Botany · Ch 4 — Principles and Processes of Biotechnology
Replica plating technique
Replica plating technique
Replica plating solves a different, practical problem: how do you test many different colonies against many different conditions (say, several different antibiotics, or the presence/absence of a growth factor) without physically picking up and re-streaking every single colony by hand? The technique works by pressing a sterile fabric or filter pad against an existing 'master' culture plate, which picks up a faithful imprint of every colony's exact position, and then pressing that same pad onto one or more fresh plates, each carrying a different selective medium. Because the imprint preserves the colonies' original relative positions, a colony that grows at a given spot on the fresh, antibiotic-free plate but fails to grow at the same spot on the original antibiotic-containing plate can be immediately identified as antibiotic-sensitive, purely by comparing the two plates side by side - al …
What this figure shows. A four-stage flow diagram: a master plate (containing ampicillin) with a full lawn of colonies has a sterile velvet pad pressed onto a block placed over it, picking up imprints of all the colonies; the pad is then pressed onto and replicated onto a second, fresh plate that lacks ampicillin; after incubation, the fresh plate shows growth of ampicillin-sensitive colonies at the same relative positions as on the master, letting …