Effects of Vibrio parahaemolyticus on physiology and metabolism of Thalassiosira weissflogii in the co-culture system.

Diatoms are crucial primary producers in the marine environment, and their interactions with bacteria exert an important role in the ecosystem. There has been scarce research exploring how diatoms adapt to algal-bacterial environments. In this study, we investigated the physiological and transcriptional distinctions of Thalassiosira weissflogii when grown alone (axenic) and with the bacteria Vibrio parahaemolyticus (co-culture). Although the bacteria did not significantly impact the growth of T. weissflogii, they did affect its photosynthetic efficiency and pigment biosynthesis. The balance of carbon and nitrogen metabolism, as well as energy pathways, including the tricarboxylic acid cycle and glycolysis, was also disrupted. T. weissflogii might be capable of maintaining normal growth by upregulating cell cycle-related proteins and utilizing certain bacterial metabolites, such as indole-3-acetic acid. Moreover, T. weissflogii reinforced its cell wall in response to V. parahaemolyticus infection by increasing chitin biosynthesis and inhibiting chitinase activity. This study explored the effects of Vibrio on diatoms from a molecular and metabolic perspective and provided a comprehensive overview of metabolism variations. The results indicate the significant impacts of algal-bacterial interactions on primary producers and offer new insights into the environmental adaptations of diatoms. IMPORTANCE: The significance of this study lies in its contribution to filling the knowledge gap regarding the interactions between diatoms and pathogenic Vibrio. Although extensive research has been conducted on either diatoms or bacteria separately, the mechanisms by which bacteria influence diatom physiological functions and ecosystem processes remain underexplored. Our study reveals that Vibrio can significantly alter diatom photosynthesis efficiency and gene expression patterns, providing new insights into how microbial interactions affect element cycling and primary production in marine ecosystems. These findings may have important implications for marine aquaculture, environmental monitoring, and related fields.