Bradyrhizobium tunisiense sp. nov., a novel rhizobial species isolated from Acacia saligna nodules
Three slow-growing rhizobial strains, designated as 1AS2L<sup>T</sup>, 1AS20L and 1AS5L, were isolated from nodules of <i>Acacia saligna</i> in Borj Cedria, northern Tunisia. These strains, which belong to the symbiovar cyanophyllae, were characterized using a polyphasic approach. Phylogenetic analysis of the 16S rRNA (<i>rrs</i>) gene placed these strains within the genus <i>Bradyrhizobium</i>, specifically in the superclade associated with <i>Bradyrhizobium japonicum</i>. Further phylogenetic analysis using concatenated sequences of the <i>rec</i>A, <i>atp</i>D, <i>gln</i>II and <i>gyr</i>B genes (totalling 1,734 bp) positioned the strains in a distinct lineage, with <i>Bradyrhizobium shewense</i> identified as their closest related species, sharing a sequence identity of 95.2%. The type strain, 1AS2L<sup>T</sup>, exhibited average nucleotide identity values of 89.10%, 89.08% and 89.00% with the type strains of the closest valid species: <i>Bradyrhizobium frederickii</i>, <i>B. shewense</i> and <i>Bradyrhizobium ottawaense</i>, respectively. Additionally, digital DNA-DNA hybridization values confirmed the novelty of strain 1AS2L<sup>T</sup>, showing low similarity (38.0%-38.3%) with the type strains of the closest known species. Phylogenomic analyses based on up-to-date bacterial core genes, Type (Strain) Genome Server and the Genome Taxonomy Database (GTDB) pipelines further supported the uniqueness of the 1AS2L<sup>T</sup>, 1AS20L and 1AS5L strains. The GTDB analysis also robustly clustered two strains (SZCCT0449 and NSD-1) with our strains, suggesting putative members of the proposed novel species. The differentiation of these novel strains from their closest phylogenetic neighbours was also corroborated by phenotypic, physiological and fatty acid content analyses. Based on genomic, phenotypic and biochemical data, we propose the establishment of a novel species, <i>Bradyrhizobium tunisiense</i> sp. nov., with strain 1AS2L<sup>T</sup> (=LMG 33170<sup>T</sup>=DSM 114401<sup>T</sup>) as the type strain.
Authors
- Maroua Mansouri
- Takwa Gritli
- Xiao Xia Zhang
- Mikhail G. Sulman (ORCID: https://orcid.org/0000-0001-6543-617X)
- Jihed Hsouna
- Mustapha Missbah El Idrissi (ORCID: https://orcid.org/0000-0001-7003-9734)
- Abdelkader Bekki (ORCID: https://orcid.org/0000-0002-6258-5783)
- James T. Tambong (ORCID: https://orcid.org/0000-0001-5325-8038)
- Bacem Mnasri (ORCID: https://orcid.org/0000-0001-6385-4407)
- Walid Ellouze (ORCID: https://orcid.org/0000-0002-8749-9486)
- Houda Ilahi
- Pierre‐Emmanuel Courty (ORCID: https://orcid.org/0000-0003-2789-7818)
- Daniel Wipf (ORCID: https://orcid.org/0000-0001-7197-5612)
- Soufiane Alami (ORCID: https://orcid.org/0000-0001-6963-451X)
- Houda Zouagui (ORCID: https://orcid.org/0000-0002-8515-584X)
- Jia-Cheng Han
Institutions
- Mohammed V University (MA)
- Centre National de la Recherche Scientifique (FR)
- Agriculture and Agri-Food Canada (CA)
- Université Oran 1 Ahmed Ben Bella (DZ)
- University of Carthage (TN)
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (FR)
- Agroécologie (FR)
- Center of Biotechnogy of Borj Cédria (TN)
- Institute of Agricultural Resources and Regional Planning (CN)
- Institut Agro Dijon (FR)
- Chinese Academy of Agricultural Sciences (CN)
Publication Details
- Journal
- INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY
- Published
- 2025-06-19
- DOI
- https://doi.org/10.1099/ijsem.0.006807
- Citations
- 2
- Primary Topic
- Legume Nitrogen Fixing Symbiosis
- Type
- article
- Field-Weighted Citation Impact
- 3.50
Funders
- Agriculture and Agri-Food Canada