title: Azoarcus sp. CIB, an anaerobic biodegrader of aromatic compounds shows an endophytic lifestyle.
abstract: BACKGROUND
  Endophytic bacteria that have plant growth promoting traits are of great interest in green biotechnology. The previous thought that the Azoarcus genus comprises bacteria that fit into one of two major eco-physiological groups, either free-living anaerobic biodegraders of aromatic compounds or obligate endophytes unable to degrade aromatics under anaerobic conditions, is revisited here.
  
  
  RESULTS
  Light, confocal and electron microscopy reveal that Azoarcus sp. CIB, a facultative anaerobe β-proteobacterium able to degrade aromatic hydrocarbons under anoxic conditions, is also able to colonize the intercellular spaces of the rice roots. In addition, the strain CIB displays plant growth promoting traits such nitrogen fixation, uptake of insoluble phosphorus and production of indoleacetic acid. Therefore, this work demonstrates by the first time that a free-living bacterium able to degrade aromatic compounds under aerobic and anoxic conditions can share also an endophytic lifestyle. The phylogenetic analyses based on the 16S rDNA and nifH genes confirmed that obligate endophytes of the Azoarcus genus and facultative endophytes, such as Azoarcus sp. CIB, locate into different evolutionary branches.
  
  
  CONCLUSIONS
  This is the first report of a bacterium, Azoarcus sp. CIB, able to degrade anaerobically a significant number of aromatic compounds, some of them of great environmental concern, and to colonize the rice as a facultative endophyte. Thus, Azoarcus sp. CIB becomes a suitable candidate for a more sustainable agricultural practice and phytoremediation technology.
authors.affiliation: Department of Environmental Biology, Centro de Investigaciones Biológicas-CSIC, Madrid, Spain.
authors.forename: Helga
authors.initials: H
authors.lastname: Fernández
authors.affiliation: Department of Environmental Biology, Centro de Investigaciones Biológicas-CSIC, Madrid, Spain.
authors.forename: Nicolás
authors.initials: N
authors.lastname: Prandoni
authors.affiliation: Plant Protection Department, Instituto de Ciencias Agrarias-CSIC, Madrid, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Fernández-Pascual
authors.affiliation: Plant Protection Department, Instituto de Ciencias Agrarias-CSIC, Madrid, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Fajardo
authors.affiliation: Plant Protection Department, Instituto de Ciencias Agrarias-CSIC, Madrid, Spain.
authors.forename: César
authors.initials: C
authors.lastname: Morcillo
authors.affiliation: Department of Environmental Biology, Centro de Investigaciones Biológicas-CSIC, Madrid, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Díaz
authors.affiliation: Department of Environmental Biology, Centro de Investigaciones Biológicas-CSIC, Madrid, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Carmona
mesh_terms: D000693:Anaerobiosis; D020627:Azoarcus / Q000166:cytology / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D001673:Biodegradation, Environmental; D015169:Colony Count, Microbial; D060026:Endophytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D006841:Hydrocarbons, Aromatic / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000378:metabolism; D012275:Oryza / Q000166:cytology / Q000382:microbiology / Q000648:ultrastructure; D010710:Phosphates / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000382:microbiology / Q000648:ultrastructure; D012995:Solubility
chemical_list: D006841:Hydrocarbons, Aromatic; D007210:Indoleacetic Acids; D010710:Phosphates; C030737:indoleacetic acid; D009591:Nitrogenase