Nitrogen-fixing Klebsiella variicola in feces from herbivorous tortoises

Abstract

Animals feeding on plants (herbivorous) may have nutritional deficiencies and use bacterial nitrogen fixation in guts to compensate unbalanced diets with high carbon and low nitrogen. Using the acetylene reduction assay we searched for nitrogen fixation in the feces from several herbivorous animals in captivity. We detected acetylene reduction in feces from two African spurred tortoises, Centrochelys sulcata and in feces from six Gopherus berlandieri tortoises and isolated nitrogen-fixing klebsiellas from them. Additionally, we performed a gut metagenomic study with Illumina sequencing from a healthy Mexican G. berlandieri tortoise, and the nif genes identified in the feces microbiome matched those from Klebsiella variicola. Fecal bacterial composition from tortoises was similar to that reported from other reptilian guts.