Phytoplankton are primarily confined to the sunlit epipelagic zone, yet intact algal cells persist in the ocean’s mesopelagic twilight zone where light is minimal. However, their survival strategies in the deeper ocean remain unknown. Here, we isolate Chaetoceros sp. DS1 from 1000 m depth and reveal its survival mechanisms under prolonged darkness and high pressure, including membrane lipid remodeling and enhanced antioxidant defenses. Importantly, DS1 maintains a latent photosynthetic reserve that activates upon exposure to dim blue light and higher pressure typical of the twilight zone, enabling photosynthesis and nutrient uptake. It exhibits metabolic flexibility by utilizing stored carbon in darkness and assimilating organic carbon under dim light. Global meta-omics data show widespread, transcriptionally active Chaetoceros-like diatoms in the twilight zone, expressing blue-light sensors and protein synthesis genes. These findings identify the ocean twilight zone as a previously overlooked niche for metabolically active phytoplankton, expanding understanding of deep-ocean microbial ecology and carbon cycling.
ABSTRACT Vibrio sinaloensis has been reported in association with disease events in aquaculture, yet its genomic features and non-antibiotic suppression strategies remain largely unexplored. Here, we report genomic characterization of a multidrug-resistant V. sinaloensis strain, ZZ006, isolated from diseased shrimp and evaluate phage-mediated suppression of this strain in vitro. The ZZ006 genome harbors multiple putative virulence-associated secretion systems and antimicrobial resistance genes, suggesting chromosomal carriage of traits potentially relevant to host association and antimicrobial tolerance. Using this isolate and its phage-resistant derivatives as hosts, we isolated and characterized three novel bacteriophages (VS1, VS2, VS3) with complementary infection strategies. Their combined application efficiently suppressed ZZ006 growth in vitro and reduced the emergence of phage-resistant populations compared with individual phages. Whole-genome resequencing of cocktail-resistant isolates revealed recurrent mutations in pilus- and pseudopilin-associated genes, consistent with receptor-level phage resistance. This study provides genomic characterization of an aquaculture-associated V. sinaloensis isolate and establishes an in vitro framework for phage cocktail suppression and resistance-evolution analysis, supporting future evaluation of phage-based biocontrol in aquaculture-relevant settings. IMPORTANCE Vibrio sinaloensis has been detected in diseased aquaculture animals, and multidrug-resistant isolates may complicate disease management. By integrating genomic analysis with experimental phage therapy, this work characterizes a multidrug-resistant V. sinaloensis isolate from diseased shrimp and evaluates in vitro phage-mediated suppression of this isolate and its phage-resistance evolution. These findings offer actionable solutions for mitigating antibiotic resistance and enhancing sustainability in aquaculture systems. Vibrio sinaloensis has been detected in diseased aquaculture animals, and multidrug-resistant isolates may complicate disease management. By integrating genomic analysis with experimental phage therapy, this work characterizes a multidrug-resistant V. sinaloensis isolate from diseased shrimp and evaluates in vitro phage-mediated suppression of this isolate and its phage-resistance evolution. These findings offer actionable solutions for mitigating antibiotic resistance and enhancing sustainability in aquaculture systems.
Zhongfeixue Wang, Jiulong Zhao, Chengcheng Li et al.· Applied and Environmental Mi...· 0 citations
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