Replica plating
Replica plating is a microbiology method used to copy the pattern of colonies from a primary plate onto several secondary plates that have different growth conditions, such as lacking nutrients or containing antibiotics. A velveteen-covered stamp is pressed onto the master plate to pick up colonies, then stamped onto the other plates so each secondary plate has the same colony layout as the original. This lets scientists compare plates and quickly look for changes in how the colonies grow.
Typically, 30–300 colonies are replicated, since stamping each one individually is hard. By comparing the master plate with the secondary plates, researchers can screen for various traits, such as auxotrophy (nutritional requirements) or antibiotic resistance. The technique is especially useful for negative screening: if a colony appears on the master plate but not on a selective plate, it is sensitive to the substance on that plate. A final nonselective plate is often added to confirm that the transfer worked and that the lack of growth on the selective plate is due to the growth condition, not a transfer error.
A common example is using an Ampicillin-containing plate. Colonies that are sensitive to ampicillin will disappear on the Amp+ plate but remain visible on the master plate, allowing researchers to identify them. If growth is seen on the nonselective plate but not on the selective plate, the absence on the selective plate is due to the selective agent.
By using many different secondary plates, replica plating lets researchers quickly screen thousands of colonies for many phenotypes. The method was described in 1952 by Esther and Joshua Lederberg. They chose cotton velveteen as the stamp material because it reliably transfers colonies without distorting patterns, unlike paper, and it was cheaper and more practical than nylon velvet. Although first demonstrated with bacteria, replica plating is also used with yeast and other organisms.
This page was last edited on 3 February 2026, at 05:58 (CET).