文献类型： 外文期刊

作者： Jihed Hsouna;Takwa Gritli;Houda Ilahi;Jia Cheng Han;Walid Ellouze;Xiao Xia Zhang;Maroua Mansouri;Praveen Rahi;Mustapha Missbah El Idrissi;Mouad Lamrabet;Pierre Emmanuel Courty;Daniel Wipf;Abdelkader Bekki;James T. Tambong;Bacem Mnasri

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关键词： Acacia saligna;nodules;rhizobia;Rhizobium aouanii;Rhizobium leguminosarum complex

期刊名称： International Journal of Systematic and Evolutionary Microbiology

ISSN： 1466-5026

年卷期： 2024 年 74 卷 9 期

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收录情况： SCIE（2024版）

摘要： Three bacterial strains, 1AS14IT, 1AS12I and 6AS6, isolated from root nodules of Acacia saligna, were characterized using a polyphasic approach. Phylogenetic analysis based on rrs sequences placed all three strains within the Rhizobium leguminosarum complex. Further phylogeny, based on 1 756 bp sequences of four concatenated housekeeping genes (recA, atpD, glnII and gyrB), revealed their distinction from known rhizobia species of the R. leguminosarum complex (Rlc), forming a distinct clade. The closest related species, identified as Rhizobium laguerreae, with a sequence identity of 96.4% based on concatenated recAatpDglnII-gyrB sequences. The type strain, 1AS14IT, showed average nucleotide identity (ANI) values of 94.9, 94.3 and 94.1% and DNA–DNA hybridization values of 56.1, 57.4 and 60.0% with the type strains of closest known species: R. laguerreae, Rhizobium acaciae and ‘Rhizobium indicum’, respectively. Phylogenomic analyses using 81 up-to-date bacteria core genes and the Type (Strain) Genome Server pipeline further supported the uniqueness of strains 1AS14IT, 1AS12I and 6AS6. The relatedness of the novel strains to NCBI unclassified Rhizobium sp. (396 genomes) and metagenome-derived genomes showed ANI values from 76.7 to 94.8% with a species-level cut-off of 96%, suggesting that strains 1AS14I, 1AS12I and 6AS6 are a distinct lineage. Additionally, differentiation of strains 1AS14IT, 1AS12I and 6AS6 from their closest phylogenetic neighbours was achieved using phenotypic, physiological and fatty acid content analyses. Based on the genomic, phenotypic and biochemical data, we propose the establishment of a novel rhizobial species, Rhizobium aouanii sp. nov., with strain 1AS14IT designated as the type strain (=DSM 113914T=LMG 33206T). This study contributes to the understanding of microbial diversity in nitrogen-fixing symbioses, specifically within Acacia saligna ecosystems in Tunisia.

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