Bradyrhizobium aeschynomenes sp. nov., a root and stem nodule microsymbiont of Aeschynomene indica

Li Sun, Zhenpeng Zhang, Xiaoyan Dong, Zhihong Tang, Bao Ju, Zongjun Du, Entao Wang, Zhihong Xie

Research output: Contribution to journalArticlepeer-review

Abstract

Aeschynomene indica has a distinctive symbiosis with Bradyrhizobium in which nodulation is Nod factor-independent. In this study, we characterised three Gram-negative and rod-shaped strains (83002T, 81013 and 83012) isolated from root nodules of Aeschynomene indica in Shandong Peninsula. The major cellular fatty acids of isolates were C16:0, C18:0, C18:1 ω7c 11-methyl, summed feature 3 and summed feature 8. The major polar lipids were phosphatidylethanolamine (PE), aminolipids (AL) and phosphatidylcholine (PC). Phylogenetic analysis based on the 16S rRNA locus showed that they belonged to the Bradyrhizobium genus, and shared the highest similarity to the type strains Bradyrhizobium oligotrophicum S58T and Bradyrhizobium denitrificans LMG 8443T. As expected, analysis of concatenated sequences of six housekeeping genes (atpD, recA, glnII, dnaK, gyrB, and rpoB) and nifH gene proposed that these three strains formed a distinct clade within the genus Bradyrhizobium. The highest average nucleotide identity and DNA-DNA hybridization values of the three strains in comparison to the closest Bradyrhizobium species were 87.5% and 65.3%, respectively, which are far below the threshold of species delineation, and thus confirmed the three strains as a new species. The genome size of strain 83002T is 7.52 Mbp, and the DNA G+C content is 65.42 mol%. Strain 83002T (=KCTC 82266T=MCCC 1K04775T) was chosen as the type strain of the new species, for which the name Bradyrhizobium aeschynomenes sp. nov. was proposed.

Original languageEnglish
Article number126337
JournalSystematic and Applied Microbiology
Volume45
Issue number4
DOIs
StatePublished - Jul 2022
Externally publishedYes

Keywords

  • Bradyrhizobium aeschynomenes sp. nov
  • Nod-independent
  • Nodules
  • Taxonomy

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