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INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY logo International Journal of Systematic and Evolutionary Microbiology

Volume 76, Issue 2

sp. nov., a novel plant growth-promoting rhizobacterium isolated from sulphur-rich soil in Spain Open Access

Abstract

During a screening of sulphur-oxidizing bacteria from different Spanish soils, a strain designated AFSI2.2 was isolated from the rhizosphere soil of a mulberry plant thriving in a sulphur-rich environment. Cells of this strain were Gram-stain-negative motile rods with flagella. Its taxonomic classification was determined through a polyphasic approach. Phylogenetic analysis of the 16S rRNA gene revealed that strain AFSI2.2 shares high similarity (99.64%) with certain species, suggesting that the isolate belongs to this genus. Whole-genome phylogeny showed that the novel strain forms a distinct lineage within the genus . Whole-genome analysis of AFSI2.2 exhibited average nucleotide identity values of 78.37–89.63% and digital DNA–DNA hybridization values of 21.90–38.90% with closely related species, both below the established thresholds for species delineation. The predominant cellular fatty acids of strain AFSI2.2 were C, Summed Feature 3 (C 6 and/or C 7) and Summed Feature 8 (C 7 and/or C 6). Apart from the ability of oxidizing inorganic sulphur compounds, AFSI2.2 presented further plant growth-promoting (PGP) activities such as production of indole-3-acetic acid and siderophores and 1-aminocyclopropane-1-carboxylate deaminase activity. Genes associated with these PGP traits, as well as with cytokinin and gamma-aminobutyric acid biosynthesis, were identified in the AFSI2.2 genome, supporting its potential as a PGP bacterium. In conclusion, phylogenetic, genomic, phenotypic and chemotaxonomic analyses support the classification of the isolate as a novel species within the genus , for which the name sp. nov. is proposed. The type strain is AFSI2.2 (=CECT 31217=CIP 112526).

  • Received:
  • Accepted:
  • Published Online:
Keyword(s): plant growth-promoting rhizobacteria , sulphur-rich soil and Variovorax palleresanus
Funding
This study was supported by the:
  • AFEPASA SAU (Award 41185)
    • Principal Award Recipient: NotApplicable
  • Department of Research and Universities of the Government of Catalonia (Award Industrial Doctorates Plan)
    • Principal Award Recipient: CristinaComas
  • AFEPASA SAU (Award 080102210003)
    • Principal Award Recipient: NotApplicable
© 2026 The Authors
  • This is an open-access article distributed under the terms of the Creative Commons Attribution License.
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2026-02-15

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Variovorax palleresanus sp. nov., a novel plant growth-promoting rhizobacterium isolated from sulphur-rich soil in Spain
Int J Syst Evol Microbiol 76, 007057 (2026); https://doi.org/10.1099/ijsem.0.007057
/content/journal/ijsem/10.1099/ijsem.0.007057
/content/journal/ijsem/10.1099/ijsem.0.007057
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