Nitrite　production　via　denitrification　has　been　regarded　as　a　key　approach　for　survival　of　anaerobic　ammonium　oxidation　(anammox)　bacteria.　Despite　the　important　carbon　substrate,　little　is　known　about　the　role　of　differential　genes　expression　and　extracellular　metabolite　regulation　among　diverse　microbial　communities.　In　this　study,　a　novel　alternating　feast-famine　strategy　was　proposed　and　demonstrated　to　efficiently　accumulate　nitrite　in　a　low-nitrogen　loading　rate　(NLR)　(0.2-0.8　kg　N/m　3　/d)　denitrification　system.　Highly　selective　expression　of　denitrifying　genes　was　revealed　as　key　regulators.　Interestingly,　in　absence　of　carbon　source　(ACS)　condition,　the　expression　of　narG　and　narI/V　genes　responsible　for　reduction　of　nitrate　to　nitrite　jumped　to　2.5　and　5.1　times　higher　than　that　in　presence　of　carbon　source　(PCS)　condition　with　carbon　to　nitrate　ratio　of　3.0.　This　fortunately　facilitated　a　rapid　nitrite　accumulation　once　acetate　was　added,　despite　a　significantly　down-regulated　narG　and　narI/narV　and　up-regulated　nirS　/　nirK　.　This　strategy　selected　Thauera　as　the　most　dominant　denitrifier　(50.2　%)　with　the　highest　contribution　to　narG　and　narI/narV　genes,　responsible　for　the　high　nitrite　accumulation.　Additionally,　extracellular　xylose,　pyruvate,　and　glucose　jointly　promoted　carbon-central　metabolic　pathway　of　key　denitrifiers　in　ACS　stage,　playing　an　important　role　in　the　process　of　self-growth　and　selective　enrichment　of　functional　bacteria.　The　relatively　rapid　establishment　and　robust　performance　obtained　in　this　study　shows　an　engineering-feasible　and　economically-favorable　solution　for　the　regulation　of　partial　denitrification　in　practical　application.