title: Expression of alginases and alginate polymerase genes in response to oxygen, and their relationship with the alginate molecular weight in Azotobacter vinelandii.
abstract: The transcription of genes involved in alginate polymerization and depolymerization, as well as the alginase activity (extracellular and intracellular) under oxygen-limited and non oxygen-limited conditions in cultures of A. vinelandii, was studied. Two levels of dissolved oxygen tension (DOT) (1% and 5%, oxygen-limited and non-oxygen-limited, respectively) strictly controlled by gas blending, were evaluated in a wild type strain. In cultures at low DOT (1%), in which a high molecular weight alginate (1200 kDa) was synthesized, the transcription levels of alg8 and alg44 (genes encoding alginate polymerase complex), and algX (encoding a protein involved in polymer transport through periplasmic space) were considerably higher as compared to cultures conducted at 5% DOT, under which an alginate with a low MW (42 kDa) was produced. In the case of genes encoding for intracellular and extracellular alginases, the levels of these transcripts were higher at 1% DOT. However, intracellular and extracellular alginase activity were lower (0.017 and 0.01 U/mg protein, respectively) in cultures at 1% DOT, as compared with the activities measured at 5% DOT (0.027 and 0.052 U/mg protein for intracellular and extracellular maximum activity, respectively). The low alginase activity measured in cultures at 1% DOT and the high level of transcription of genes constituting alginate polymerase complex might be mechanisms by which oxygen regulates the production of alginates with a high MW.
authors.affiliation: Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, 62210, Morelos, Mexico. celia@ibt.unam.mx
authors.forename: Celia
authors.initials: C
authors.lastname: Flores
authors.forename: Soledad
authors.initials: S
authors.lastname: Moreno
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Espín
authors.forename: Carlos
authors.initials: C
authors.lastname: Peña
authors.forename: Enrique
authors.initials: E
authors.lastname: Galindo
mesh_terms: D000464:Alginates / Q000737:chemistry / Q000378:metabolism*; D016948:Azotobacter vinelandii / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D001426:Bacterial Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018533:Biomass; D015964:Gene Expression Regulation, Bacterial; D007218:Industrial Microbiology; D008970:Molecular Weight; D010100:Oxygen / Q000494:pharmacology; D010101:Oxygen Consumption; D058105:Polymerization; D011133:Polysaccharide-Lyases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000464:Alginates; D001426:Bacterial Proteins; D011133:Polysaccharide-Lyases; C016158:poly(beta-D-mannuronate) lyase; D010100:Oxygen