biostudies-literatureWang NNatural Science Foundation of Fujian ProvinceNational Natural Science Foundation of China2062https://www.ebi.ac.uk/biostudies/studies/S-EPMC12472895biostudies-literatureUnknown13(9)A novel Gram-negative bacterium, designated strain SN16^T, was isolated from a harmful algal bloom (HAB). Strain SN16^T exhibited potent, broad-spectrum algicidal activity against the colony-forming alga <i>Phaeocystis globosa</i> and eight other HAB-causing species, highlighting its potential as a promising candidate for the biological control of HABs. A phylogenetic analysis of 16S rRNA gene sequences placed strain SN16^T within the genus <i>Flagellimonas</i>. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain SN16^T and its relatives were 75.4-91.4% and 19.3-44.0%, respectively. These values fall below the established thresholds for species delineation, confirming that SN16^T represents aMicroorganisms&lt;i&gt;Flagellimonas algicida&lt;/i&gt; sp. Nov.: A Novel Broad-Spectrum Algicidal Bacterium Targeting Harmful Algal Bloom Species and Genomic Insights into Its Secondary Metabolites.PMC124728952023J01022U20B2037Wang NLiang YChen LLai QXu HZhou HChi Yfalse&lt;i&gt;Flagellimonas algicida&lt;/i&gt; sp. Nov.: A Novel Broad-Spectrum Algicidal Bacterium Targeting Harmful Algal Bloom Species and Genomic Insights into Its Secondary Metabolites.A novel Gram-negative bacterium, designated strain SN16^T, was isolated from a harmful algal bloom (HAB). Strain SN16^T exhibited potent, broad-spectrum algicidal activity against the colony-forming alga <i>Phaeocystis globosa</i> and eight other HAB-causing species, highlighting its potential as a promising candidate for the biological control of HABs. A phylogenetic analysis of 16S rRNA gene sequences placed strain SN16^T within the genus <i>Flagellimonas</i>. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain SN16^T and its relatives were 75.4-91.4% and 19.3-44.0%, respectively. These values fall below the established thresholds for species delineation, confirming that SN16^T represents a2025-01-01T00:00:00Z2025 Sep2026-07-04T03:15:03.766Z2026-07-04T03:12:57.29ZS-EPMC124728954101139410.3390/microorganisms13092062