Given　the　significance　of　HCO3-　for　autotrophic　anammox　bacteria　(AnAOB),　excessive　HCO3-　was　always　provided　in　anammox-related　systems　and　engineering　applications.　However,　its　impact　mechanism　on　anammox　process　at　genome-level　remains　unknown.　This　study　firstly　established　an　anammox-centered　coupling　system　that　entails　heterotrophic　partial　denitrification　(PD)　and　hydrolytic　acidification　(A-PDHA)　fed　mainly　with　inorganic　carbon　(high　HCO3-　concentration　and　low　C/N　ratio).　Metagenomic　binning　and　metatranscriptomics　analyses　indicated　that　high　HCO3-　concentration　enhanced　expression　of　natural　most　efficient　phosphoenolpyruvate　(PEP)　carboxylase　within　AnAOB,　by　up　to　30.59　folds.　This　further　induced　AnAOB　to　achieve　highspeed　carbon-fixing　reaction　through　cross-feeding　of　phosphate　and　PEP　precursors　with　heterotrophs.　Additionally,　the　enhanced　activity　of　transporters　and　catalytic　enzymes　(up　to　4949-fold)　induced　by　low　C/N　ratio　enabled　heterotrophs　to　eliminate　extracellular　accumulated　energy　precursors　mainly　derived　from　carbon　fixation　products　of　AnAOB.　This　maintained　high-speed　carbon-fixing　reaction　within　AnAOB　and　supplemented　heterotrophs　with　organics.　Moreover,　assimilated　energy　precursors　stimulated　nitrogen　metabolism　enzymes,　especially　NO2-　reductase　(968.14　times),　in　heterotrophs.　This　established　an　energy-saving　PD-A　process　mediated　by　interspecies　NO　shuttle.　These　variation　resulted　in　efficient　nitrogen　removal　(＞95　%)　and　reduced　external　organic　carbon　demand　(67　%)　in　A-PDHA　system.　This　study　unveils　the　great　potential　of　an　anammox-centered　autotrophic-heterotrophic　coupling　system　for　achieving　cost-effective　nitrogen　removal　and　enhancing　carbon　fixation　under　excessive　HCO3-　doses.