A culture of bacteiral cells are spread on a petri plate of complete medium. Both prototrophs and auxotrophs grow on the medium and their colonies appear in a random arrangement. Piece of sterilized velvet is pressed on this plate of colonies, and the velvet pickus up some cells form each colony. The velvet can then be pressed on a number of petri plates, whcih reproduces the same pattern of bacterial colonies. One of these replica plates contains minimal media, and each of the remaining replica plates contain minimal medium supplemented with a different compound. A cplony that grows on minimal media represents a protoroph, whereas a colony tha fails to grow on minimal medium represents an auxotroph.REPLICA PLATING CONTINUEDAn autotroph that grows on a supplemented minimal medium plate is unable to synthesize either the supplemented compound or a precursor to that compound. the indiviulal clonies of interest can then be isolated and grown out.
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