title: Different and new Nod factors produced by Rhizobium tropici CIAT899 following Na+ stress.
abstract: The root nodule bacterium Rhizobium tropici strain CIAT899 is highly stress resistant. It grows under acid conditions, in large amounts of salt, and at high osmotic pressure. An earlier study reported a substantial qualitative and quantitative effect of acid stress on the biosynthesis of Nod factors. The aim of the present work was to investigate the effect of high salt (NaCl) concentrations, another common stress factor, on Nod factor production. For this purpose, thin-layer chromatography, HPLC and MS analyses were carried out. The expression of nodulation genes was also studied using a nodP:lacZ fusion. High concentrations of sodium enhanced nod gene expression and Nod factor biosynthesis. The effect is sodium specific because high potassium or chloride concentrations did not have this effect. Under salt stress conditions, 46 different Nod factors were identified in a CIAT899 culture, compared with 29 different Nod factors under control conditions. Only 15 Nod factor structures were common to both conditions. Under salt stress conditions, 14 different new Nod factor structures were identified that were not observed as being produced under neutral or acid conditions. The implications of our results are that stress has a great influence on Nod factor biosynthesis and that new, very interesting regulatory mechanisms, worth investigating, are involved in controlling Nod factor biosynthesis.
authors.affiliation: Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Sevilla, Profesor García González, Sevilla, España.
authors.forename: Jana
authors.initials: J
authors.lastname: Estévez
authors.forename: María Eugenia
authors.initials: ME
authors.lastname: Soria-Díaz
authors.forename: Francisco Fernández
authors.initials: FF
authors.lastname: de Córdoba
authors.forename: Belén
authors.initials: B
authors.lastname: Morón
authors.forename: Hamid
authors.initials: H
authors.lastname: Manyani
authors.forename: Antonio
authors.initials: A
authors.lastname: Gil
authors.forename: Jane
authors.initials: J
authors.lastname: Thomas-Oates
authors.forename: Antonius Albertus Nicolaas
authors.initials: AA
authors.lastname: van Brussel
authors.forename: Marta Susana
authors.initials: MS
authors.lastname: Dardanelli
authors.forename: Carolina
authors.initials: C
authors.lastname: Sousa
authors.forename: Manuel
authors.initials: M
authors.lastname: Megías
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D019677:Artificial Gene Fusion; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D020869:Gene Expression Profiling; D017930:Genes, Reporter; D008070:Lipopolysaccharides / Q000096:biosynthesis*; D013058:Mass Spectrometry; D009997:Osmotic Pressure; D042162:Rhizobium tropici / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D008070:Lipopolysaccharides; D012965:Sodium Chloride; D001616:beta-Galactosidase