Identification of an additional ferric-siderophore uptake gene clustered with receptor, biosynthesis, and fur-like regulatory genes in fluorescent Pseudomonas sp. strain M114

Abstract

Five cosmid clones with insert sizes averaging 22.6 kilobases (kb) were isolated after complementation of 22 TnS-induced Sidmutants 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 proffle 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 BgllI insert of pCUP5 and was located-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 afur-like regulatory gene from the biocontrol fluorescent Pseudomonas sp. strain M114.

The ferripyoverdine receptor FpvA of Pseudomonas aeruginosa PAO1 recognizes the ferripyoverdines of P. aeruginosa PAO1 and P. fluorescens ATCC 13525

“…The site of recognition likely involves the peptide part of the pyoverdine molecule, which varies greatly from one pyoverdine to another, by the number and nature of the amino acids [1,5]. Speci¢city of iron uptake is typically so restricted that it has permitted the use of the ferripyoverdine receptor as a powerful marker for monitoring bacterial release in natural environments [6], or the cloning of various ferripyoverdine receptor genes [2,3,7]. Exceptions have, however, been described, with some strains able to incorporate iron via pyoverdines originating from other strains [4,8,9,11].…”

Escherichia coli ferric uptake regulator (Fur) can mediate regulation of a pseudomonad iron-regulated promoter

“…1. The origin of pMS639 has been described [5,9]. Bacterial strains were cultured and antibiotics added where required as described previously [7].…”

Characterization of Fluorescent Siderophore-Mediated Iron Uptake in Pseudomonas sp. Strain M114: Evidence for the Existence of an Additional Ferric Siderophore Receptor

“…The siderophores usually consist of a fluorescent chromophore linked to a peptide chain and differ mainly in the size and composition of the peptide chain (6,25,30,31). The uptake of these complexes has been shown to be mediated by specific receptors in the outer membrane (14,16,22). The production of both biosynthetic (17,19) and uptake (9, 14, 23) proteins is stringently regulated by iron.…”

“…strain M114 that the ferric siderophore complex (ferric pseudobactin * Corresponding author. M114) is transported across the membrane into the cytosol before the release of iron (22). However, very little is known about how the complex crosses the cell envelope.…”

“…strain M114; these proteins are not present in conditions of excess iron (23). One of these proteins (89 kDa) is required for the transport of ferric pseudobactin M114 (22). In this paper we report the construction and characterization of a mutant of strain M114 lacking this ferric siderophore receptor.…”