FIG. 2.

Schematic representation of the targeting strategy for generating a mutS ndk double-knockout mutant. The ndk-coding region in the mutS single-knockout mutant was replaced by a kanamycin resistance-encoding cassette through reciprocal recombination to generate a mutS ndk double-knockout mutant. White boxes represent coding regions of mutS and ndk. Light gray boxes represent the spectinomycin resistance-encoding cassette. Dark gray boxes represent the kanamycin resistance-encoding cassette.