and which is named after the German microbiologist Wilhelm Kolle Kolle as holder. There is a chuck in which a heat-resistant metal wire is clamped at its peak. The wire is bent at the end and forms a loop having a diameter of 1-5 mm. The inoculating loop is used primarily to create of a microorganism culture inoculum for a subculture to win ( " inoculate " ), or to single colonies by a Vereinzelungsausstrich.

Handling

The wire tip an inoculating loop will always be annealed before use. Here she is at an angle from above into the flame of a gas burner until the wire comes on bright red. Under these conditions, each biomolecule is completely oxidized. After annealing the wire tip is therefore sterile. Before the inoculum can be removed, the wire loop to cool down. In practice, this process is accelerated by several times in quick succession presses the eyelet onto the surface of the culture medium from which the inoculum is to be removed. As long as melts in the process of agar of the medium, the eye is much too hot.

After cooling, sweeps with the wire loop on the bacterial culture, or takes a single colony, and inoculating it on a different soil, or inoculating a liquid culture. It is also possible to withdraw an inoculum of a culture liquid by the sterile loop is immersed in the culture medium. Formed by the surface tension in the loop, a liquid film that contains enough cells. Finally, the inoculating loop is sterilized again by annealing and can be reused without contamination are to be feared.

Material variants

The metal wire is usually made of an alloy containing 80% platinum and 20% iridium; Eyelets from pure platinum are too soft. For cost reasons, wires of different composition can be used ( for example wire for electric heaters ). However, these have the disadvantage that, due to the heating of the metal surface oxides that may be toxic to microorganisms. In addition, such wires affect certain tests, is transferred to the culture material using the inoculating loop. This applies for example to the oxidase test, which is falsified by ferrous wires.

Except inoculating loops are used to inoculate also straight, not curved lugs to wires, so-called inoculation needles used. They are used to inoculate an agar culture medium in depth by inserting the loaded with microorganisms inoculating needle (Creating a " stab " ) and for the removal of inoculum from small colonies that are located close to other colonies.

Besides the described classical form of a pre-sterilized inoculating loop also Kunststoffimpfösen for single use are available.

As accessories for inoculating loops, there are simple stand, in which the holder will be provided with the inoculation loops.

Pictures

Schematic representation of a Vereinzelungsausstriches. Between the smears the inoculation loop, each annealed.

Using an inoculating loop scale Vereinzelungsausstrich. In the last smear include single colonies (clones ).