Effect of Flooding and the <i>nosZ</i> Gene in Bradyrhizobia on Bradyrhizobial Community Structure in the Soil

Abstract

We investigated the effects of the water status (flooded or non-flooded) and presence of the nosZ gene in bradyrhizobia on the bradyrhizobial community structure in a factorial experiment that examined three temperature levels (20°C, 25°C, and 30°C) and two soil types (andosol and gray lowland soil) using microcosm incubations. All microcosms were inoculated with Bradyrhizobium japonicum USDA6 T , B. japonicum USDA123, and B. elkanii USDA76 T , which do not possess the nosZ gene, and then half received B. diazoefficiens USDA110 T wt (wt for the wild-type) and the other half received B. diazoefficiens USDA110ΔnosZ. USDA110 T wt possesses the nosZ gene, which encodes N 2 O reductase; 110ΔnosZ, a mutant variant, does not. Changes in the community structure after 30-and 60-d incubations were investigated by denaturing-gradient gel electrophoresis and an image analysis. USDA6 T and 76 T strains slightly increased in non-flooded soil regardless of which USDA110 T strain was present. In flooded microcosms with the USDA110 T wt strain, USDA110 T wt became dominant, whereas in microcosms with the USDA110ΔnosZ, a similar change in the community structure occurred to that in non-flooded microcosms. These results suggest that possession of the nosZ gene confers a competitive advantage to B. diazoefficiens USDA110 T in flooded soil. We herein demonstrated that the dominance of B. diazoefficiens USDA110 T wt within the soil bradyrhizobial population may be enhanced by periods of flooding or waterlogging systems such as paddy-soybean rotations because it appears to have the ability to thrive in moderately anaerobic soil.

Genetic diversity and distribution of indigenous soybean-nodulating bradyrhizobia in the Philippines

“…This signifies that cultural management such as waterlogging may affect the population dominance of strains belonging cluster Bd110. This result is supported by our previous reports where it was observed that the dominance of cluster USDA110 T was enhanced by flooding condition in the soil (37) and that USDA110 cluster are dominant on fine-textured soil that are affected by water status and oxidation-reduction potential in the soil (36). Additionally, it was reported that the anaerobic condition in flooded soil of alluvial origin resulted in the dominance of USDA110 T (43) which is also similar our results.…”

“…By far, diverse species of bradyrhizobia were reported to be micro-symbionts of soybean such as and (3, 8, 16, 20, 34, 51, 55). Accordingly, many reports stated that soil pH, salinity, climate and cultural management influence the diversity and distribution of soybean bradyrhizobia (1, 5, 11, 22, 24, 37, 44, 54). High diversity of microorganisms in the soil plays an important role in maintaining soil health and vast, accurate information about this could lead to better crop productivity.…”

Anaerobic Reduction of Nitrate to Nitrous Oxide Is Lower in <i>Bradyrhizobium japonicum</i> than in <i>Bradyrhizobium diazoefficiens</i>

“…These findings suggested that B. diazoefficiens ( nosZ + ) is predominant in Gleysol soils and B. japonicum ( nosZ − ) in Andosols ( 23 ). Saeki et al ( 18 ) recently indicated that the possession of nosZ confers a competitive advantage to B. diazoefficiens in flooded soil; this is consistent with the predominance of nosZ + bradyrhizobia in Gleysol soils ( 23 ). Thus, the aim of the present study was to identify key physiological traits in denitrification that differentiate the distribution of B. diazoefficiens and B. japonicum in soybean fields in Japan.…”

Variation in the nitrous oxide reductase gene (nosZ)-denitrifying bacterial community in different primary succession stages in the Hailuogou Glacier retreat area, China

“…Our findings show that denitrification processes were initiated in the T0 site, representing the starting point of primary succession, as evidenced by the predominance of Mesorhizobium in the early stages (0 and 20 years); this genus has a strong nitrogen fixation ability and promotes plant growth (Velez et al, 2017). At the T2 site, Brachybacterium was the dominant genus, with a high nitrogen fixation and denitrification capacity; it mostly grows in acidic-neutral soil (Saeki et al, 2017). Pseudomonas was found in the three sites T0, T1, and T2; it has the ability to degrade cellulose, produce amylase, and dissolve calcium phosphate, and based on its antibacterial properties, it has a certain certain inhibitory effect on soil diseases (Meyer et al, 2017;Ramette et al, 2006;Almario et al, 2014).…”