Bifidobacterium stercoris sp. nov., isolated from human faeces

Area of Science:

• Microbiology
• Bacteriology
• Genomics

Background:

• Human gut microbiota plays a crucial role in health.
• Bifidobacterium species are key commensal bacteria in the human gut.
• Accurate classification of bacterial species is essential for understanding their ecological roles and potential applications.

Purpose of the Study:

• To characterize and classify a novel bacterial strain isolated from human faeces.
• To determine the phylogenetic and genotypic relationship of the novel strain to known Bifidobacterium species.
• To propose a new species within the Bifidobacterium genus.

Main Methods:

• Isolation and cultivation of anaerobic, Gram-positive bacteria from human faecal samples.
• Phenotypic characterization including optimal growth temperature, enzyme activity tests (oxidase, catalase, fructose-6-phosphate phosphoketolase), and fermentation end-product analysis.
• Genotypic analysis involving 16S rRNA and hsp60 gene sequencing for phylogenetic analysis.
• DNA-DNA hybridization to assess genetic relatedness with closely related species.

Main Results:

• Strain Eg1(T) is an anaerobic, Gram-positive, non-motile, non-spore-forming bacterium with optimal growth at 37°C.
• Fermentation of glucose produced acetic acid and lactic acid in a molar ratio of approximately 3:2.
• Phylogenetic analysis based on 16S rRNA and hsp60 genes showed high similarity to Bifidobacterium adolescentis and Bifidobacterium ruminantium.
• Low DNA-DNA relatedness values (41% and 17%) distinguished strain Eg1(T) from B. adolescentis and B. ruminantium, respectively.
• The G+C content of strain Eg1(T) was 57.8 mol%.

Conclusions:

• Strain Eg1(T) represents a novel species within the Bifidobacterium genus.
• Based on phenotypic, genotypic, and phylogenetic data, Bifidobacterium stercoris sp. nov. is proposed.
• The type strain is Eg1(T) (=KCTC 5756(T) =JCM 15918(T)).