NC10 bacteria promoted methane oxidation coupled to chlorate reduction

The strictly anaerobic serum bottles were applied to investigate methane oxidation coupled to chlorate (ClO 3 − ) reduction (MO-CR) without exogenous oxygen. 0.35 mM ClO 3 − was consumed within 20 days at the reduction rate of 17.50 μM/d, over three times than that of ClO 4 − . Chlorite (ClO 2 − ) was not detected throughout the experiment and the mass recovery of Cl − was over 89%. Isotope tracing results showed most of 13 CH 4 was oxided to CO 2 , and the electrons recovery reached to 77.6%. Small amounts of 13 CH 4 was consumed for DOC production probably through aerobic methane oxidation process, with oxygen generated from disproportionation reaction. In pMMO (key enzyme in aerobic oxidation of methane) inhibition tests, ClO 3 − reduction rate was slowed to 7. 0 μmol/d by 2 mM C 2 H 2 , real-time quantitative PCR also showed the transcript abundance of pMMO and Cld were significantly dropped at the later period of experiment, indicating that the O 2 disproportionated from ClO 2 − was utilized to active CH 4 . NC10 bacteria Candidatus Methylomirabilis , related closely to oxygenic denitrifiers M. oxyfera , was detected in the system, and got enriched along with chlorate reduction. Several pieces of evidence supported that NC10 bacteria promoted CH 4 oxidation coupled to ClO 3 − reduction, these oxygenic denitrifiers may perform ClO 2 − disproportionation to produce O 2 , and then oxidized methane intracellularly.