Identification of a new iron regulated locus of Salmonella typhi.
In order to identify genes belonging to the Fur regulon of Salmonella typhi which are absent from Escherichia coli K-12, a plasmid gene bank consisting of 4000 independent clones was screened for Fur regulated promoters using the Fur titration assay (FURTA). DNA probes generated from FURTA positive plasmids were then used for hybridization with chromosomal DNA from S. typhi, Salmonella typhimurium and E. coli. Using these techniques we identified an iron regulated locus present in S. typhi and S. typhimurium but not in E. coli. Further cloning and nucleotide sequence analysis identified two open reading frames, termed iroBC, organized in a typical operon structure. The genes iroBC were located at 4 and 57 centisomes on the physical maps of Salmonella typhi and S. typhimurium, respectively. This region of the S. typhimurium chromosome contains a large DNA loop which is absent from the corresponding area of the E. coli chromosome. Finally, we developed a new method for generation of single copy transcriptional fusions. A suicide vector was constructed, which allows for the generation of chromosomal fusions to the promoterless E. coli lacZYA genes. By integration of this construct at the iro locus we could establish iron responsive expression of iroBC.
Bäumler
A J
AJ
Department of Molecular Microbiology and Immunology, Oregon Health Sciences University, Portland 97201-3098, USA.
Tsolis
R M
RM
van der Velden
A W
AW
Stojiljkovic
I
I
Anic
S
S
Heffron
F
F
D001426:Bacterial Proteins / Q000235:genetics; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis; D004274:DNA, Recombinant; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005798:Genes, Bacterial; D017930:Genes, Reporter / Q000235:genetics; D005822:Genetic Vectors / Q000235:genetics; D007501:Iron / Q000494:pharmacology*; D007763:Lac Operon; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D018085:Regulon / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D015183:Restriction Mapping; D012485:Salmonella typhi / Q000235:genetics*; D012486:Salmonella typhimurium / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004274:DNA, Recombinant; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D007501:Iron