title: A consolidated analysis of the physiologic and molecular responses induced under acid stress in the legume-symbiont model-soil bacterium Sinorhizobium meliloti.
abstract: Abiotic stresses in general and extracellular acidity in particular disturb and limit nitrogen-fixing symbioses between rhizobia and their host legumes. Except for valuable molecular-biological studies on different rhizobia, no consolidated models have been formulated to describe the central physiologic changes that occur in acid-stressed bacteria. We present here an integrated analysis entailing the main cultural, metabolic, and molecular responses of the model bacterium Sinorhizobium meliloti growing under controlled acid stress in a chemostat. A stepwise extracellular acidification of the culture medium had indicated that S. meliloti stopped growing at ca. pH 6.0-6.1. Under such stress the rhizobia increased the O2 consumption per cell by more than 5-fold. This phenotype, together with an increase in the transcripts for several membrane cytochromes, entails a higher aerobic-respiration rate in the acid-stressed rhizobia. Multivariate analysis of global metabolome data served to unequivocally correlate specific-metabolite profiles with the extracellular pH, showing that at low pH the pentose-phosphate pathway exhibited increases in several transcripts, enzymes, and metabolites. Further analyses should be focused on the time course of the observed changes, its associated intracellular signaling, and on the comparison with the changes that operate during the sub lethal acid-adaptive response (ATR) in rhizobia.
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: W O
authors.initials: WO
authors.lastname: Draghi
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: M F
authors.initials: MF
authors.lastname: Del Papa
authors.affiliation: CeBiTec - Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Hellweg
authors.affiliation: CeBiTec - Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany.
authors.forename: S A
authors.initials: SA
authors.lastname: Watt
authors.affiliation: CeBiTec - Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany.
authors.forename: T F
authors.initials: TF
authors.lastname: Watt
authors.affiliation: CeBiTec - Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Barsch
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: M J
authors.initials: MJ
authors.lastname: Lozano
authors.affiliation: Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Lagares
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: M E
authors.initials: ME
authors.lastname: Salas
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: J L
authors.initials: JL
authors.lastname: López
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: F J
authors.initials: FJ
authors.lastname: Albicoro
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: J F
authors.initials: JF
authors.lastname: Nilsson
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: G A
authors.initials: GA
authors.lastname: Torres Tejerizo
authors.affiliation: CINDEFI - Centro de Investigación y Desarrollo en Fermentaciones Industriales, CONICET - Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: M F
authors.initials: MF
authors.lastname: Luna
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: M
authors.initials: M
authors.lastname: Pistorio
authors.affiliation: CINDEFI - Centro de Investigación y Desarrollo en Fermentaciones Industriales, CONICET - Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: J L
authors.initials: JL
authors.lastname: Boiardi
authors.affiliation: CeBiTec - Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Pühler
authors.affiliation: CeBiTec - Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Weidner
authors.affiliation: CeBiTec - Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Niehaus
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CONICET - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, calles 47 y 115, 1900-La Plata, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Lagares
mesh_terms: D000143:Acids / Q000378:metabolism; D003580:Cytochromes / Q000378:metabolism*; D007887:Fabaceae / Q000382:microbiology*; D006863:Hydrogen-Ion Concentration; D009586:Nitrogen Fixation; D010101:Oxygen Consumption; D010427:Pentose Phosphate Pathway; D012231:Rhizobium / Q000502:physiology*; D016962:Sinorhizobium meliloti / Q000502:physiology*; D012987:Soil; D013312:Stress, Physiological / Q000502:physiology*; D013559:Symbiosis
chemical_list: D000143:Acids; D003580:Cytochromes; D012987:Soil