Coupling elemental mercury (Hg-0) oxidation, autotrophic denitrifying sulfur oxidation, and sulfur disproportionation offers technological potential for simultaneous Hg(0)and nitric oxide (NO) removal. This study shed light on simultaneous demercuration and denitration of flue gas by a sulfur-oxidizing membrane biofilm reactor (MBfR). Removal efficiency of Hg(0)and NO attained 92% and 83%, respectively in long-term operation. Taxonomic and metagenomic study revealed that a tremendous variety of Hg-0-oxidizing bacteria (MOB) (Thiobacillus,Truepera, etc.), denitrifying/sulfur-oxidizing bacteria (DSOB) (Thioalkalivibrio,Thauera, etc.), sulfur-disproportionating bacteria (SDB) (Desulfobulbus,Desulfomicrobium, etc.), and multi-functional bacteria (Halothiobacillus,Thiobacillus, etc.) significantly increased in abundance during growth under feeding of Hg(0)and NO in simulated flue gas. The comprehensive employment of sequential chemical extraction processes, inductive coupled mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy coupled to energy disperse spectroscopy confirmed that Hg(0)was finally biologically oxidized to crystallized metacinnabar (beta-HgS) extracellular micromolecular particles. Our findings provided mechanistic insights that MOB, DSOB, and multi-functional bacteria synergistically bio-oxidized Hg(0)as the initial electron donor to Hg(2+)and denitrified NO as the terminal electron acceptor to N-2. SDB disproportionated S(0)branched from S(2)O(3)(2-)into S(2-)and SO42-, and beta-HgS formation from Hg(2+)and disproportionation-derived S2-, thermodynamically favored Hg(0)bio-oxidation. This novel biotechnique can be a cost-effective and environmentally friendly alternative to flue gas Hg(0)and NO treatment.