Vaccination loop
An inoculation loop is a simple tool that is often used in microbiology .
Structure and use
An inoculation loop usually consists of a round, elongated handle to which a metal rod is attached and which is called a collector holder after the German microbiologist Wilhelm Kolle . At its tip there is a chuck into which a heat-resistant metal wire is clamped. The end of the wire is bent over and forms an eyelet with a diameter of 1 to 5 mm. The inoculation loop is mainly used by a microorganism culture an inoculum to apply for a subculture ( inoculate ) or to individual colonies by a Vereinzelungsausstrich win.
handling
The wire tip of an inoculation loop is always annealed before use. Here it is held diagonally from above in the flame of a gas burner until the wire lights up bright red. Under these conditions every biomolecule is completely oxidized. After annealing, the wire tip is therefore sterile .
Before the inoculum can be removed, the wire loop must cool down. In practice, this process is accelerated by pressing the loop several times in quick succession on the surface of the culture medium from which the inoculum is to be removed. As long as the agar of the culture medium melts during this process , the loop is much too hot.
After cooling down, the wire loop is passed over the bacterial culture or a single colony is picked up and transferred to another culture medium or a liquid culture is inoculated . It is also possible to take an inoculum from a liquid culture by immersing the sterile loop in the culture medium. The surface tension creates a liquid film in the loop that contains enough cells.
Finally, the inoculation loop is re-sterilized by annealing and can be reused without fear of contamination.
Material, variants
The metal wire usually consists of an alloy that contains 80% platinum and 20% iridium ; Pure platinum eyelets are too soft. For reasons of cost, wires of a different composition can also be used (for example wire for electrical heating). However, these have the disadvantage that the heating creates oxides on the metal surface, which can have a toxic effect on microorganisms. Such wires also influence certain tests for which culture material is transferred using the inoculation loop. This applies, for example, to the oxidase test , which is falsified by wires containing iron.
In addition to inoculation loops, straight wires, so-called inoculation needles, are also used for inoculation. They are used to inoculate an agar culture medium in depth by piercing the inoculation needle loaded with microorganisms (creating a “piercing culture”) and to remove inoculum from small colonies that are close to other colonies.
In addition to the classic form of an inoculation loop described, pre-sterilized plastic inoculation loops for single use are also available.
As accessories for inoculation loops, there are simple stands in which the holders with the inoculation loops are placed.
See also
Web links
Individual evidence
- ↑ Entry on vaccination loop. In: Römpp Online . Georg Thieme Verlag, accessed on March 4, 2016.