Summary auto-generated
Researchers isolated a novel strictly anaerobic bacterium, strain Sjm18-20T, from the alimentary canal of Japanese corbicula clams. The bacterium is a Gram-negative, non-sporulating rod measuring 2.5–6.0 micrometers that exhibits oscillatory motility via peritrichous flagella and elongates to 30 micrometers after prolonged cultivation. It grows optimally at 30°C and pH 6.0–6.5, and ferments glucose and select pentoses (L-arabinose, D-ribose, D-xylose) to produce n-valeric acid as the major end product. Phylogenetic analysis based on 16S rRNA gene sequences places the organism in clostridial cluster IV, with closest uncultured relatives showing 92.6–92.9% sequence similarity to Oscillospira guilliermondii and cultivated neighbors Clostridium orbiscindens and C. viride at 91.3% and 89.1% similarity, respectively. The genomic DNA G+C content is 52.9 mol%. Based on distinct morphological, biochemical, physiological, and phylogenetic properties, the authors propose strain Sjm18-20T as a novel genus and species: Oscillibacter valericigenes gen. nov., sp. nov., with the type strain designated Sjm18-20T.
Key findings
- A novel strictly anaerobic bacterium (Oscillibacter valericigenes) was isolated from Japanese corbicula clam alimentary canals and represents a new genus in clostridial cluster IV.
- The bacterium produces n-valeric acid as the major fermentation end product from glucose and is Gram-negative, non-sporulating, and motile with peritrichous flagella.
- Phylogenetic analysis based on 16S rRNA gene sequences shows closest similarity to uncultured Oscillospira guilliermondii-like cells (92.6–92.9%) rather than cultivated Clostridium species.
- The organism exhibits oscillatory motility and cellular elongation to 30 micrometers after prolonged cultivation, traits similar to Oscillospira but differing by lack of endospores and multicellular structures.
- Optimal growth occurs at 30°C and pH 6.0–6.5, with the bacterium fermenting only glucose and certain pentoses among tested carbohydrates.
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Abstract
A mesophilic, strictly anaerobic bacterium, strain Sjm18-20T, was isolated from the alimentary canal of a Japanese corbicula clam. Cells of strain Sjm18-20T were Gram-negative, non-sporulating, straight to slightly curved rods, 2.5–6.0 µm long, and were motile with oscillatory movements by means of peritrichous flagella. Cells elongated to 30 µm after prolonged cultivation. Optimum growth was observed at 30 °C and pH 6.0–6.5. Growth occurred below 4.0 % (w/v) NaCl. Strain Sjm18-20T produced acid from D-glucose and a few pentoses such as L-arabinose, D-ribose and D-xylose. n-Valeric acid was the major end product from glucose. The genomic DNA G+C content of strain Sjm18-20T was 52.9 mol%. Phylogenetic analysis based on the 16S rRNA gene revealed that strain Sjm18-20T could be accommodated in clostridial cluster IV of the low-G+C-content Gram-positive bacteria and that the closest neighbour of this organism (92.6–92.9 % similarity) was the cloned 16S rRNA gene sequence of a not-yet cultured bacterium, thought to represent Oscillospira guilliermondii. The nearest cultivated neighbours of strain Sjm18-20T were Clostridium orbiscindens DSM 6740T and Clostridium viride T2-7T, with sequence similarities of 91.3 and 89.1 %, respectively. On the basis of phenotypic features and phylogenetic position, it is proposed that this isolate represents a novel species in a new genus, Oscillibacter valericigenes gen. nov., sp. nov. The type strain of Oscillibacter valericigenes is Sjm18-20T (=NBRC 101213T =DSM 18026T).