A technique used to produce identical patterns of bacterial colonies on a series of petri plates. A petri plate containing bacterial colonies is inverted, and its surface is pressed against a cylindrical block covered with velveteen. In this way, 10 to 20% of the bacteria are transferred to the fabric. Subsequently, bacteria-free plates are inverted and pressed against the velveteen disc to pick up samples of the colonies. About eight replicas may be printed from a single pad in this way. If the medium contained in each of the secondary plates differs in its selective properties, then the hundreds of different bacterial clones transferred may be scored simultaneously for their responses to a given agent. See Chronology, 1952, Lederberg and Lederberg.
Subjects: Chemistry — Genetics and Genomics.