TargeTron Vectors are offered for use with the TargeTron Gene Knockout System (Sigma-Aldrich, St. Louis, MO). The vectors enhance the capabilities and increase the flexibility of the system, providing with an efficient method for knock out of multiple genes in prokaryotic organisms, to generate knockouts without using selection or by using removable selection, and to use the system to produce knockouts in organisms lacking a source of T7 RNA polymerase. The vector pACD4K-C-loxP is a linearized E. coli expression vector containing loxP sites to facilitate the removal of the kanamycin marker. This enables the generation of multiple, site-specific knockouts in the same bacterial chromosome. The pACD4 TargeTron Vector Set (no selectable marker) contains four linearized vectors lacking the kanamycin RAM marker. Additionally, each vector has an A, C, G, or T in the delta + 1 position. This facilitates proper base pairing of the group II intron RNA for different target site designs resulting in efficient precursor RNA splicing to form active TargeTron RNP's. The pACD4 TargeTron Vector Set allows researchers to generate prokaryotic knockouts when selection cannot be used. The introduction of the pAR1219 TargeTron Vector provides a source of T7 RNA polymerase when co-transformed with TargeTron Vector pACD4K-C, included in the TargeTron Gene Knockout System (TA0100). Adding an external source of T7 RNA polymerase allows for the creation of knockouts in organisms such as Salmonella typhimurium and Shigella flexneri as well as in non-DE3 strains of E. coli. Sigma-Aldrich 800-325-3010 www.sigma-aldrich.com