AUTHOR=Cho Suhyung , Cho Sang-Hyeok , Ko So-Ra , Jeong Yujin , Lee Eunju , Jin Sangrak , Jeong Bo-Seong , Oh Byung-Ha , Oh Hee-Mock , Ahn Chi-Yong , Cho Byung-Kwan 

TITLE=Elucidation of the Algicidal Mechanism of the Marine Bacterium Pseudoruegeria sp. M32A2M Against the Harmful Alga Alexandrium catenella Based on Time-Course Transcriptome Analysis

JOURNAL=Frontiers in Marine Science

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2021.728890

DOI=10.3389/fmars.2021.728890

ISSN=2296-7745

ABSTRACT=<p>The marine dinoflagellate <italic>Alexandrium</italic> is associated with harmful algal blooms (HABs) worldwide, causing paralytic shellfish poisoning (PSP) in humans. We found that the marine bacterium <italic>Pseudoruegeria</italic> sp. M32A2M exhibits algicidal activity against <italic>Alexandrium catenella</italic> (Group I), inhibiting its motility and consequently inducing cell disruption after 24 h of co-culture. To understand the communication between the two organisms, we investigated the time-course cellular responses through genome-wide transcriptome analysis. Functional analysis of differentially expressed genes revealed that the core reactions of the photosystem in <italic>A. catenella</italic> were inhibited within 2 h, eventually downregulating the entire pathways of oxidative phosphorylation and carbon fixation, as well as associated metabolic pathways. Conversely, <italic>Pseudoruegeria</italic> upregulated its glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation pathways. Also, the transporters for nutrients such as C3/C4 carbohydrates and peptides were highly upregulated, leading to the speculation that nutrients released by disrupted <italic>A. catenella</italic> cells affect the central metabolism of <italic>Pseudoruegeria</italic>. In addition, we analyzed the secondary metabolite-synthesizing clusters of <italic>Pseudoruegeria</italic> that were upregulated by co-culture, suggesting their potential roles in algicidal activity. Our time-course transcriptome analysis elucidates how <italic>A. catenella</italic> is affected by algicidal bacteria and how these bacteria obtain functional benefits through metabolic pathways.</p>