A modified device for replica plating

Replica plating, described 26 years ago by Lederberg and Lederberg (1952), is a standard technique for the selection of bacterial mutants. The principal difficulty with this technique is smudging and loss of colonial identity, which occurs as the velveteen collects moisture from the agar surface. Although predrying the plates and increasing the concentration of agar in the medium decreases this problem to some extent, it is difficult to entirely eliminate smudging. As a result of the difficulties encountered with velveteen, the authors attempted to find a fabric that would be suitable for replica plating but would not become saturated with moisture during the procedure. By replacing velveteen with the 'hook-half' of Velcro (Velcro USA, Inc, Manchester, New Hampshire), we have been able to eliminate smudging.