PS8-23. Isolation and Characterization of a Novel Pyramidobacter Species from the Rumen of Cattle.

Abstract Rumen microbes are essential for the fermentation of feed and the nutrition of cattle, yet many rumen bacteria remain poorly characterized due to the limited number of cultured isolates. Our aim was to isolate more species of bacteria, and we used a fermentor inoculated with rumen contents as the source of inoculum. From this inoculum, we isolated a novel strain (N5) under strict anaerobic conditions using reinforced clostridial medium (RCM) agar. Based on 16S ribosomal RNA gene sequences, the closest relatives of this strain were Pyramidobacter piscolens W5455 and Pyramidobacter porci SM-530-WT-4B, sharing 97.3% and 95.4% sequence identity with strain N5. The closest relative from the rumen was Synergistes jonesii 78-1, sharing only 81.7% identity. The isolate consisted of coccoid cells occurring in short chains and grew under strictly anaerobic conditions from 28 to 44 °C and pH 5.5 to 8.5. When cultures were provided with carbohydrates, growth (optical density at 600 nm) was not stimulated (P > 0.6). However, pH decreased (P < 0.03) and volatile fatty acids were produced. This result was found for pentoses, hexoses, disaccharides, oligosaccharides, and polysaccharides. These findings indicate that strain N5 can metabolize a wide range of carbohydrates, in contrast to known Pyramidobacter and Synergistes. Together, the phylogenetic and physiological characteristics indicate that strain N5 represents a novel species of Pyramidobacter, expanding current knowledge of metabolic diversity within this genus and contributing to the characterization of previously uncultured rumen bacteria.