Genomic analysis of Vibrio fluvialis QY27 related to its deep-sea environment adaptation

Vibrio fluvialis QY27, isolated from 2,500 m deep seawater in the South China Sea, was previously shown to tolerate high pressure via trimethylamine-N-oxide metabolism. However, the comprehensive adaptive mechanisms underlying its adaptation to the deep-sea environment remained poorly understood. To better understand its deep-sea adaptation, we conducted genomic and functional analyses. The complete genome comprises two circular chromosomes (4.78 Mb, 49.99 % GC), encoding 4,265 proteins, 108 tRNAs, and 31 rRNAs. Phylogenetically, QY27 shares 98.51 % ANI with V. fluvialis ATCC33809 and possesses a unique set of accessory and rare genes, reflecting significant genomic plasticity. Key adaptive features of QY27 is underpinned by key systems for essential resource acquisition: a multifaceted iron uptake system (vibriobactin, Feo, Efe), diverse terminal oxidases (bd, cbb₃, aa₃, bo₃) for aerobic flexibility, and integrated nitrogen metabolism pathways (TMAO respiration via torCAD/YZ and assimilatory nitrate reduction via napAB-nirBD). These integrated systems create a synergistic network, enabling QY27 to overcome high pressure, oxygen limitation, and nutrient scarcity in the deep sea. This study provides systematic insights into the metabolic adaptation of a non-piezophilic Vibrio fluvialis, advancing our understanding of microbial ecological adaptation and evolutionary in extreme environments.