Summary auto-generated
This study examined the taxonomic status of Pseudomonas corrugata using a polyphasic approach on 27 strains. Numerical analysis of phenotypic data revealed two distinct groups (phena A and B) that differed in their ability to assimilate mesotartrate, 2-ketogluconate, and histamine. DNA-DNA hybridization showed high reassociation values (96.9% and 98.5%) within each group but only approximately 70% between groups—the threshold for bacterial species definition. The two groups were further differentiated through multiple molecular techniques including 16S rRNA sequence analysis, PCR-based fingerprinting, and heteroduplex mobility assay. Phenon A contained the original P. corrugata type strain, while phenon B represented a genetically and phenotypically distinct group. Phylogenetic analysis of 16S rDNA sequences confirmed that phenon B strains formed a separate clade. Based on these integrated findings, the authors propose Pseudomonas mediterranea as a new species for phenon B strains, with strain CFBP 5447T designated as the type strain. The G+C content of P. mediterranea is 60.2 mol%. Both P. corrugata and P. mediterranea were pathogenic on various plant hosts, causing pith necrosis symptoms.
Key findings
- Two genetically and phenotypically distinct groups were identified within what was previously classified as Pseudomonas corrugata, with DNA-DNA reassociation values of approximately 70% between groups.
- Phenon B strains could be reliably differentiated from phenon A strains by their ability to assimilate mesotartrate, 2-ketogluconate, and histamine.
- 16S rRNA sequence analysis and multiple DNA fingerprinting methods confirmed that phenon B represents a separate species-level lineage within the Pseudomonas genus.
- Pseudomonas mediterranea sp. nov. is proposed as a new species for phenon B strains, with type strain CFBP 5447T (G+C content 60.2 mol%).
- Both P. corrugata and P. mediterranea produce identical pathogenic symptoms of pith necrosis in multiple plant hosts including tomato, pepper, eggplant, and tobacco.
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Abstract
To re-examine the taxonomic status of Pseudomonas corrugata, 27 strains of this species were studied using a polyphasic approach. Numerical analysis of phenotypic data revealed two phena, A (including the P. corrugata type strain) and B, which could be clearly differentiated by the assimilation of mesotartrate, 2-ketogluconate and histamine. The mean DNA reassociation values with labelled DNA of P. corrugata type strain CFBP 2431T (phenon A) and strain CFBP 5447T (phenon B) were high for strains belonging to the same phenon (96.9 and 98.5%, respectively), whereas the DNA relatedness between the two phena was assessed as being close to 70%, which represents the value that is accepted for the definition of a bacterial species. Phena A and B were also differentiated by means of DNA profiles generated by heteroduplex mobility assay of PCR products of 16S rDNA hypervariable region 2, HaeIII restriction of the amplified internal transcribed spacer, REP- and BOX-PCR profiles, and by PCR with two pairs of specific primers. A comparison of the 16S rRNA sequences of strains CFBP 5447T and CFBP 5458 from phenon B with the available sequences of Pseudomonas species showed that these strains formed a cluster distinct from the P. corrugata type strain. Thus, a new species, Pseudomonas mediterranea, is proposed for strains of phenon B. The type strain is strain CFBP 5447T (= ICMP 14184T); its G+C content is 60.2 mol%.