Diagram of the genome region of D. vulgaris containing the predicted six-gene operon apsBA-qmoABC-DVU0851. The locations of the probe used for Northern blot analyses (A), amplified regions from D. vulgaris genomic DNA and cDNA (B to D), deleted segments (E and F), and template regions for probes for Southern confirmation of deletions (G and H) are shown. Arrows represent ORFs, and arrowheads indicate the direction of transcription. Genes in gray are predicted to be in neighboring operons. COG, clusters of orthologous genes.