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Research Article

Parabacteroides johnsonii sp. nov., isolated from human faeces

Sakamoto, Mitsuo, Kitahara, Maki, Benno, Yoshimi

International Journal of Systematic and Evolutionary Microbiology 2007; 57(2):293 · https://doi.org/10.1099/ijs.0.64588-0

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Summary auto-generated

This study describes the characterization and formal naming of a novel bacterial species, Parabacteroides johnsonii sp. nov., isolated from human feces. Strain M-165T was identified as a new species through comprehensive phenotypic, biochemical, and molecular analysis. The organism is an obligately anaerobic, Gram-negative rod that displays similar characteristics to the closely related species Parabacteroides merdae, sharing 98% 16S rRNA gene sequence similarity. However, key differences distinguish P. johnsonii from P. merdae, including distinct fermentation patterns for L-arabinose and L-rhamnose, catalase production, and pyroglutamic acid arylamidase activity. DNA-DNA hybridization experiments confirmed the genomic distinctiveness of the novel strain, showing less than 60% relatedness to P. merdae reference strains. The organism has a DNA G+C content of 47.6 mol% and produces succinic and acetic acids as major metabolic end products. The type strain M-165T has been deposited in microbial culture collections and designated with accession numbers JCM 13406T and DSM 18315T.

Key findings

  • Parabacteroides johnsonii sp. nov. is a novel anaerobic bacterium isolated from human feces, distinguished from closely related P. merdae by fermentation of L-arabinose and L-rhamnose and catalase production
  • DNA-DNA hybridization analysis revealed less than 60% genomic relatedness between P. johnsonii and P. merdae strains, confirming species-level distinctiveness despite 98% 16S rRNA gene sequence similarity
  • P. johnsonii has a DNA G+C content of 47.6 mol% and produces major metabolic end products of succinic and acetic acids with minor isovaleric and propionic acids
  • The organism is obligately anaerobic, Gram-negative, bile-tolerant, and exhibits catalase activity, differentiating it biochemically from P. merdae

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Abstract

A bacterial strain isolated from human faeces, M-165T, was characterized in terms of its phenotypic and biochemical features, cellular fatty acid profile, menaquinone profile and phylogenetic position (based on 16S rRNA gene sequence analysis). A 16S rRNA gene sequence analysis showed that the isolate was a member of the genus Parabacteroides. Strain M-165T was closely related to Parabacteroides merdae strains, showing 98 % sequence similarity. The strain was obligately anaerobic, non-pigmented, non-spore-forming, non-motile, Gram-negative, rod-shaped and was able to grow on media containing 20 % bile. Although the phenotypic characteristics of the strain M-165T were similar to those of P. merdae, the isolate could be differentiated from P. merdae by means of API 20A tests for L-arabinose and L-rhamnose fermentation. DNADNA hybridization experiments revealed the genomic distinctiveness of the novel strain with respect to P. merdae JCM 9497T (60 % DNADNA relatedness). The DNA G+C content of the strain is 47.6 mol%. On the basis of these data, strain M-165T represents a novel species of the genus Parabacteroides, for which the name Parabacteroides johnsonii sp. nov. is proposed. The type strain is M-165T (=JCM 13406T=DSM 18315T).