Kadriye Toklu

Aquaculture environments are dynamic ecosystems that may influence the evolution and adaptive potential of bacterial pathogens. In this study, a locally isolated Vibrio anguillarum strain VK1 (PRJNA1452808) from Türkiye was characterized using 16S rDNA phylogenetic analysis and whole-genome-based approaches. The high-quality draft genome (4.23 Mb; GC content 44.31%) comprised 194 contigs and 4,102 coding sequences, including 1,057 hypothetical proteins. Functional analyses revealed putative stress response mechanisms and iron acquisition systems, suggesting metabolic versatility and environmental adaptability. Genome-based screening identified 33 putative antimicrobial resistance-associated determinants, including multidrug efflux-related genes and genes linked to antibiotics commonly used in aquaculture. In addition, genes associated with Type III and Type VI secretion systems were detected, potentially indicating adaptive traits related to host interaction and environmental persistence. Overall, the findings suggest that strain VK1 possesses a flexible genomic structure that may support adaptation to fluctuating aquaculture conditions. However, further functional studies are needed to biologically validate the potential virulence and AMR related features.

The Gram-negative marine bacterium Photobacterium damselae subsp. piscicida (Pdp) is a pathogen responsible for pseudotuberculosis in various fish species, posing significant threats to aquaculture. Pdp employs strong virulence mechanisms, one of which is the production of the piscibactin siderophore, which plays a key role in iron acquisition from the host. In this study, we evaluated the ferrophilic properties of the Pdp strain EKL1 in relation to growth and biofilm production. In vitro iron limitation significantly suppressed biofilm formation and planktonic growth in EKL1. We then investigated the anti-biofilm activity of deferoxamine (DFO), an iron chelator used to treat transfusion-induced iron overload in thalassemia patients, against EKL1. DFO strongly inhibited EKL1 biofilm production (by 82.1%), suggesting that iron chelation therapy could be an effective strategy to prevent Pdp-induced photobacteriosis outbreaks. Finally, we characterized the iron-bound form of piscibactin through extensive spectroscopic analyses of the siderophore produced by EKL1. Our findings contribute to the development of novel piscibactin-targeted inhibitors, advancing siderophore-based anti-virulence strategies against Pdp.