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

Two Gram-stain-positive, rod-shaped, non-motile, non-spore-forming, catalase-negative bacteria, designated strains SG162 T and NK01, were isolated from Japanese rice grain silage and total mixed ration silage, respectively. They were initially identified as Lactobacillus buchneri based on the 16S rRNA gene sequence similarities. However, the two strains were separated into a distinct clade from L. buchneri DSM 20057 T (=JCM 1115 T ) through whole-genome sequence-based characterization, forming an infraspecific subgroup together with strains CD034 and S42, whose genomic sequences were available in the public sequence database. Strains within the subgroup shared 99.4–99.7 % average nucleotide identity (ANI) and 97.5–99.0 % digital DNA–DNA hybridization (dDDH) with each other, albeit 96.9–97.0 % ANI and 76.0–76.6 % dDDH against DSM 20057 T . Strains SG162 T and NK01 could utilize more substrates as sole carbon sources than DSM 20057 T , potentially owing to the abundance of genes involved in carbon metabolism, especially the Entner–Doudoroff pathway. The inability of γ-aminobutyric acid (GABA) production was evidenced by the lack of glutamate decarboxylase and glutamate/GABA antiporter genes in the new subgroup strains. Strain SG162 T grew at 10–45 °C (optimum, 30 °C), pH 3.5–8.0, and 0–8 % (w/v) NaCl. Its genomic DNA G+C content was 44.1 mol%. The predominant fatty acids were C 16 : 0 , C 19 : 0 cyclo ω8 c , and summed feature 8. On the basis of the polyphasic characterization findings, strains SG162 T and NK01 represent a novel subspecies of L. buchneri , for which the name Lactobacillus buchneri subsp. silagei subsp. nov. is proposed. The type strain is SG162 T (=JCM 32599 T =DSM 107969 T ), and strains CD034 and S42 are also transferred to L. buchneri subsp. silagei .