Metabolic profiling and genetic tool development in the mucosal bacterium Selenomonas sputigena

Selenomonas sputigena is an anaerobic mucosa-associated bacterium with dual roles in human health-acting as a pathobiont in periodontal disease and exhibiting protective effects in allergic airway inflammation. Despite its clinical significance, its metabolic functions and underlying mechanisms remain poorly defined.

This study aimed to systematically characterize S. sputigena's metabolic capacity and develop genetic tools for functional studies.

We reconstructed central carbon metabolic networks through in silico analysis. Growth kinetics, substrate utilization, and fermentation profiles were evaluated experimentally across five carbon sources: glucose, gluconate, glycerol, glutamate, and succinate. Expression of key metabolic genes was quantified by qRT-PCR. Native promoter constructs were developed and tested for GFP reporter expression.

Selenomonas sputigena displayed glucose-preferential growth with rapid consumption (0.70 ± 0.05 mM h⁻¹) and substantial acetate production (17.76 ± 2.05 mM). Gluconate and glycerol supported moderate growth, while glutamate and succinate were poorly utilized. Gene expression analysis revealed strong substrate-dependent regulation of glycolytic genes, with gap expression correlating with growth performance, while TCA cycle genes maintained constitutive basal expression. Four native promoters successfully drove reporter expression, with P_gap demonstrating superior performance as a growth-responsive reporter.

This study establishes the first comprehensive metabolic and genetic framework for S. sputigena, revealing glucose-dependent fermentation with high acetate production that may contribute to host interactions. The validated promoter system enables future investigations of host-microbe interactions and therapeutic applications in mucosal environments.