Polymorphism in the aerobactin-cloacin DF13 receptor genes from an enteroinvasive strain of Escherichia coli and pColV-K30 is associated only with a decrease in cloacin susceptibility.
We have cloned chromosomal genes mediating the aerobactin iron transport system from the enteroinvasive strain Escherichia coli 978-77. The physical map of the region spanning the siderophore biosynthesis genes and the upstream portion of the receptor gene in strain 978-77-derived clones was identical to the corresponding regions in pColV-K30, while the downstream portion was different. Recombinant plasmids derived from strain 978-77 encoded a 76-kDa outer membrane protein, in contrast to the 74-kDa polypeptide encoded by similar clones derived from pColV-K30. No differences were found in the uptake of ferric aerobactin mediated by either the 76-kDa- or the 74-kDa-encoding plasmids. In contrast, cells containing the 76-kDa-encoding plasmids showed a 16-fold decrease in susceptibility to cloacin compared with cells harboring the 74-kDa-encoding plasmids. Two classes of chimeric aerobactin receptor genes were constructed by exchanging sequences corresponding to the downstream portion from the aerobactin receptor gene of both systems. The pColV-K30-978-77 chimeric gene encoded a 76-kDa outer membrane protein which mediated a low level of cloacin susceptibility, whereas the 978-77-pColV-K30 type encoded a protein of 74 kDa determining a level of cloacin susceptibility identical to that mediated by pColV-K30.
Marolda
C L
CL
Department of Microbiology and Immunology, Oregon Health Sciences University, Portland 97201.
Valvano
M A
MA
Crosa
J H
JH
D001425:Bacterial Outer Membrane Proteins; D002874:Chromosome Mapping; D002989:Cloacin / Q000494:pharmacology*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D010957:Plasmids; D011110:Polymorphism, Genetic; D011971:Receptors, Immunologic / Q000235:genetics*; D011995:Recombination, Genetic
D001425:Bacterial Outer Membrane Proteins; D011971:Receptors, Immunologic; C034506:aerobactin receptor; D002989:Cloacin