Colicin expression Another group of genes upregulated in iron-def

Colicin expression Another group of genes upregulated in iron-deficient conditions were the genes encoding the Microcin V (cvaA

cvaB cvaC) and Colicin Ia, which were also upregulated in human serum and urine. Previous reports have shown the influence of bacterial intracellular iron levels on colicin expression, but the reason of such induction is still poorly understood [29–31]. Of note, transcription of immunity protein for both colicins was not upregulated in any of the conditions studied except for Colicin Ia in human serum. Expression of ORFs of unknown function in iron-deficient environments Two ORFs with unknown functions, shiF and ORF 123, were upregulated in iron-deficient BMS202 order conditions, with large fold changes in vivo and ex vivo. ORF 123 was the most strongly upregulated (> 100-fold) in the 3 test conditions, and was expressed 3 to 4 times more strongly than the iron acquisition systems. A nucleotide homology search using the BLAST program [32]

showed that ORF 123 is highly homologous (99%) to an ORF present in E. coli plasmids possessing a CVP region (such pAPEC-O1-ColI-BM, pAPEC-O2-ColV and pAPEC-1) or located on the chromosome of UPEC strains such as CFT073 (ORF c1220; 94%) and 536 (ORF ECP–0281; 95%). No homologous gene is find more found in the commensal E. coli strain MG1655. Transcriptome analysis by Mobley et al.[16]

showed over-expression of c1220 transcripts in E. coli CFT073 in a mouse model of UTI. The putative protein encoded by ORF Lck 123 showed 45-50% identity to three phospho-2-dehydro-3-deoxyheptonate aldolases that catalyze the first reaction of the shikimate pathway and are present on the chromosome of E. coli K12. This pathway involves seven enzymatic reactions that generate chorismate, a factor involved in the synthesis of three aromatic amino acids (tyrosine, tryptophan and phenylalanine) [33]. However, this pathway is also involved in other reactions, such as biosynthesis of siderophore group nonribosomal peptides such as yersiniabactin and enterobactin. In plasmid pS88, as in other CVP-containing plasmids, ORF 123 lies just upstream of iroN and is preceded by a sequence resembling the Fur Box consensus sequence (5′-GATAATGATAATCATTATC) [34, 35]. BLAST analysis of complete genomes available on publicly available database showed that ORF 123 is only found when the salmochelin operon is present but the reciprocity is not true, as for example in strain UTI89, which harbors only an iro locus. On the chromosome of E. coli strains CFT073 and 536, this ORF (c1220 and ECP_0281, respectively) is located in a pathogenicity island containing an iro locus but is 20–30 kb distant from the iro locus.

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