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1.
Artículo en Inglés | MEDLINE | ID: mdl-39235833

RESUMEN

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 recA-atpD-glnII-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.


Asunto(s)
Acacia , Técnicas de Tipificación Bacteriana , ADN Bacteriano , Ácidos Grasos , Hibridación de Ácido Nucleico , Filogenia , ARN Ribosómico 16S , Rhizobium , Nódulos de las Raíces de las Plantas , Análisis de Secuencia de ADN , Rhizobium/genética , Rhizobium/clasificación , Rhizobium/aislamiento & purificación , ADN Bacteriano/genética , Acacia/microbiología , ARN Ribosómico 16S/genética , Ácidos Grasos/análisis , Túnez , Nódulos de las Raíces de las Plantas/microbiología , Genes Esenciales/genética , Genes Bacterianos , Composición de Base , Simbiosis
2.
Artículo en Inglés | MEDLINE | ID: mdl-37199717

RESUMEN

Three bacterial strains, 1AS11T, 1AS12 and 1AS13, members of the new symbiovar salignae and isolated from root nodules of Acacia saligna grown in Tunisia, were characterized using a polyphasic approach. All three strains were assigned to the Rhizobium leguminosarum complex on the basis of rrs gene analysis. Phylogenetic analysis based on 1734 nucleotides of four concatenated housekeeping genes (recA, atpD, glnII and gyrB) showed that the three strains were distinct from known rhizobia species of the R. leguminosarum complex and clustered as a separate clade within this complex. Phylogenomic analysis of 92 up-to-date bacterial core genes confirmed the unique clade. The digital DNA-DNA hybridization and blast-based average nucleotide identity values for the three strains and phylogenetically related Rhizobium species ranged from 35.9 to 60.0% and 87.16 to 94.58 %, which were lower than the 70 and 96% species delineation thresholds, respectively. The G+C contents of the strains were 60.82-60.92 mol% and the major fatty acids (>4 %) were summed feature 8 (57.81 %; C18 : 1 ω7c) and C18 : 1 ω7c 11-methyl (13.24%). Strains 1AS11T, 1AS12 and 1AS13 could also be differentiated from their closest described species (Rhizobium indicum, Rhizobium laguerreae and Rhizobium changzhiense) by phenotypic and physiological properties as well as fatty acid content. Based on the phylogenetic, genomic, physiological, genotypic and chemotaxonomic data presented in this study, strains 1AS11T, 1AS12 and 1AS13 represent a new species within the genus Rhizobium and we propose the name Rhizobium acaciae sp. nov. The type strain is 1AS11T (=DSM 113913T=ACCC 62388T).


Asunto(s)
Acacia , Rhizobium , Acacia/genética , Ácidos Grasos/química , Filogenia , Túnez , Nódulos de las Raíces de las Plantas/microbiología , Análisis de Secuencia de ADN , Composición de Base , ADN Bacteriano/genética , ARN Ribosómico 16S/genética , Técnicas de Tipificación Bacteriana , Nucleótidos
3.
Syst Appl Microbiol ; 45(4): 126343, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35759954

RESUMEN

Acacia saligna is an invasive alien species that has the ability to establish symbiotic relationships with rhizobia. In the present study, genotypic and symbiotic diversity of native rhizobia associated with A. saligna in Tunisia were studied. A total of 100 bacterial strains were selected and three different ribotypes were identified based on rrs PCR-RFLP analysis. Sequence analyses of rrs and four housekeeping genes (recA, atpD, gyrB and glnII) assigned 30 isolates to four putative new lineages and a single strain to Sinorhizobium meliloti. Thirteen slow-growing isolates representing the most dominant IGS (intergenic spacer) profile clustered distinctly from known rhizobia species within Bradyrhizobium with the closest related species being Bradyrhizobium shewense and Bradyrhizobium niftali, which had 95.17% and 95.1% sequence identity, respectively. Two slow-growing isolates, 1AS28L and 5AS6L, had B. frederekii as their closest species with a sequence identity of 95.2%, an indication that these strains could constitute a new lineage. Strains 1AS14I, 1AS12I and 6AS6 clustered distinctly from known rhizobia species but within the Rhizobium leguminosarum complex (Rlc) with the most closely related species being Rhizobium indicum with 96.3% sequence identity. Similarly, the remaining 11 strains showed 96.9 % and 97.2% similarity values with R. changzhiense and R. indicum, respectively. Based on nodC and nodA phylogenies and cross inoculation tests, these 14 strains of Rlc species clearly diverged from strains of Sinorhizobium and Rlc symbiovars, and formed a new symbiovar for which the name sv. "salignae" is proposed. Bacterial strains isolated in this study that were taxonomically assigned to Bradyrhizobium harbored different symbiotic genes and the data suggested a new symbiovar, for which sv. "cyanophyllae" is proposed. Isolates formed effective nodules on A. saligna.


Asunto(s)
Acacia , Bradyrhizobium , Rhizobium leguminosarum , Rhizobium , ADN Bacteriano/genética , Filogenia , ARN Ribosómico 16S/genética , Rhizobium leguminosarum/genética , Nódulos de las Raíces de las Plantas/microbiología , Análisis de Secuencia de ADN , Simbiosis/genética , Túnez
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