FIG. 4.

(A) Map of the genomic region of the cbbR homolog in Synechococcus sp. strain PCC 7942. The filled bar represents the Synechococcus cbbR homolog. The triangle above the map indicates the MscI site where a 2.0-kbp gene cassette carrying the spectinomycin resistance gene (aad) was inserted to construct the MR4 mutant. Abbreviations for restriction endonuclease sites: H, HincII; M, MscI. (B) Southern blot analysis of DNA from the wild-type strain (WT; lanes 1 and 3) and the MR4 mutant (lanes 2 and 4) of Synechococcus sp. strain PCC 7942. DNA samples (5 μg per lane) were digested with HincII, fractionated on a 0.7% agarose gel, transferred to a positively charged nylon membrane (Hybond N+; Amersham), and hybridized with the ³²P-labeled gene-specific probes as indicated.