Carbon tetrachloride product shift in a methanogenic, iron-containing system

The transformation of carbon tetrachloride (CT) by Methanosarcina thermophila can be affected by the presence of elemental iron (Fe⁰). The transformation of CT by M. thermophila grown in the presence and absence of Fe⁰ (P and A, respectively) was investigated using ¹⁴C-CT. In P and A treatments, the main degradation products were chloroform (CF) and CO₂. The P treatment produced greater amounts of CF, but degraded it at a higher rate than the A treatment. Products were identified to determine if degradation occurred via hydrogenolysis, generating CF and dichloromethane, or hydrolytic reduction, generating CO. The presence of Fe⁰ reduces the extent to which CT is degraded by hydrolytic reduction. The greater amounts of CF and the lesser amounts of CO and CO₂ produced by systems pre-exposed to Fe⁰ suggest that Fe⁰ creates conditions that lead to more hydrogenolysis of CT than occurs in systems without pre-exposure to Fe⁰.