Siderophore-mediated iron uptake in Alcaligenes eutrophus CH34 and identification of aleB encoding the ferric iron-alcaligin E receptor.
Siderophore production in response to iron limitation was observed in Alcaligenes eutrophus CH34, and the corresponding siderophore was named alcaligin E. Alcaligin E was characterized as a phenolate-type siderophore containing neither catecholate nor hydroxamate groups. Alcaligin E promoted the growth of siderophore-deficient A. eutrophus mutants under iron-restricted conditions and promoted 59Fe uptake by iron-limited cells. However, the growth of the Sid- mutant AE1152, which was obtained from CH34 by Tn5-Tc mutagenesis, was completely inhibited by the addition of alcaligin E. AE1152 also showed strongly reduced 59Fe uptake in the presence of alcaligin E. This indicates that a gene, designated aleB, which is involved in transport of ferric iron-alcaligin E across the membrane is inactivated. The aleB gene was cloned, and its putative amino acid sequence showed strong similarity to those of ferric iron-siderophore receptor proteins. Both wild-type strain CH34 and aleB mutant AE1152 were able to use the same heterologous siderophores, indicating that AleB is involved only in ferric iron-alcaligin E uptake. Interestingly, no utilization of pyochelin, which is also a phenolate-type siderophore, was observed for A. eutrophus CH34. Genetic studies of different Sid- mutants, obtained after transposon mutagenesis, showed that the genes involved in alcaligin E and ferric iron-alcaligin E receptor biosynthesis are clustered in a 20-kb region on the A. eutrophus CH34 chromosome in the proximity of the cys-232 locus.
Gilis
A
A
Milieutechnologie, Vlaamse Instelling voor Technologisch Onderzoek, Mol, Belgium.
Khan
M A
MA
Cornelis
P
P
Meyer
J M
JM
Mergeay
M
M
van der Lelie
D
D
D000421:Alcaligenes / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001692:Biological Transport; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D005290:Ferric Compounds / Q000378:metabolism*; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006877:Hydroxamic Acids; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D010636:Phenols; D011956:Receptors, Cell Surface / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D017262:Siderophores / Q000145:classification / Q000378:metabolism*
D001426:Bacterial Proteins; D005290:Ferric Compounds; D006877:Hydroxamic Acids; D010636:Phenols; D011956:Receptors, Cell Surface; D017262:Siderophores; C092056:alcaligin; C101643:ferric iron-alcaligin E receptor, Ralstonia eutropha; C101642:alcaligin E; D007501:Iron