Why are there two independent mutants for each gene within the Keio collection?
The Keio collection is comprised of 3985 deletions in duplicate (7970 total) of E. coli K-12 strain BW25113 (Datsenko and Wanner, 2000), a strain with a well-defined pedigree that has not been subjected to mutagens. Mutants were directly selected as kanamycin-resistant (KmR) colonies after electroporation of BW25113 carrying the ? Red expression plasmid pKD46 (Datsenko and Wanner, 2000). To alleviate problems that can arise in high-throughput experiments, resulting from handling errors, crosscontamination, and accumulation of secondary mutations, two independent mutants were saved for each deletion. Per publication: http: //www. pubmedcentral. nih. gov/articlerender. fcgi?artid=1681482