Rhizobium acaciae sp. nov., a new nitrogen-fixing symbiovar isolated from root nodules of Acacia saligna in Tunisia

• Published in: International journal of systematic and evolutionary microbiology Vol. 73; no. 5
• Main Authors: Hsouna, Jihed, Ilahi, Houda, Han, Jia-Cheng, Gritli, Takwa, Ellouze, Walid, Zhang, Xiao Xia, Mansouri, Maroua, Rahi, Praveen, El Idrissi, Mustapha Missbah, Lamrabet, Mouad, Oubla, M'hamed, Courty, Pierre Emmanuel, Wipf, Daniel, Tambong, James T, Mnasri, Bacem
• Format: Journal Article
• Language: English
• Published: England 18-05-2023
• Subjects: Acacia - genetics; Bacterial Typing Techniques; Base Composition; DNA, Bacterial - genetics; Fatty Acids - chemistry; Nucleotides; Phylogeny; Rhizobium; RNA, Ribosomal, 16S - genetics; Root Nodules, Plant - microbiology; Sequence Analysis, DNA; Tunisia; Tunisia; Rhizobium leguminosarum complex; Rhizobium acaciae; Acacia saligna; nodules
• ISSN: 1466-5034
• DOI: 10.1099/ijsem.0.005900

Three bacterial strains, 1AS11
, 1AS12 and 1AS13, members of the new symbiovar salignae and isolated from root nodules of
grown in Tunisia, were characterized using a polyphasic approach. All three strains were assigned to the
complex on the basis of
gene analysis. Phylogenetic analysis based on 1734 nucleotides of four concatenated housekeeping genes (
,
,
and
) showed that the three strains were distinct from known rhizobia species of the
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
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 %; C
 ω7
) and C
 ω7
11-methyl (13.24%). Strains 1AS11
, 1AS12 and 1AS13 could also be differentiated from their closest described species (
,
and
) 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 1AS11
, 1AS12 and 1AS13 represent a new species within the genus
and we propose the name
sp. nov. The type strain is 1AS11
(=DSM 113913
=ACCC 62388
).