Bacterial Plating Out Technique Experiment (streak plate method) Virtual Lab

Theoretical Background/Context

• In microbiology, streaking is a technique used to isolate a pure strain from a single species of microorganism, often bacteria.
• The dilution or isolation by streaking method was first developed by Loeffler and Gaffky in Koch’s laboratory, which involves the dilution of bacteria by systematically streaking them over the exterior of the agar in a Petri dish to obtain isolated colonies which will then grow into the number of cells or isolated colonies.
• Streaking is rapid and ideally a simple process of isolation dilution.
• The technique is done by diluting a comparatively large concentration of bacteria to a smaller concentration.
• The decrease of bacteria should show that colonies are sufficiently spread apart to effect the separation of the different types of microbes.
• Streaking is done using a sterile tool, such as a cotton swab or commonly an inoculation loop.
• Aseptic techniques are used to maintain microbiological cultures and to prevent contamination of the growth medium.
   

Principle of Work

The streak plate method is a rapid qualitative isolation method.
It is essentially a dilution technique that involves spreading a loopful of culture over the surface of an agar plate.
The resulting diminution of the population size ensures that, following inoculation, individual cells will be sufficiently far apart on the surface of the agar medium to effect a separation of the different species present.
The streaking process will dilute out the sample that was placed in the initial region of the agar surface.