Identification of an additional ferric-siderophore uptake gene clustered with receptor, biosynthesis, and fur-like regulatory genes in fluorescent Pseudomonas sp. strain M114.
Five cosmid clones with insert sizes averaging 22.6 kilobases (kb) were isolated after complementation of 22 Tn5-induced Sid- mutants of Pseudomonas sp. strain M114. One of these plasmids (pMS639) was also shown to encode ferric-siderophore receptor and dissociation functions. The receptor gene was located on this plasmid since introduction of the plasmid into three wild-type fluorescent pseudomonads enabled them to utilize the ferric-siderophore from strain M114. The presence of an extra iron-regulated protein in the outer membrane profile of one of these strains was detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A ferric-siderophore dissociation gene was attributed to pMS639 since it complemented the ferric-siderophore uptake mutation in strain M114FR2. This mutant was not defective in the outer membrane receptor for ferric-siderophore but apparently accumulated ferric-siderophore internally. Since ferric-citrate alleviated the iron stress of the mutant, there was no defect in iron metabolism subsequent to release of iron from the ferric-siderophore complex. Consequently, this mutant was defective in ferric-siderophore dissociation. A fur-like regulatory gene also present on pMS639 was subcloned to a 7.0-kb BglII insert of pCUP5 and was located approximately 7.3 kb from the receptor region. These results established that the 27.2-kb insert of pMS639 encoded at least two siderophore biosynthesis genes, ferric-siderophore receptor and dissociation genes, and a fur-like regulatory gene from the biocontrol fluorescent Pseudomonas sp. strain M114.
O'Sullivan
D J
DJ
Microbiology Department, University College, Cork, Ireland.
Morris
J
J
O'Gara
F
F
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001693:Biological Transport, Active / Q000235:genetics; D003001:Cloning, Molecular; D005453:Fluorescence; D005798:Genes, Bacterial; D005809:Genes, Regulator; D005816:Genetic Complementation Test; D007502:Iron Chelating Agents / Q000378:metabolism / Q000493:pharmacokinetics*; D010957:Plasmids; D011549:Pseudomonas / Q000235:genetics / Q000378:metabolism*; D017262:Siderophores
D001425:Bacterial Outer Membrane Proteins; D007502:Iron Chelating Agents; D017262:Siderophores