Iron-regulated salicylate synthesis by Pseudomonas spp.

Abstract

Two iron-regulated compounds have been found in acidified ethyl acetate extracts from culture supernatants of Pseudomonas aeruginosa and Pseudumonas cepucia type-strains. Synthesis of both compounds paralleled irondeficient growth, and was repressed in the presence of 100 p~-FeCl,. Yields of these substances varied among different strains and attained maximum levels during stationary phase. Thin layer chromatographic analysis in five different solvent systems revealed that the slower-moving compound chromatographed as two distinct bands, and showed R, values and spectral properties similar to pyochelin. The faster-moving compound co-migrated as a single band with a standard of commercial salicylic acid in each of the chromatographic systems tested. Moreover, a molecule with an identical R, was also produced by Pseudomonscs JIELorescens CHA401, which is known to synthesize salicylic acid as the only siderophore during iron-limited growth. Spectrophotometric and spectrofluorometric titrations led to the identification of this iron-regulated compound as salicylic acid, in agreement with the structure deduced from 'H-NMR and mass spectroscopy. The identity of the P. cepacia siderophore azurechelin as salicylic acid was also conclusively demonstrated. Salicylic acid, like pyochelin and pyoverdin, promoted P. aeruginosa growth in an iron-depleted medium. These results are consistent with a putative siderophore activity for salicylic acid, i.e. azurechelin, as has been demonstrated for P. ueruginossc, P. fluorescens and P. cepacia, Thus, salicylic acid is likely to act as a siderophore in more than one species belonging to the genus Pseudomonas.

The pobA gene of Burkholderia cenocepacia encodes a Group I Sfp-type phosphopantetheinyltransferase required for biosynthesis of the siderophores ornibactin and pyochelin

“…2(e). The absence of an orange zone around the growth of AHA27 on CAS plates confirms a previous observation that salicylate is not active as a siderophore in the CAS assay, although it has been proposed as a siderophore for B. cenocepacia (Sokol et al, 1992(Sokol et al, , 1999Visca et al, 1993).…”

“…A commonly employed mechanism for iron acquisition by bacteria is the secretion of lowmolecular-weight Fe(III)-binding compounds known as siderophores, which are then transported into the bacterium via specific outer membrane receptors (Braun, 2001;Crosa & Walsh, 2002). Most clinical isolates of B. cenocepacia produce the siderophores ornibactin and pyochelin (Sokol, 1986;Visca et al, 1993;Meyer et al, 1995;Darling et al, 1998;Thomas, 2007), and their production has been correlated with morbidity and mortality in CF patients and/or shown to contribute to pathology in animal models of respiratory infection (Sokol, 1986;Sokol & Woods, 1988;Sokol et al, 1999Sokol et al, , 2000Visser et al, 2004;Uehlinger et al, 2009). Ornibactin contains an L-ornithine-D-hydroxyaspartate-L-serine-L-ornithine backbone that requires two non-ribosomal peptide synthetases (NRPSs), OrbI and OrbJ, for its assembly (Stephan et al, 1993;Agnoli et al, 2006).…”

Salicylic Acid Produced by the Rhizobacterium Pseudomonas aeruginosa 7NSK2 Induces Resistance to Leaf Infection by Botrytis cinerea on Bean

“…For pseudomonads, antibiotics kanamycin, tetracycline, and carbenicillin were used at a concentration of 200 mg liter -1 . For iron-limited growth, King's medium B (KB) (16) and casamino acids broth (38) were used. In E. coli cultures, the antibiotics tetracycline and carbenicillin were used at 20 and 50 mg liter -1 , respectively.…”

Membrane-association determinants of the ω-amino acid monooxygenase PvdA, a pyoverdine biosynthetic enzyme from Pseudomonas aeruginosa

“…P. aeruginosa PAO1, or P. aeruginosa PAO1DpvdA cells expressing PvdA, D9PvdA, D9PvdA(G 15 AD) or D30PvdA, were grown to lateexponential phase at 37 uC in DCAA medium (Visca et al, 1993). When necessary, the medium was supplemented with 150 mg carbenicillin ml 21 .…”