Characterization of the N2O-producing soil bacterium Rhizobium azooxidifex sp. nov.

Abstract

In the context of studying the bacterial community involved in nitrogen transformation processes in arable soils exposed to different extents of erosion and sedimentation in a long-term experiment (CarboZALF), a strain was isolated that reduced nitrate to nitrous oxide without formation of molecular nitrogen. The presence of the functional gene nirK, encoding the respiratory copper-containing nitrite reductase, and the absence of the nitrous oxide reductase gene nosZ indicated a truncated denitrification pathway and that this bacterium may contribute significantly to the formation of the important greenhouse gas N 2 O. Phylogenetic analysis based on the 16S rRNA gene sequence and the housekeeping genes recA and atpD demonstrated that the investigated soil isolate belongs to the genus Rhizobium. The closest phylogenetic neighbours were the type strains of Rhizobium. subbaraonis and Rhizobium. halophytocola. The close relationship with R. subbaraonis was reflected by similarity analysis of the recA and atpD genes and their amino acid positions. DNA-DNA hybridization studies revealed genetic differences at the species level, which were substantiated by analysis of the whole-cell fatty acid profile and several distinct physiological characteristics. Based on these results, it was concluded that the soil isolate represents a novel species of the genus Rhizobium, for which the name Rhizobium azooxidifex sp. nov. proposed.

Taxonomy of Rhizobiaceae revisited: proposal of a new framework for genus delimitation

“…The description is as provided by Behrendt et al . 2016 [74]. M. azooxidifex can be differentiated from other species of the genus Mycoplana based on OGRI calculations (ANI and dDDH).…”

Isolation, Identification and Characterization of Endophytic Bacterium Rhizobium oryzihabitans sp. nov., from Rice Root with Biotechnological Potential in Agriculture

“…Generally, most of the Rhizobium species have been isolated from the nodules on leguminous plants with the function of symbiotic nitrogen-fixing. However, some free-living Rhizobium strains have frequently been isolated from soil [2][3][4][5], water [6,7], rhizosphere and plant roots [8]. In addition, several Rhizobium species have been described on the basis of non-symbiotic strains isolated from rice recently, such as Rhizobium oryziradicis, Rhizobium rhizospherae, Rhizobium pseudoryzae, Rhizobium rhizoryzae, and Rhizobium oryzicola [9][10][11][12].…”

Rhizobium qitaiense sp. nov. and Mycoplana qihuense sp. nov. isolated from chickpea nodules

“…+, positive -, negative, ND, not detected. Data of 2, 5 and 6 were fromKang et al (2022),Ramana et al (2013),Behrendt et al (2016), respectively; data of 1, 3 and 4 are from this study.…”