Streak plate method is a pure culture technique which helps in isolating desired colonies

from contaminants. The procedure begins by sterilizing a wire

loop in flame. Cool the sterilized loop by allowing it to

stand for a few seconds. Dip the loop into a sample containing a mixture

of bacteria. Depending on the sample, the loop may pick up hundreds or thousands of

bacteria, which are spread back and forth across the surface of the agar.

Make a uniform smear with the inoculum at the edge of the plate.

Sterilise the loop as mentioned above, and make streaks from the smear.

Since there is thinning of inoculum during streaking, isolated colonies are formed at

ideal streak point where the spreading has separated the individual (or group) of cells

at locations where they can form individual colonies

The pattern of streaking varies with different type of streak plate techniques, for e.g.

Quadrant streak, T-streak etc. During the incubation, the bacteria multiply

and produce colonies. Intermittent flaming of the loop can be done

during streaking to reduce the load of the organism so that there is a better chance

of getting isolated colonies. Keep the plate covered as much as possible

to avoid contamination While streaking a section of the plate, try

to keep the inoculating loop in contact with the surface of the agar at all times.