Oxalobacter

Oxalobacter is a genus of Gram-negative, obligately anaerobic bacteria in the family Oxalobacteraceae. Its best studied member is Oxalobacter formigenes, which colonizes the gastrointestinal tract of humans and many animals.

Oxalobacter formigenes is typically rod-shaped and non-motile. It is strictly anaerobic and grows best in oxalate-containing environments.

The organism uses oxalate as its main energy and carbon source, oxidizing oxalate to formate and carbon dioxide. This metabolism relies on enzymes including oxalyl-CoA decarboxylase and formyl-CoA transferase. By degrading oxalate in the gut, it reduces the amount of oxalate available for absorption.

In humans, colonization rates vary by geographic region, age, diet, and antibiotic exposure. It is less common in some Western populations, and antibiotic use can reduce or eliminate colonization.

Several observational studies have linked colonization with lower urinary oxalate excretion and a reduced risk of calcium oxalate kidney stones, though results are not entirely consistent. Probiotic attempts to introduce Oxalobacter or modulate its levels have yielded mixed outcomes and are not yet standard clinical practice.

Taxonomy: Oxalobacter is the genus; Oxalobacter formigenes is the best characterized species. It resides within the phylum Proteobacteria and the family Oxalobacteraceae.