Formigenes

Formigenes refers to oxalate-degrading bacteria in the human gut, most notably the species Oxalobacter formigenes. These organisms metabolize oxalate for energy, thereby reducing both intestinal and urinary oxalate levels. Oxalobacter formigenes is a Gram-negative, strictly anaerobic rod that uses oxalate as its sole carbon and energy source, producing formate and carbon dioxide. It belongs to the family Oxalobacteraceae within the order Burkholderiales.

Ecology and transmission: Formigenes are part of the gut microbiota and vary in prevalence among individuals and populations. Colonization is influenced by age, diet, antibiotic exposure, and overall gut ecology. Antibiotics can suppress or eliminate O. formigenes, potentially increasing urinary oxalate excretion. Recolonization after antibiotic treatment is possible but not guaranteed.

Clinical relevance: By degrading oxalate in the gut, formigenes can lower intestinal absorption of oxalate and urinary excretion, potentially reducing the risk of calcium oxalate kidney stones. Probiotic use of Oxalobacter formigenes and related approaches have been investigated, but there is no widely approved oxalate-degrading probiotic at present. Some studies explore fecal microbiota transplantation as a way to restore oxalate-degrading capacity in hyperoxaluria or stone-prone patients; results are preliminary and context-dependent.

Discovery and terminology: Oxalobacter formigenes was described in the late 20th century. The term formigenes is sometimes used to refer to oxalate-degrading gut bacteria as a functional group.