title: Metabolic engineering of ammonium release for nitrogen-fixing multispecies microbial cell-factories.
abstract: The biological nitrogen fixation carried out by some Bacteria and Archaea is one of the most attractive alternatives to synthetic nitrogen fertilizers. In this study we compared the effect of controlling the maximum activation state of the Azotobacter vinelandii glutamine synthase by a point mutation at the active site (D49S mutation) and impairing the ammonium-dependent homeostatic control of nitrogen-fixation genes expression by the ΔnifL mutation on ammonium release by the cells. Strains bearing the single D49S mutation were more efficient ammonium producers under carbon/energy limiting conditions and sustained microalgae growth at the expense of atmospheric N2 in synthetic microalgae-bacteria consortia. Ammonium delivery by the different strains had implications for the microalga׳s cell-size distribution. It was uncovered an extensive cross regulation between nitrogen fixation and assimilation that extends current knowledge on this key metabolic pathway and might represent valuable hints for further improvements of versatile N2-fixing microbial-cell factories.
authors.affiliation: Instituto de Investigaciones en Biodiversidad y Biotecnología - Consejo Nacional de Investigaciones Científicas y Técnicas, Mar del Plata, Buenos Aires, Argentina; Fundación para Investigaciones Biológicas Aplicadas, Argentina.
authors.forename: Juan Cesar Federico
authors.initials: JC
authors.lastname: Ortiz-Marquez
authors.affiliation: Instituto de Investigaciones en Biodiversidad y Biotecnología - Consejo Nacional de Investigaciones Científicas y Técnicas, Mar del Plata, Buenos Aires, Argentina; Fundación para Investigaciones Biológicas Aplicadas, Argentina.
authors.forename: Mauro
authors.initials: M
authors.lastname: Do Nascimento
authors.affiliation: Instituto de Investigaciones en Biodiversidad y Biotecnología - Consejo Nacional de Investigaciones Científicas y Técnicas, Mar del Plata, Buenos Aires, Argentina; Fundación para Investigaciones Biológicas Aplicadas, Argentina. Electronic address: lcuratti@fiba.org.ar.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Curatti
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D016948:Azotobacter vinelandii / Q000201:enzymology / Q000235:genetics; D020134:Catalytic Domain; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism; D060847:Metabolic Engineering / Q000379:methods*; D058086:Microalgae / Q000254:growth & development*; D059013:Microbial Consortia; D009586:Nitrogen Fixation / Q000235:genetics*; D017354:Point Mutation
chemical_list: D000641:Ammonia; D005974:Glutamate-Ammonia Ligase
keywords: Ammonium excretion; Fertilizer; Microalgae biomass; Nitrogen assimilation; Nitrogen fixation; Synthetic consortia