title: Azotobacter vinelandii gene clusters for two types of peptidic and catechol siderophores produced in response to molybdenum.
abstract: OBJECTIVE
  To characterize the complementary production of two types of siderophores in Azotobacter vinelandii.
  
  
  RESULTS
  In an iron-insufficient environment, nitrogen-fixing A. vinelandii produces peptidic (azotobactin) and catechol siderophores for iron uptake to be used as a nitrogenase cofactor. Molybdenum, another nitrogenase cofactor, was also found to affect the production level of siderophores. Wild-type cells excreted azotobactin into molybdenum-supplemented and iron-insufficient medium, although catechol siderophores predominate in molybdenum-free environments. Two gene clusters were identified to be involved in the production of azotobactin and catechol siderophores through gene annotation and disruption. Azotobactin-deficient mutant cells produced catechol siderophores under the molybdenum-supplemented and iron-insufficient conditions, whereas catechol siderophore-deficient mutant cells extracellularly secreted excess azotobactin under iron-deficient condition independent of the concentration of molybdenum. This evidence suggests that a complementary siderophore production system exists in A. vinelandii.
  
  
  CONCLUSIONS
  Molybdenum was found to regulate the production level of two types of siderophores. Azotobacter vinelandii cells are equipped with a complementary production system for nitrogen fixation in response to a limited quantity of metals.
  
  
  CONCLUSIONS
  This is the first study identifying A. vinelandii gene clusters for the biosynthesis of two types of siderophores and clarifying the relationship between them.
authors.affiliation: Laboratory of Basic and Applied Molecular Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Yoneyama
authors.forename: M
authors.initials: M
authors.lastname: Yamamoto
authors.forename: W
authors.initials: W
authors.lastname: Hashimoto
authors.forename: K
authors.initials: K
authors.lastname: Murata
mesh_terms: D016948:Azotobacter vinelandii / Q000235:genetics* / Q000378:metabolism; D002396:Catechols / Q000378:metabolism; D003470:Culture Media; D018390:Gene Targeting; D005798:Genes, Bacterial; D007501:Iron / Q000378:metabolism; D008982:Molybdenum / Q000378:metabolism*; D005810:Multigene Family; D009154:Mutation; D010455:Peptides / Q000378:metabolism; D017262:Siderophores / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D002396:Catechols; D003470:Culture Media; D010455:Peptides; D017262:Siderophores; C041893:azotobactin; D008982:Molybdenum; D007501:Iron