Cyanobacterial　blooms　have　profound　effects　on　the　structure　and　function　of　plankton　communities　in　inland　waters,　but　few　studies　have　focused　on　the　effects　of　microbial-based　processes　in　onecarbon　and　nitrogen　cycling　on　water　quality　improvement　following　the　bloom.　Here,　we　compared　the　structure　and　function　of　the　bacterial　community,　focusing　on　microbial　onecarbon　and　nitrogen　metabolisms　during　and　after　a　cyanobacterial　Microcystis　bloom　in　a　deep　subtropical　reservoir.　Our　data　showed　that　microbial　onecarbon　and　nitrogen　cycles　were　closely　related　to　different　periods　of　the　bloom,　and　the　changes　of　functional　genes　in　microbial　carbon　and　nitrogen　cycling　showed　the　same　consistent　trend　as　that　of　Methylomonas　sp.　With　the　receding　of　the　bloom,　the　abundance　of　Methylomonas　as　well　as　the　functional　genes　of　microbial　onecarbon　and　nitrogen　cycling　reached　the　peak　and　then　recovered.　Our　results　indicate　that　microbial　onecarbon　and　nitrogen　metabolisms　were　beneficial　to　the　recovery　of　water　quality　from　the　cyanobacterial　bloom.　This　study　lays　a　foundation　for　a　deep　understanding　of　the　cyanobacterial　decomposition　mediated　by　microbes　in　onecarbon　and　nitrogen　cycles　in　inland　freshwaters.　©　2022　Elsevier　B.V.