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. 2014 Feb 5;9(2):e81817. doi: 10.1371/journal.pone.0081817

Figure 1. Diagram of the auxotrophic strains, VCUSM20 and VCUSM21, construction.

Figure 1

The diagram is a schematic representation of mutation introduced at the rtx gene cluster on VCUSM14 (A) and VCUSM20 (B) chromosomes. It shows the double copies of Δctx operon, ΔhemA-hemM genes and rtxC::aphA genes in VCUSM20, and rtxC::aphA replaced with ΔrtxC/A in VCUSM21. Gene designations: ΔctxA operon, mutation in CT A subunit with complete deletion of accessory cholera enterotoxin (ace) and zonula occludens toxin (zot); repeat-in-toxin (rtx); bla, β-lactamase; sacB, Bacillus subtilis counterselectable marker sacB which encodes levan sucrase.