Last Updated on February 20, 2020 by Sagar Aryal

Aseptic techniques are used to maintain microbiological cultures and to prevent contamination of the growth medium.

Streaking is done using a sterile tool, such as a cotton swab or commonly an inoculation loop.

The decrease of bacteria should show that colonies are sufficiently spread apart to effect the separation of the different types of microbes.

The technique is done by diluting a comparatively large concentration of bacteria to a smaller concentration.

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.

In microbiology, streaking is a technique used to isolate a pure strain from a single species of microorganism, often bacteria.

The streak plate method is a rapid qualitative isolation method.

The techniques commonly used for isolation of discrete colonies initially require that the number of organisms in the inoculums be reduced.

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.

In the streaking procedure, a sterile loop or swab is used to obtain an uncontaminated microbial culture. The process is called “picking colonies” when it is done from an agar plate with isolated colonies and is transferred to a new agar or gelatin plate using a sterile loop or needle.

The inoculating loop or needle is then streaked over an agar surface.

On the initial region of the streak, many microorganisms are deposited resulting in confluent growth or the growth of culture over the entire surface of the streaked area.

The loop is sterilized by heating the loop in the blue flame of the Bunsen burner, between streaking different sections, or zones and thus lesser microorganisms are deposited as the streaking progresses.