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Analysis of the denitrification pathway and greenhouse gases emissions in Bradyrhizobium sp. strains used as biofertilizers in South America
Author(s) -
Obando M.,
CorreaGaleote D.,
CastellanoHinojosa A.,
Gualpa J.,
Hidalgo A.,
Alché J.D.,
Bedmar E.,
Cassán F.
Publication year - 2019
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.14233
Subject(s) - bradyrhizobium , bradyrhizobium japonicum , microbial inoculant , denitrification , biology , symbiosis , nitrogen fixation , microbiology and biotechnology , inoculation , rhizobiaceae , bacteria , chemistry , horticulture , genetics , nitrogen , organic chemistry
Aims Greenhouse gases are considered as potential atmospheric pollutants, with agriculture being one of the main emission sources. The practice of inoculating soybean seeds with Bradyrhizobium sp. might contribute to nitrous oxide (N 2 O) emissions. We analysed this capacity in five of the most used strains of Bradyrhizobium sp. in South America. Methods and Results We analysed the denitrification pathway and N 2 O production by Bradyrhizobium japonicum E109 and CPAC 15, Bradyrhizobium diazoefficiens CPAC 7 and B. elkanii SEMIA 587 and SEMIA 5019, both in free‐living conditions and in symbiosis with soybean. The in silico analysis indicated the absence of nosZ genes in B. japonicum and the presence of all denitrification genes in B. diazoefficiens strains, as well as the absence of nir K, nor C and nos Z genes in B. elkanii . The in planta analysis confirmed N 2 O production under saprophytic conditions or symbiosis with soybean root nodules. In the case of symbiosis, up to 26.1 and 18.4 times higher in plants inoculated with SEMIA5019 and E109, respectively, than in those inoculated with USDA110. Conclusions The strains E109, SEMIA 5019, CPAC 15 and SEMIA 587 showed the highest N 2 O production both as free‐living cells and in symbiotic conditions in comparison with USDA 110 and CPAC 7, which do have the nos Z gene. Although nor C and nos Z could not be identified in silico or in vitro in SEMIA 587 and SEMIA 5019, these strains showed the capacity to produce N 2 O in our experimental conditions. Significance and Impact of the Study This is the first report to analyse and confirm the incomplete denitrification capacity and N 2 O production in four of the five most used strains of Bradyrhizobium sp. for soybean inoculation in South America.