Temporal variability of microbiome in the different plankton hosts revealed distinct environmental persistence of Vibrio parahaemolyticus in shrimp farms

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.

Noctiluca scintillans bloom alters the composition and carbohydrate utilization of associated bacterial community and enriches potential pathogenic bacterium Vibrio anguillarum

Noctiluca scintillans (red) is a widely distributed heterotrophic dinoflagellate and a prominent red tide forming species. This study investigated the effects of Noctiluca blooms on marine microbial diversity and functionality using multi-omics approaches. Our findings revealed significant differences in the community composition of Noctiluca-associated bacteria compared to those associated with autotrophic plankton and free-living bacteria in the surrounding seawater. The dominant bacterial groups within the Noctiluca-associated community shifted at various bloom stages, which could be attributed to changes in prey composition of Noctiluca. During the non-bloom stage, Burkholderiaceae, Carnobacteriaceae, and Pseudomonadaceae dominated the community, while Vibrionaceae became dominant during the bloom stage, and Saprospiraceae, Crocinitomicaceae, and Pirellulaceae thrived during the post-bloom stage. Compared to the non-bloom stage, Noctiluca-associated bacterial community at the bloom stage exhibited significant down-regulation of genes related to complex carbohydrate metabolism, while up-regulation of genes related to glucose transportation and utilization. Furthermore, we identified Vibrio anguillarum, a potential pathogenic bacterium to marine fish, as a major component of the Vibrionaceae family during the bloom stage. The occurrence of V. anguillarum associated with Noctiluca blooms may be attributed to the increased availability of its preferred carbon sources and its high capabilities in glucose transportation, motility and chemotaxis. Moreover, the presence of Vibrio infection genes (hap, hlyA, rtxA) encoding vibriolysin, hemolysin, and RTX (Repeats-in-toxin) toxin in the V. anguillarum genome, with the hap gene showing high expression levels during Noctiluca blooms, indicates an elevated risk of infection. This study underscores the unique composition of the bacterial community associated with red tide forming heterotrophic dinoflagellates and suggests that Noctiluca cells may serve as reservoirs and vectors for pathogenic bacteria, potentially posing a threat to fish-farming and the health of other marine organisms.