title: Denitrification ability of rhizobial strains isolated from Lotus sp.
abstract: Ten rhizobial strains isolated from Lotus sp. have been characterized by their ability to denitrify. Out of the 10 strains, the five slow-growing isolates grew well under oxygen-limiting conditions with nitrate as a sole nitrogen source, and accumulated nitrous oxide in the growth medium when acetylene was used to inhibit nitrous oxide reductase activity. All five strains contained DNA homologous to the Bradyrhizobium japonicum nirK, norBDQ and nosZ genes. In contrast, fast-growing lotus rhizobia were incapable of growing under nitrate-respiring conditions, and did not accumulate nitrous oxide in the growth medium. DNA from each of the five fast-growing strains showed a hybridization band with the B. japonicum nirK gene but not with norBDQ and nosZ genes. Partial 16S rDNA gene sequencing revealed that fast-growing strains could be identified as Mesorhizobium loti species and the slow-growers as Bradyrhizobium sp.
authors.affiliation: Laboratorio de Bioquímica, Facultad de Agronomía, Universidad de la República, Avenida Garzón 780, 12900, Montevideo, Uruguay. jmonza@fagro.edu.uy
authors.forename: Jorge
authors.initials: J
authors.lastname: Monza
authors.forename: Pilar
authors.initials: P
authors.lastname: Irisarri
authors.forename: Pedro
authors.initials: P
authors.lastname: Díaz
authors.forename: Ma Jesús
authors.initials: MJ
authors.lastname: Delgado
authors.forename: Socorro
authors.initials: S
authors.lastname: Mesa
authors.forename: Eulogio J
authors.initials: EJ
authors.lastname: Bedmar
mesh_terms: D020561:Alphaproteobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D020369:Bradyrhizobium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D004269:DNA, Bacterial / Q000032:analysis; D004275:DNA, Ribosomal / Q000032:analysis; D000070116:Lotus / Q000382:microbiology*; D009566:Nitrates / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D009566:Nitrates; D012336:RNA, Ribosomal, 16S