Caproicibacterium argilliputei sp. nov., a novel caproic acid producing anaerobic bacterium isolated from pit clay

An anaerobic, Gram-positive, rod-shaped, motile and spore-forming bacterium, designated strain ZCY20-5^T, was isolated from pit clay of Chinese strong-aroma type Baijiu (Chinese liquor). Phylogenetic analyses based on 16S rRNA gene and genome sequences showed that strain ZCY20-5^T belonged to the genus Caproicibacterium, family Oscillospiracheae, but it showed low similarity to the type species Caproicibacterium amylolyticum LBM18003^T (98.00 %) and Caproicibacterium lactatifermentans LBM19010^T (95.67 %). In anaerobic yeast extract medium, growth was observed at 20-45 °C (optimum, 35-40 °C), at pH 4.0-9.0 (optimum, pH 6.5-7.0) and with 0.0-2.0 % NaCl (w/v). The predominant fatty acids were C_16 : 0, C_14 : 0, C₁₃ 3-OH and C₁₆ 3-OH, and the major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, three phospholipids of unknown structure containing glucosamine and two unidentified phospholipids. Strain ZCY20-5^T exhibited an 81.32 % pairwise average nucleotide identity value, a 78.98 % average amino acid identity value and a 22.30 % digital DNA-DNA hybridization value compared to its closest relative C. amylolyticum LBM18003^T. Based on morphological, physiological, biochemical, chemotaxonomic, genotypic and phylogenetic results, strain ZCY20-5^T represents a novel species of Caproicibacterium, and the type strain is ZCY20-5^T (=MCCC 1A19399^T=KCTC 25590^T).