Denitrification activity of Bradyrhizobium sp. isolated from argentine soybean cultivated soils.

LETICIA ANDREA FERNÁNDEZ, ELDA BEATRIZ PEROTTI, MARCELO ANTONIO SAGARDOY, MARISA ANAHÍ GÓMEZ.

WORLD JOURNAL OF MICROBIOLOGY & BIOTECHNOLOGY

Springer Netherlands

Lugar: Netherlands; Año: 2008 vol. 24 p. 2577 - 2585

0959-3993

Two hundred and fifty strains, all of them representatives of native Bradyrhizobium sp., isolated from soils cultivated with soybean have been characterized by their denitrification activity. In addition, the denitrification potential of those soils was also measured by evaluating the most-probable-number (MPN) of denitrifying bacteria and the denitrification enzyme assay (DEA). Of the 250 isolates tested, 73 were scored as probably denitrifiers by a preliminary screening method. Only 41 were consider denitrifiers because produced gas bubbles in Durham tubes, cultures reached an absorbance of more than 0.1 and NO3- and NO2- were not present. Ten of these 41 were selected to confirm denitrification and to study denitrification genes. According to N2O production and cell protein concentration with NO3-, the isolates could be differentiated in three categories of denitrifiers. The presence of the napA, nirK, norC and nosZ genes was detected by production of a diagnostic PCR product using specific primers. RFLP from the 16S-23S rDNA spacer region (IGS) revealed that denitrifiers strains could be characterized as Bradyhrizobium japonicum and strains which were non-respiratory denitrifiers as B. elkanii.