Denitrification capacity of Bradyrhizobium sp. isolates from soils cultivated with soybean

FERNÁNDEZ, LETICIA; PEROTTI, ELDA; GÓMEZ, MARISA; SAGARDOY, MARCELO A.

BIOCELL

Inca Editorial

Lugar: Mendoza; Año: 2006 vol. 30 p. 404 - 404

0327-9545

Denitrification is the microbial process in which nitrogen oxides are used as alternative electron acceptors for energy production. Two criteria must be met for an organism to be called a denitrifier: N2O and N2 are products of nitrate reduction and this is coupled to a growth yield. The objective of the present work was to determine the phenotypic characteristic of denitrifying from Bradyrhizobium sp. isolates. They were obtained from 2 silt loam soils cultivated with soybean from Pergamino and Manfredi. Eleven isolates were analyzed, out of 41 which have been described previously (another work) as being qualitatively denitrifiers. The isolates were grown in tubes with septa for gas extraction containing Bergensen medium with 10 mM KNO3 (3 replicates) and incubated at 28ºC. The atmosphere was replaced with filter-sterilized N2 and C2H2 (1%). After 7 days of incubation, N2O production was quantified with gas chromatography and cells were harvested by centrifuging. Bacterial protein concentration was determined by the method of Bradford. We conclude that: (i) a great proportion of Bradyrhizobium sp. isolates significantly contribute to the denitrification capacity of the studied soils, (ii) the denitrifying ability differs among isolates from the cultivated soybean soils.