Peptostreptococcus equinus sp. nov., isolated from horse faeces.

Overview

• Researchers discovered and characterized a new bacterial species, named Peptostreptococcus equinus sp. nov., isolated from horse feces.
• This bacterium is part of the genus Peptostreptococcus and differs sufficiently from known species, supporting its status as a novel species.

Introduction to the Study

• The bacterium was isolated from the feces of a horse in Jeju, Republic of Korea.
• It is a Gram-positive, obligate anaerobic, non-spore-forming bacterium.
• Designated as strain CBA3647 by the researchers.

Phylogenetic Analysis

• Researchers analyzed the 16S rRNA gene sequences to determine the strain’s relationship to existing species.
• Strain CBA3647 formed a distinct lineage within the genus Peptostreptococcus, showing it was different from closely related species.
• The closest known species was ATCC 27337 with a 98.31% similarity, while other species had less than 98% similarity.
• This level of genetic difference supports the identification of strain CBA3647 as a novel species.

Genomic and Biochemical Characterization

• The DNA G+C content of the strain was measured at 30.0 mol%, which is a genomic characteristic important for classification.
• Digital DNA-DNA hybridization (dDDH) values between CBA3647 and six other Peptostreptococcus species were 24% or less—below the cut-off values typically used to define species boundaries.
• The bacterial cells were described as non-motile and oval-shaped cocci.
• The strain showed catalase-positive and oxidase-negative enzymatic activities.

Growth Conditions

• The strain grows optimally at 35°C, with a growth temperature range between 20°C and 40°C.
• Optimal growth occurred at neutral pH (pH 7), with a suitable range from pH 6 to 8.
• It tolerated sodium chloride concentrations up to 2% (w/v), with optimum growth at 1% NaCl.

Chemotaxonomic Traits

• The dominant fatty acids identified in strain CBA3647 were C iso and C fatty acids, important markers for bacterial taxonomy.

Conclusion and Taxonomic Significance

• Based on combined phenotypic, chemotaxonomic, and molecular evidence, strain CBA3647 was proposed as a novel species within the genus Peptostreptococcus.
• The researchers named this new species Peptostreptococcus equinus sp. nov., with its type strain designated as CBA3647 (=KACC 22891 = JCM 35846).
• This discovery expands the understanding of the diversity within Peptostreptococcus bacteria and their occurrence in equine gut microbiota.