Prevalence of oxalotrophy in the human microbiome

While oxalotrophy is relatively uncommon, the broader capacity for oxalate degradation is more widespread. Notably, the genes frc and oxc are frequently found in close proximity within genomes, suggesting a selective advantage for organisms possessing this capability. Incomplete degradation of oxalate, a compound commonly found in the diet, can cause disease in humans, particularly affecting the kidney. Its concentration in the body depends on several factors, one of which is intestinal absorption, which is itself affected by oxalotrophy among enteric bacteria. Oxalotrophy in the human microbiome is poorly known. In this study, we perform a systematic search for the simultaneous presence of the three oxalotrophy genes, namely frc, oxc and oxlT. Thanks to the construction and validation of specific conservation models for all three genes, we were able to search for oxalotrophy in genomes and metagenomes associated with the human digestive tract, oral cavity, and lungs. We report that oxalotrophy-the capacity to use oxalate as an energy source-is a rare metabolic trait, mostly confined to the gut, and also find evidence that it can be acquired by horizontal gene transfer. By contrast, the capacity for oxalate degradation is more widespread, and two genes responsible for it (frc and oxc) are almost always close together in the genome, suggesting selection pressure.