biostudies-literatureUnknown16Zhao Y<h4>Introduction</h4><i>Riemerella anatipestifer</i> (<i>R. anatipestifer</i>) presents as a major pathogen causing septicemia among poultry. The complex serotype diversity and multidrug resistance of <i>R. anatipestifer</i> severely compromise infection prevention and treatment strategies. Bacteriophages and their endolysins represent a promising alternative strategy against <i>R. anatipestifer</i>.<h4>Methods</h4>The phage vB_RanS_GDF21 (GDF21) was isolated from feces of a duck farm, and its biological properties were characterized. Whole-genome sequencing was performed using the Illumina NovaSeq 6000 platform, followed by a bioinformatic analysis of the genome. The derived endolysin, LysGDF21 (encoded by <i>orf 65</i>), was expressed in <i>Escherichia coli</i> BL21 (DE3), and its anti-biofilm and antimicrobial activities were assessed.<h4>Results</h4>Transmission electron microscopy showed that phage GDF21 had an icosahedral symmetric head, and a long, non-contractile tail. It exhibited a 20 min eclipse period, burst size of 74 PFU/infected cell, and stability at pH 5-11 and temperatures below 50 °C. Whole-genome sequencing revealed that GDF21 possesses a double-stranded DNA genome with length of 46,925 bp and G+C content of 35.25%. Among the 75 predicted ORFs, 27 were functionally annotated and no genes associated with virulence or antibiotic resistance were identified. Phylogeny and classification analysis indicated that GDF21 is a member of the class Caudoviricetes and is closely related to Riemerella phage vB_RanS_CRP19. LysGDF21 significantly inhibited biofilm formation and disrupted mature biofilms in <i>R. anatipestifer</i>. When combined with EDTA, LysGDF21 exhibited broad antibacterial activity against <i>R. anatipestifer</i>.<h4>Conclusion</h4>The characterization of phage GDF21 enriches the phage database, while the potent anti-biofilm and antibacterial activities of LysGDF21 highlight its therapeutic potential against <i>R. anatipestifer</i> infections.Frontiers in microbiology1715949https://www.ebi.ac.uk/biostudies/studies/S-EPMC12845321biostudies-literatureCharacterization of a new lytic bacteriophage vB_RanS_GDF21 and its endolysin LysGDF21 with antimicrobial activity against <i>Riemerella anatipestifer</i>.PMC12845321Jiang YLiu YLi XLi YSi ZLu JCao SLiu CZhao YXue XfalseCharacterization of a new lytic bacteriophage vB_RanS_GDF21 and its endolysin LysGDF21 with antimicrobial activity against <i>Riemerella anatipestifer</i>.<h4>Introduction</h4><i>Riemerella anatipestifer</i> (<i>R. anatipestifer</i>) presents as a major pathogen causing septicemia among poultry. The complex serotype diversity and multidrug resistance of <i>R. anatipestifer</i> severely compromise infection prevention and treatment strategies. Bacteriophages and their endolysins represent a promising alternative strategy against <i>R. anatipestifer</i>.<h4>Methods</h4>The phage vB_RanS_GDF21 (GDF21) was isolated from feces of a duck farm, and its biological properties were characterized. Whole-genome sequencing was performed using the Illumina NovaSeq 6000 platform, followed by a bioinformatic analysis of the genome. The derived endolysin, LysGDF21 (encoded by <i>orf 65</i>), was expressed in <i>Escherichia coli</i> BL21 (DE3), and its anti-biofilm and antimicrobial activities were assessed.<h4>Results</h4>Transmission electron microscopy showed that phage GDF21 had an icosahedral symmetric head, and a long, non-contractile tail. It exhibited a 20 min eclipse period, burst size of 74 PFU/infected cell, and stability at pH 5-11 and temperatures below 50 °C. Whole-genome sequencing revealed that GDF21 possesses a double-stranded DNA genome with length of 46,925 bp and G+C content of 35.25%. Among the 75 predicted ORFs, 27 were functionally annotated and no genes associated with virulence or antibiotic resistance were identified. Phylogeny and classification analysis indicated that GDF21 is a member of the class Caudoviricetes and is closely related to Riemerella phage vB_RanS_CRP19. LysGDF21 significantly inhibited biofilm formation and disrupted mature biofilms in <i>R. anatipestifer</i>. When combined with EDTA, LysGDF21 exhibited broad antibacterial activity against <i>R. anatipestifer</i>.<h4>Conclusion</h4>The characterization of phage GDF21 enriches the phage database, while the potent anti-biofilm and antibacterial activities of LysGDF21 highlight its therapeutic potential against <i>R. anatipestifer</i> infections.2025-01-01T00:00:00Z20252026-06-13T05:29:53.161Z2026-06-13T03:09:01.971ZS-EPMC128453214160869110.3389/fmicb.2025.1715949