title: Pleiotropic physiological effects in the plant growth-promoting bacterium Azospirillum brasilense following chromosomal labeling in the clpX gene.
abstract: Azospirillum brasilense 8-I was chromosomally labeled with green fluorescent protein (gfp) genes, using either the native promoterless gfp gene or the mutant gfpmut2 gene under the transcriptional control of the neomycin phosphate transferase (npt2) promoter inserted into Tn5 suicide plasmid vectors. One A. brasilense exconjugant, showing a steady and strong fluorescence following irradiation with 365-nm UV light was characterized in detail. This strain, A. brasilense 8-I-gfp showed increased N(2)-fixation of approximately threefold, up to a twofold increase in exopolysaccharide production, and a significant decrease in indole-3-acetic acid and poly-beta-hydroxybutyrate production over the parental strain. Sequence analysis showed that the Tn5 carrying the gfp gene was inserted in the clpX gene encoding a heat-shock protein. This data is consistent with a model in which the observed physiological changes are a consequence of pleiotropic changes that occur as a consequence of impaired heat shock (stress) protein synthesis. In summary, (i) chromosomally labelled Azospirillum brasilense was obtained carrying either native or mutant gfp genes, (ii) Pleiotropic physiological effects were caused by disruption of the clpX gene as the consequence of the insertion, (iii) a new indole-3-acetic acid-attenuated mutant of A. brasilense producing only 0.25% of the indole-3-acetic acid produced by the wild-type is presented.
authors.affiliation: Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), Mar Bermejo 195, Col. Playa Palo de Santa Rita, La Paz, BCS 23090, Mexico.
authors.forename: Hilda
authors.initials: H
authors.lastname: Rodriguez
authors.forename: Alberto
authors.initials: A
authors.lastname: Mendoza
authors.forename: M Antonia
authors.initials: MA
authors.lastname: Cruz
authors.forename: Gina
authors.initials: G
authors.lastname: Holguin
authors.forename: Bernard R
authors.initials: BR
authors.lastname: Glick
authors.forename: Yoav
authors.initials: Y
authors.lastname: Bashan
mesh_terms: D000595:Amino Acid Sequence; D015806:Azospirillum brasilense / Q000235:genetics* / Q000378:metabolism*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D049071:Endopeptidase Clp / Q000235:genetics* / Q000502:physiology*; D005030:Ethylenes / Q000378:metabolism; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D006885:Hydroxybutyrates / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation; D011091:Polyesters / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013194:Staining and Labeling; D000094122:Polyhydroxybutyrates
chemical_list: D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D049071:Endopeptidase Clp; D005030:Ethylenes; D049452:Green Fluorescent Proteins; D006885:Hydroxybutyrates; D007210:Indoleacetic Acids; D009584:Nitrogen; D011091:Polyesters; D011135:Polysaccharides, Bacterial; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates; C030737:indoleacetic acid; C036216:ethylene