Lactobacillus buchneri subsp. silagei subsp. nov., isolated from rice grain silage

Area of Science:

• Microbiology
• Bacteriology
• Genomics

Background:

• Two bacterial strains, SG162^T and NK01, were isolated from silage.
• Initial 16S rRNA gene sequencing suggested they were Lactobacillus buchneri.

Purpose of the Study:

• To genomically and phenotypically characterize strains SG162^T and NK01.
• To determine if these strains represent a new subspecies of Lactobacillus buchneri.

Main Methods:

• Whole-genome sequencing for average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH).
• Polyphasic characterization including metabolic substrate utilization and growth conditions.
• Analysis of genes involved in carbon metabolism and γ-aminobutyric acid (GABA) production.

Main Results:

• Genomic analysis revealed SG162^T and NK01 form a distinct infraspecific subgroup, separate from L. buchneri DSM 20057^T.
• ANI values ranged from 99.4-99.7% within the subgroup and 96.9-97.0% against DSM 20057^T.
• The new strains showed enhanced substrate utilization and lacked genes for GABA production.

Conclusions:

• Strains SG162^T and NK01 represent a novel subspecies, Lactobacillus buchneri subsp. silagei subsp. nov.
• The type strain is SG162^T (=JCM 32599^T=DSM 107969^T).
• Strains CD034 and S42 are also reclassified under this new subspecies.