Cragie tube
The Cragie tube or Craigie tube is a method used in microbiology for determining bacterial motility.
Technique
A hollow tube with some culture medium is placed in semi-solid agar inside a bottle. A sample of the bacterium to be tested is inoculated into the medium in the hollow tube and the setup is incubated at 37 °C overnight.Observation
On examining the areas where bacterial growth has occurred there are several observations to be made:- the colonies of the non-motile bacteria remain confined within the tube at the site of inoculation
- the motile bacteria swim out from the bottom of the tube and colonize the surrounding medium as well