Isolation and Characterization of Sporobacter termitidis gen. nov., sp. nov., from the Digestive Tract of the Wood-Feeding Termite Nasutitermes lujae

Researchers isolated a novel anaerobic bacterium designated Sporobacter termitidis strain SYRT from the digestive tract of wood-feeding termites (Nasutitermes lujae). This gram-positive, spore-forming, slightly curved rod exclusively metabolizes specific methylated aromatic compounds including trimethoxycinnamate, sinapate, and ferulate, but cannot use carbohydrates, alcohols, or fatty acids. The organism requires yeast extract for growth and metabolizes these aromatic substrates to acetate as the primary end product. When sulfide or cysteine were present, the bacterium produced dimethyl sulfide and methanethiol as intermediary products. Strain SYRT grew optimally at 32–35°C and pH 6.7–7.2. Phylogenetic analysis based on 16S rRNA gene sequencing indicated the isolate was distantly related to Eubacterium species and represented a novel genus within the low-G+C gram-positive clostridial group. With 57 mol% guanine-plus-cytosine content, distinctive physiological properties, and unique aromatic compound degradation capabilities, this bacterium was formally described as a new species in a new genus, contributing to understanding of lignin monomer metabolism in termite microbial ecosystems.

Key findings

• Sporobacter termitidis is a novel obligately anaerobic bacterium isolated from termite hindguts that uniquely cleaves aromatic rings of specific methylated compounds while producing only acetate
• The organism degrades tri- and disubstituted methoxyaromatic compounds but not monosubstituted variants, indicating substrate specificity related to methoxy group positioning
• Unlike related bacteria, S. termitidis produces dimethyl sulfide and methanethiol from methylated aromatic substrates in presence of sulfide or cysteine
• 16S rRNA phylogenetic analysis places this isolate in the low-G+C gram-positive clostridial group, representing a new genus distinct from Eubacterium and other known taxa
• The bacterium does not evolve hydrogen or methane, distinguishing it metabolically from other anaerobic aromatic-degrading bacteria in termite guts