Diversity of <i>Bradyrhizobium</i> in Non-Leguminous Sorghum Plants: <i>B. ottawaense</i> Isolates Unique in Genes for N₂O Reductase and Lack of the Type VI Secretion System

Abstract

Diverse members of Bradyrhizobium diazoefficiens, B. japonicum, and B. ottawaense were isolated from the roots of field-grown sorghum plants in Fukushima, and classified into "Rhizobia" with nodulated soybeans, "Free-living diazotrophs", and "Non-diazotrophs" by nitrogen fixation and nodulation assays. Genome analyses revealed that B. ottawaense members possessed genes for N 2 O reduction, but lacked those for the Type VI secretion system (T6SS). T6SS is a new bacterial weapon against microbial competitors. Since T6SS-possessing B. diazoefficiens and B. japonicum have mainly been isolated from soybean nodules in Japan, T6SS-lacking B. ottawaense members may be a cryptic lineage of soybean bradyrhizobia in Japan.

Assessment of Diazotrophic Proteobacteria in Sugarcane Rhizosphere When Intercropped With Legumes (Peanut and Soybean) in the Field

“…The high abundance of Pseudacidovorax was found in all cropping systems in the tillering stage and Bradyrhizobium in elongation and maturation, and these results showed that the functional shift of diazotrophs according to sugarcane growth. Several past reports also reported the association of Bradyrhizobium with the non-leguminous plants (Rouws et al, 2014a;Nyoki and Ndakidemi, 2018b;De Alencar et al, 2019;Hara et al, 2019;Wasai-Hara et al, 2020). Nyoki and Ndakidemi (2018b) described that inoculation of Bradyrhizobium with soybean and maize improves the crop health and yield significantly.…”

Comparative Metagenomics Reveals Microbial Signatures of Sugarcane Phyllosphere in Organic Management

“…Organic-specific taxa consisted of plant growth-promoting bacteria including N 2 -fixing bacteria [i.e., Mesorhizobium loti ( Shimoda et al, 2016 ) and Bradyrhizobium sp. SG09 ( Wasai-Hara et al, 2020 )], lactic acid bacterium L. plantarum , which had the capability to behave as a biocontrol agent against phytopathogens ( Daranas et al, 2019 ), and cellulase-degrading Bacillus cellulosilyticus ( Mead et al, 2013 ). The number of transition-specific taxa was the highest, suggesting that many microbes might act as intermediate agents of agricultural transformation from conventional practices to organic systems.…”

Unique Rhizobial Communities Dominated by <i>Bradyrhizobium liaoningense</i> and <i>Bradyrhizobium ottawaense</i> were Found in Vegetable Soybean Nodules in Osaka Prefecture, Japan

“…Previous studies reported that Ensifer melitoi, Rhizobium leguminosarum, and B. diazoefficiens possess nosZ-coding N 2 O reductase, and B. diazoefficiens may mitigate soil N 2 O emissions during the growth and post-growth periods of soybean crops on a field scale (Itakura et al, 2013;Torres et al, 2014;Akiyama et al, 2016;Catherine et al, 2022). B. ottawaense was also recently shown to possess nosZ (Mania et al, 2019;Wasai-Hara et al, 2020a). Sustainable agricultural technology with a low environmental impact is highly expected in the near future.…”

“…because B. liaoningense and B. ottawaense were dominant (Fig.2). B. ottawaense was only reported to have been isolated from the roots of sorghum in Japan(Wasai-Hara et al, 2020a), and no studies showed that B. liaoningense was dominant in soybean nodules. Therefore, to the best of our knowledge, the present study is the first to isolate B. liaoningense and B. ottawaense from soybean roots in Japan.…”