Journal of Microbiology

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Characterization of novel bacteriophages for effective phage therapy against Vibrio infections in aquaculture: Kira Moon, Sangdon Ryu, Seung Hui Song, Se Won Chun, Nakyeong Lee, Aslan Hwanhwi Lee; J. Microbiol. 2025;63(5):e2502009. Published online May 27, 2025; DOI: https://doi.org/10.71150/jm.2502009

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The widespread use of antibiotics in aquaculture has led to the emergence of multidrug-resistant pathogens and environmental concerns, highlighting the need for sustainable, eco-friendly alternatives. In this study, we isolated and characterized three novel bacteriophages from aquaculture effluents in Korean shrimp farms that target the key Vibrio pathogens, Vibrio harveyi, and Vibrio parahaemolyticus. Bacteriophages were isolated through environmental enrichment and serial purification using double-layer agar assays. Transmission electron microscopy revealed that the phages infecting V. harveyi, designated as vB_VhaS-MS01 and vB_VhaS-MS03, exhibited typical Siphoviridae morphology with long contractile tails and icosahedral heads, whereas the phage isolated from V. parahaemolyticus (vB_VpaP-MS02) displayed Podoviridae characteristics with an icosahedral head and short tail.

Whole-genome sequencing produced complete, circularized genomes of 81,710 bp for vB_VhaS-MS01, 81,874 bp for vB_VhaS-MS03, and 76,865 bp for vB_VpaP-MS02, each showing a modular genome organization typical of Caudoviricetes. Genomic and phylogenetic analyses based on the terminase large subunit gene revealed that although vB_VhaS-MS01 and vB_VhaS-MS03 were closely related, vB_VpaP-MS02 exhibited a distinct genomic architecture that reflects its unique morphology and host specificity. Collectively, these comparative analyses demonstrated that all three phages possess genetic sequences markedly different from those of previously reported bacteriophages, thereby establishing their novelty. One-step growth and multiplicity of infection (MOI) experiments demonstrated significant differences in replication kinetics, such as burst size and lytic efficiency, among the phages, with vB_VhaS-MS03 maintaining the most effective bacterial control, even at an MOI of 0.01. Additionally, host range assays showed that vB_VhaS-MS03 possessed a broader spectrum of activity, supporting its potential use as a stand-alone agent or key component of phage cocktails. These findings highlight the potential of region-specific phage therapy as a targeted and sustainable alternative to antibiotics for controlling Vibrio infections in aquaculture.

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Feed Additives in Aquaculture: Benefits, Risks, and the Need for Robust Regulatory Frameworks
Ekemini Okon, Matthew Iyobhebhe, Paul Olatunji, Mary Adeleke, Nelson Matekwe, Reuben Okocha
Fishes.2025; 10(9): 471. CrossRef

Genetic insights into novel lysis suppression by phage CSP1 in Escherichia coli: Moosung Kim, Sangryeol Ryu; J. Microbiol. 2025;63(4):e2501013. Published online April 29, 2025; DOI: https://doi.org/10.71150/jm.2501013

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Abstract PDF Supplementary Material

Lysis inhibition (LIN) in bacteriophage is a strategy to maximize progeny production. A clear plaque-forming mutant, CSP1C, was isolated from the turbid plaque-forming CSP1 phage. CSP1C exhibited an adsorption rate and replication dynamics similar to CSP1. Approximately 90% of the phages were adsorbed to the host cell within 12 min, and both phages had a latent period of 25 min. Burst sizes were 171.42 ± 31.75 plaque-forming units (PFU) per infected cell for CSP1 and 168.94 ± 51.67 PFU per infected cell for CSP1C. Both phages caused comparable reductions in viable E. coli cell counts at a low multiplicity of infection (MOI). However, CSP1 infection did not reduce turbidity, suggesting a form of LIN distinct from the well-characterized LIN of T4 phage. Genomic analysis revealed that a 4,672-base pairs (bp) DNA region, encompassing part of the tail fiber gene, CSP1_020, along with three hypothetical genes, CSP1_021, CSP1_022, and part of CSP1_023, was deleted from CSP1 to make CSP1C. Complementation analysis in CSP1C identified CSP1_020, CSP1_021, and CSP1_022 as a minimal gene set required for the lysis suppression in CSP1. Co-expression of these genes in E. coli with holin (CSP1_092) and endolysin (CSP1_091) resulted in lysis suppression. Lysis suppression was abolished by disrupting the proton motive force (PMF), supporting their potential role as antiholin. Additionally, CSP1_021 directly interacts with holin, suggesting that it may function as an antiholin. These findings identify new genetic factors involved in lysis suppression in CSP1, providing broader insights into phage strategies for modulating host cell lysis.

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Characterization and genome analyses of the novel phages targeting extraintestinal Escherichia coli clones ST131 and ST410
Md Shamsuzzaman, Yoon-Jung Choi, Shukho Kim, Jungmin Kim
International Microbiology.2025; 28(7): 2233. CrossRef

Research Article

Single nucleotide genome recognition and selective bacterial lysis using synthetic phages loaded with CRISPR-Cas12f1-truncated sgRNA: Ho Joung Lee, Song Hee Jeong, Sang Jun Lee; J. Microbiol. 2025;63(2):e2501012. Published online February 27, 2025; DOI: https://doi.org/10.71150/jm.2501012

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Abstract PDF Supplementary Material: Phage specificity primarily relies on host cell-surface receptors. However, integrating cas genes and guide RNAs into phage genomes could enhance their target specificity and regulatory effects. In this study, we developed a CRISPR-Cas12f1 system-equipped bacteriophage λ model capable of detecting Escherichia coli target genes. We demonstrated that synthetic λ phages carrying Cas12f1-sgRNA can effectively prevent lysogen formation. Furthermore, we showcased that truncating the 3'-end of sgRNA enables precise identification of single-nucleotide variations in the host genome. Moreover, infecting E. coli strains carrying various stx2 gene subtypes encoding Shiga toxin with bacteriophages harboring Cas12f1 and truncated sgRNAs resulted in the targeted elimination of strains with matching subtype genes. These findings underscore the ability of phages equipped with the CRISPR-Cas12f1 system to precisely control microbial hosts by recognizing genomic sequences with high resolution.

Journal Articles

Characterization of Newly Isolated Bacteriophages Targeting Carbapenem-Resistant Klebsiella pneumoniae: Bokyung Kim, Shukho Kim, Yoon-Jung Choi, Minsang Shin, Jungmin Kim; J. Microbiol. 2024;62(12):1133-1153. Published online December 10, 2024; DOI: https://doi.org/10.1007/s12275-024-00180-7

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