Identification and synergetic mechanism of TCE, H2 and O2 metabolic microorganisms in the joint H2/O2 system

Abstract

The sole H2 and O2 usually promote chlorinated hydrocarbons (CHCs) biotransformation by several mechanisms, including reductive dechlorination and aerobic oxidation. However, the mechanism of the CHCs transformation in joint H2 and O2 system (H2/O2 system) is still unclear. In this study, the degradation kinetics of trichloroethene (TCE) were investigated and DNA stable isotope probing (DNA-SIP) were used to explore the synergistic mechanism of functional microorganisms on TCE degradation under the condition of H2/O2 coexistence. In the H2/O2 microcosm, TCE was significantly removed by 13.00 μM within 40 days, much higher than N2, H2 and O2 microcosms, and 1,1-DCE was detected as an intermediate. DNA-SIP technology identified three anaerobic TCE metabolizers, five aerobic TCE metabolizers, nine hydrogen-oxidizing bacteria (HOB), some TCE metabolizers utilizing limited O2, and some anaerobic dechlorinating bacteria reductively using H2 to dechlorinate TCE. It is also confirmed for the first time that 3 OUTs belonging to Methyloversatilis and SH-PL14 can simultaneously utilize H2 and O2 as energy sources to grow and metabolize TCE or 1,1-DCE. HOB may provide carbon sources or electron acceptors or donors for TCE biotransformation. These findings confirm the coexistence of anaerobic and aerobic TCE metabolizers and degraders, which synergistically promoted the conversion of TCE in the joint H2/O2 system. Our results provide more information about the functional microbe resources and synergetic mechanisms for TCE degradation.