FIG. 4.

HP0190 is an essential gene. (A) Genomic region surrounding HP0190. Gene annotation is according to Tomb et al. (47). Numbers above each open reading frame indicate the number of transposon insertions detected by MATT. (B) A knockout cassette can integrate at either locus containing HP0190 in a strain containing a second copy at the rdxA locus. The number above each lane indicates independent chloramphenicol-resistant clones. The letters represent the primer pair used for amplification. A lanes (e.g. 1A, 2A, etc.) depict PCR results with primers rdx1 and cat2, which will only give a product if integration occurred at the rdxA locus. B lanes indicate PCR with primers HP0190-1 and cat2, which give a product for integration at the native locus and the rdxA locus. Reactions were fractionated on a 0.8% agarose gel, and DNA was visualized by ethidium bromide staining. The far left lane contains a 1-kb ladder DNA standard (Gibco-BRL). Clones 1, 2, and 5 have integrated the knockout cassette into the gene copy at the rdxA locus. Clones 3 and 4 have integrated the knockout cassette into the gene copy at the native HP0190 locus.