Rapid　and　sensitive　quantification　of　pathogenic　bacteria　is　highly　desired　for　environmental　health　supervision　and　food　safety　control.　Yet,　the　amplification　and　detection　of　bacteria　with　a　concentration　lower　than　102　cfu　mL−1　remains　a　great　challenge.　Here,　we　combined　an　allosteric　aptamer　(AAP)　with　a　gold　nanoparticle　(AuNP)　for　assembling　a　bridge-DNA　synthesis　system　(named　as　AuNP-BDS)　to　amplify　the　bacterial　signals.　The　AAP　and　its　paired　primer　(PP)　were　covalently　linked　to　two　different　AuNPs,　respectively:　one　named　as　AAP-AuNP　and　the　other　PP-AuNP.　Upon　recognition　of　the　antigen　from　the　pathogenic　bacteria,　AAP　alters　its　conformation　to　initiate　DNA　synthesis　on　the　AuNP　surface.　The　DNA　products　from　AAP-AuNP　and　PP-AuNP　form　bridges　to　each　other　through　base　pairing,　resulting　in　the　aggregation　and　colorimetric　response　of　the　AuNPs.　By　using　E.　coli　O157:H7　as　an　example,　the　AuNP-BDS　could　quantify　pathogenic　bacteria　in　water　with　a　concentration　as　low　as　10　cfu　mL−1　within　60　min　and　without　any　enrichment.　The　colorimetric　response　values　of　AuNP-BDS　were　found　to　be　linearly　related　to　the　bacterial　concentrations　in　the　range　of　10　to　103　cfu　mL−1.　Good　practicability　of　the　AuNP-BDS　in　quantifying　E.　coli　O157:H7　from　tap　water,　juices,　and　milks　was　demonstrated.　The　AuNP-BDS　could　be　exploited　to　facilitate　the　rapid　and　sensitive　quantification　of　pathogenic　bacteria　for　food　safety　control.　©　2023　The　Royal　Society　of　Chemistry.