The anaerobic and highly reductive conditions found in the ovine rumen are considered favorable for the degradation of the nitroaromatic explosives such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). In this study, we used stable-isotope-probing to determine the bacteria responsible for the degradation of RDX in the rumen. Results indicate 10 μg mL⁻¹ (45...