Name: Ilyobacter delafieldii Janssen and Harfoot 1991

Category: Species

Proposed as: sp. nov.

Etymology: de.la.fiel’di.i. N.L. gen. masc. n. delafieldii, of Delafield, named after F.P. Delafield

Pronunciation, gender: de-la-FIEL-di-i, masculine

Type strain: 10cr1; ATCC 49679; DSM 5704; LMG 16218

See detailed strain information at

16S rRNA gene: FR733681 Analyse FASTA

Effective publication: Janssen PH, Harfoot CG. Ilyobacter delafieldii sp. nov., a metabolically restricted anaerobic bacterium fermenting PHB. Arch. Microbiol. 1990; 154:253-259.

IJSEM list: Anonymous. Validation list no. 37. Validation of publication of new names and new combinations previously effectively published outside the IJSB. Int J Syst Bacteriol 1991; 41:331.

Nomenclatural status: validly published under the ICNP

Taxonomic status: correct name

Risk group: 1

• Notes:
  • 😷 The risk group for Canada has been imported on 2024-02-27. The full classification is: risk group = 1, note = "Security sensitive biological agent: No - Terrestrial animal pathogen under Canadian Food Inspection Agency authority: No". — The risk group for Swiss Confederation has been imported on 2024-02-01. The full classification is: risk group = 1. — The risk group for Germany has been imported on 2023-10-29. The full classification is: risk group = 1. — If in doubt, use the risk group given in the regulations for your country and, if these are not available, use the risk group given in the catalogue of the culture collection from which you have obtained or intend to obtain the strain.
  • 🎓 Name mentioned 3 times in PubMed until 2025-06-04.
  • 🧍 According to Ludwig et al. (2021), this "species affiliates away from the type species, and instead with one of the branches of the Clostridiaceae". Publication: Ludwig W, Viver T, Westram R, Francisco Gago J, Bustos-Caparros E, Knittel K, Amann R, Rossello-Mora R. Release LTP_12_2020, featuring a new ARB alignment and improved 16S rRNA tree for prokaryotic type strains. Syst Appl Microbiol 2021; 44:126218.
  • 🧍 Yarza et al. (2013) expected for accession FR733681, originating from the alleged type-strain deposit DSM 5704, an affiliation with Fusobacteriaceae (Fusobacteria) but observed an affiliation with Clostridiaceae (Firmicutes) and 98.8% similarity against Clostridium homopropionicum. Publication: Yarza P, Sproer C, Swiderski J, Mrotzek N, Spring S, Tindall BJ, Gronow S, Pukall R, Klenk HP, Lang E, et al. Sequencing orphan species initiative (SOS): Filling the gaps in the 16S rRNA gene sequence database for all species with validly published names. Syst Appl Microbiol 2013; 36:69-73.
  • 🧍 The 16S rRNA gene sequence of the type strain shows an unexpected affiliation with the family Clostridiaceae (98.8% similarity against Clostridium homopropionicum). Publication: Yarza P, Sproer C, Swiderski J, Mrotzek N, Spring S, Tindall BJ, Gronow S, Pukall R, Klenk HP, Lang E, et al. Sequencing orphan species initiative (SOS): Filling the gaps in the 16S rRNA gene sequence database for all species with validly published names. Syst Appl Microbiol 2013; 36:69-73.

Parent taxon: Ilyobacter Stieb and Schink 1985

Assigned by: Janssen PH, Harfoot CG. Ilyobacter delafieldii sp. nov., a metabolically restricted anaerobic bacterium fermenting PHB. Arch. Microbiol. 1990; 154:253-259.

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Record number: 777023