Streaking (microbiology)

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

Samples can then be taken from the resulting colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested.

The modern streak plate method has progressed from the efforts of Robert Koch and other microbiologists to obtain microbiological cultures of bacteria in order to study them.

The dilution or isolation by streaking method was first developed in Koch's laboratory by his two assistants Friedrick Loeffler and Georg Theodor August Gaffky.

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

The inoculation loop is then dragged across the surface of the agar back and forth in a zigzag motion until approximately 30% of the plate has been covered.

From these mixed colonies, single bacterial or fungal species can be identified based on their morphological (size/shape/colour) differences, and then sub-cultured to a new media plate to yield a pure culture for further analysis.

Bacteria exist in water, soil and food, on skin, and intestinal tract normal flora.

The human body has billions of bacteria which creates the normal flora fighting against the invading pathogens.