Figure 2 Genomic variation at the citrate fermentation gene locus. Divergence of the 13-kb genomic region in 19 K. pneumoniae strains was detected by CGH analysis using the NimbleGen chips. Hybridization signals of each probes placed in the order of the
MGH 78578 genome were compared with those of the reference strain, NTUH-K2044. Ro-3306 in vitro The probes covering the cit genes and the oad genes of the 13-kb region were shown together with that of the adjacent orfs. The normalized CGH signals for each probe are plotted as black dots. The dot position above or under the baseline represents higher or lower copy of specific genomic sequence in comparison to the reference. The scores in vertical axis are log2 values of test/reference signal intensity Tucidinostat obtained from image scanning of hybridization results. The detection of elevated scores in the cit genes (citA-B, citS~citG2) in the last 10 strains (from NK3 to MGH 78278) is marked by solid triangles. Variations in the oad region are marked by open triangles. The oad genes within the 13-kb region are missing in NTUH-K2044, but the Selleck PND-1186 strain possesses an additional copy of oad genes at the tartrate-fermentation gene cluster
outside this region. In contrast, according to the genomic sequence, MGH 78578 (GenBank: CP000647) carries three copies of the oad genes, including one in the 13-kb region. This is also confirmed by the CGH result, which indicated that four strains, MGH 78578, NK8, CMKa05, and CMKa07, carry more than one copy of the oad genes and showed higher signal in the oad-probed region. On the other hand, CMKa10, NK5 and CG43, do not have oad genes and were represented by CGH plots below the baseline. We conclude that the 13-kb citrate fermentation gene sequence is not a uniform feature of K. pneumoniae and that the oadGAB gene copy number is variable among
the analyzed strains. In a recent report, it is shown that all K. pneumoniae strains could grow on citrate as sole carbon source when tested aerobically [17]. A stark contrast is the ability of K. pneumoniae to grown on citrate anaerobically. While all K. pneumoniae isolates mafosfamide can grow on citrate aerobically, our results suggested that only about half of them carry the 13-kb gene cluster for anaerobic citrate utilization. The 13-kb genomic island permits anaerobic growth in artificial urine As citrate is a major carbon source in human urine, we then asked whether the 13-kb genomic island could contribute to K. pneumoniae growth in the urinary tract. Although human urine is a suitable culture medium, the urine constituents can vary considerably between individuals under different conditions. It has been reported that the dissolved oxygen (DO) in urine is about 4.2 ppm, which is also variable and mainly reflects the renal metabolic state [18]. In patients with urinary infections, the urine DO is significantly reduced as a result of oxygen consumption by the microbes [18].