Table 5.
Putative Fur boxes identified in Cronobacter iron acquisition systems and fold increase in expression under iron-depleted conditions
| Gene or operon(s) | Putative phenotype | Sequence (5′–3′)a | No. of identical bases | Locationb | Fold increase in expressionc |
|---|---|---|---|---|---|
| iucABCD-iutA | Cronobactin biosynthesis and transport | CATAACGATAATCATTATC | 17 | 19 bp of iucA | 4.1 ± 0.2 (iucC), 2.9 ± 0.1 (iutA) |
| shiF-viuB | Ferric reductase and MFS permease | AATATTTGTTTTCATTAAT | 11 | 44 bp of shiF | 2.2 ± 0.2 (viuB) |
| fepA-entD-fes-ybdZ-entF | Enterobactin biosynthesis, receptor and iron release | GATAATAACTATCATTATC | 17 | 18 bp of fepA, 71 bp of fes | 1.5 ± 0.05 (fepA), 4.4 ± 0.3 (entF) |
| fepE | Enterobactin transport | Not present | 0.8 ± 0.03 (fepE) | ||
| entCEBAH-fepB | Enterobactin transport and biosynthesis | GAAAATGAGAAGCATTATT ACAAATGATAACAATTATC | 16, 14 | 26 bp of fepB, 29 bp of entC | 1.5 ± 0.08 (fepB), 1.7 ± 0.3 (entC) |
| entS-fepDGC | Enterobactin transport and biosynthesis | GATAATAACTATCATTATC | 16 | 19 bp of fepD, 107 bp of entS | No expression (fepG), 1.0 ± 0.04 (entS) |
| fhuACDB | Ferrichrome receptor and hydroxamate transport | GCGCATAATAATAATTCTC | 13 | 42 bp of fhuA | 1.8 ± 0.2 (fhuA) |
| fecIRABCDE | Ferric dicitrate receptor and transport | TGTAATGATAACCATTCTC | 16 | 45 bp of fecI | 3.4 ± 0.2 (fecB)d |
| eitABC-eitD | ABC ferric transporter | AAGAATGATTTTCATTTGC | 13 | 75 bp of eitA, 141 bp of eitD | 0.7 ± 0.05 (eitA), no expression (eitD) |
| feoABC | Ferrous transporter | AAAAACCATTCTCATTACC | 12 | 103 bp of feoA | 1.8 ± 0.3 (feoB) |
| efeUOB | Ferrous transporter | GGTAATGATAATCACTTTC | 16 | 59 bp of efeU | 1.9 ± 0.3 (efeO) |
| yncD | Siderophore receptor | GAGAATAATAATCATTATT | 16 | 164 bp of yncD | 3.4 ± 0.4 (yncD) |
| foxA | Ferroxamine receptor | GATAATAATTCGCATTCTT | 13 | 60 bp of foxA | 3.0 ± 0.4 (foxA) |
| fhuE | Ferric rhodotorulic acid/coprogen receptor | ACAAATGATTATATTTCTC | 12 | 138 bp of fhuE | 2.7 ± 0.3 (fhuE) |
| pfeA | Ferric enterobactin receptor | GATAATTATTATCATTATC | 17 | 47 bp of pfeA | 4.3 ± 0.4 (pfeA) |
| fcuA | Hydroxamate receptor | AATAATGACAGGACAACCT | 8 | 6 bp of fcuA | 2.8 ± 0.3 (fcuA) |
| GCAAATGATTATTAGTAAC | 14 | 116 bp of yncE | |||
| fct | Ferrichrysobactin receptor | GGTAATGATTTTCAATATC | 16 | 63 bp of fct, 189 bp of fesA | 2.8 ± 0.2 (fct) |
| fhuF | Ferric reductase | AGGATTGGCAATCATTATC | 13 | 28 bp of fhuF | 2.1 ± 0.4 (fhuF) |
| btuB | Vitamin B12/cobalamin receptor | Not present | 1.0 ± 0.04 (btuB) | ||
| yfeX | Heme iron extractor | Not present | 0.76 ± 0.2 (yfeX) |
a
Comparison with E. coli consensus 5′-GATAATGATAATCATTATC-3′ (17). Identical nucleotides are in boldface type.
b
Number of nucleotides upstream of the start codon.
c
Average ± standard deviation of three RT-PCRs to determine fold change in the expression of the gene under iron-depleted conditions (LB broth supplemented with 300 μM DIP). All RT-PCRs were performed in C. turicensis z3032, except for those for fhuA, fct, and fcuA as well as fecB, which were performed in C. dublinensis LMG23825 and C. sakazakii 2151, respectively.
d
Growth in LB broth supplemented with 300 μM DIP and 1 mM citrate.