title: The signaling protein MucG negatively affects the production and the molecular mass of alginate in Azotobacter vinelandii.
abstract: Azotobacter vinelandii is a soil bacterium that produces the polysaccharide alginate. In this work, we identified a miniTn5 mutant, named GG9, which showed increased alginate production of higher molecular mass, and increased expression of the alginate biosynthetic genes algD and alg8 when compared to its parental strain. The miniTn5 was inserted within ORF Avin07920 encoding a hypothetical protein. Avin07910, located immediately downstream and predicted to form an operon with Avin07920, encodes an inner membrane multi-domain signaling protein here named mucG. Insertional inactivation of mucG resulted in a phenotype of increased alginate production of higher molecular mass similar to that of mutant GG9. The MucG protein contains a periplasmic and putative HAMP and PAS domains, which are linked to GGDEF and EAL domains. The last two domains are potentially involved in the synthesis and degradation, respectively, of bis-(3'-5')-cyclic dimeric GMP (c-di-GMP), a secondary messenger that has been reported to be essential for alginate production. Therefore, we hypothesized that the negative effect of MucG on the production of this polymer could be explained by the putative phosphodiesterase activity of the EAL domain. Indeed, we found that alanine replacement mutagenesis of the MucG EAL motif or deletion of the entire EAL domain resulted in increased alginate production of higher molecular mass similar to the GG9 and mucG mutants. To our knowledge, this is the first reported protein that simultaneous affects the production of alginate and its molecular mass.
authors: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Morelos, México.
authors: Carlos Leonel
authors: CL
authors: Ahumada-Manuel
authors: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Morelos, México.
authors: Josefina
authors: J
authors: Guzmán
authors: Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Morelos, México.
authors: Carlos
authors: C
authors: Peña
authors: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Morelos, México.
authors: Elva
authors: E
authors: Quiroz-Rocha
authors: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Morelos, México.
authors: Guadalupe
authors: G
authors: Espín
authors: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Morelos, México. cinthia@ibt.unam.mx.
authors: Cinthia
authors: http://orcid.org/0000-0002-1807-3836
authors: C
authors: Núñez
mesh_terms: D000464:Alginates / Q000378:metabolism*; D016948:Azotobacter vinelandii / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D020723:Glucuronic Acid / Q000378:metabolism; D006603:Hexuronic Acids / Q000378:metabolism; D009876:Operon / Q000235:genetics
chemical_list: D000464:Alginates; D001426:Bacterial Proteins; D006603:Hexuronic Acids; C062025:bis(3',5')-cyclic diguanylic acid; D020723:Glucuronic Acid; D006152:Cyclic GMP
keywords: Alginate; Azotobacter; Molecular mass; c-di-GMP