It is a method of determining bacterial motility.Instruments used specially in Microbiology

Microbiology

Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...

 are as follows:

Technique

A hollow tube with some culture medium is placed in semi-solid agar

Agar

Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...

 inside a bottle. Now 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 we find that:-

• the colonies of the non-motile bacteria remain confined within the tube at the site of inoculation
  Inoculation
  Inoculation is the placement of something that will grow or reproduce, and is most commonly used in respect of the introduction of a serum, vaccine, or antigenic substance into the body of a human or animal, especially to produce or boost immunity to a specific disease...
  
  
• the motile bacteria swim out from the bottom of the tube and colonize the surrounding medium as well

Confirmation may be obtained by subculture

Subculture (biology)

In Biology a subculture is a new cell or microbiological culture made by transferring some or all cells from a previous culture to fresh growth medium. This action is called subculturing or passaging the cells...

and retesting.