title: A N2-fixing endophytic Burkholderia sp. associated with maize plants cultivated in Mexico.
abstract: In the frame of a survey of potentially endophytic N2-fixing Burkholderia associated with maize in Mexico, its country of origin, the soil of an indigenous maize field near Oaxaca was studied. Under laboratory conditions, plant seedlings of two ancient maize varieties were used as a trap to select endophyte candidates from the soil sample. Among the N2 fixers isolated from inside plant tissues and able to grow on PCAT medium, the most abundant isolates belonged to genus Burkholderia (API 20NE, rrs sequences). Representative isolates obtained from roots and shoots of different plants appeared identical (rrs and nifH RFLP), showing that they were closely related. In addition, their 16S rDNA sequences differed from described Burkholderia species and, phylogenetically, they constituted a separate deep-branching new lineage in genus Burkholderia. This indicated that these isolates probably constituted a new species. An inoculation experiment confirmed that these N2-fixing Burkholderia isolates could densely colonize the plant tissues of maize. More isolates of this group were subsequently obtained from field-grown maize and teosinte plants. It was hypothesized that strains of this species had developed a sort of primitive symbiosis with one of their host plants, teosinte, which persisted during the domestication of teosinte into maize.
authors.affiliation: Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Cuernavaca Morelos.
authors.forename: Paulina
authors.initials: P
authors.lastname: Estrada
authors.forename: Patrick
authors.initials: P
authors.lastname: Mavingui
authors.forename: Benoit
authors.initials: B
authors.lastname: Cournoyer
authors.forename: Fanette
authors.initials: F
authors.lastname: Fontaine
authors.forename: Jacques
authors.initials: J
authors.lastname: Balandreau
authors.forename: Jesus
authors.initials: J
authors.lastname: Caballero-Mellado
mesh_terms: D001431:Bacteriological Techniques; D019117:Burkholderia / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008800:Mexico; D009586:Nitrogen Fixation; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology*; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D021521:Ribotyping; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013045:Species Specificity; D003313:Zea mays / Q000382:microbiology*
chemical_list: D012336:RNA, Ribosomal, 16S