Comparative analysis of citrate fermentation gene locus. The 13-kb genomic region is present in K. pneumoniae MGH 78578 but absent in NTUH-K2044 (a). The location of the 13-kb genomic region for citrate fermentation, which includes two divergently transcribed operons, citS-oadGAB-citAB and citC2D2E2F2G2, are marked. The adjacent hypothetical orfs are shown in gray, among which the ltrA encodes a putative transcriptional regulator. The citYZ-citWX gene clusters downstream of the dapB in both MGH 78578 and NTUH-K2044 are also depicted. The G+C value for each orf in MGH 78578 is shown below each orf. The red bar indicates the corresponding location replaced by an apramycin resistant gene in the promoter knocked-out strain, NK8-Δcit, derived from the NK8 clinical strain. Corresponding citrate fermentation loci from S. enterica serovar Typhimurium LT2 and E. coli K12 are shown (b and c) with colours indicating homologous genes. Alternative gene names in parentheses on top of some orfs for better comparison were based on homology search. The locations of these regions in the genomes are marked below. In the LT2 genome, two clusters of citrate fermentation genes were found. The corresponding flanking genes for locus I, dcuC and rna, and locus II, rihC and dapB, are shown in black.