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=Volume 8 - 2021

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=The marine dinoflagellate Alexandrium is associated with harmful algal blooms (HABs) worldwide, causing paralytic shellfish poisoning in humans. We found that the marine bacterium Pseudoruegeria sp. exhibits algicidal activity against Alexandrium catenella (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 A. catenella were inhibited within 2 h, eventually downregulating the entire pathways of oxidative phosphorylation and carbon fixation, as well as associated metabolic pathways. Meanwhile, the glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation pathways were activated in Pseudoruegeria sp. The transporters for nutrients such as C3/C4 carbohydrates and peptides were highly upregulated in Pseudoruegeria sp., leading to the speculation that nutrients released by disrupted A. catenella cells are taken up by Pseudoruegeria sp. and that central metabolism is activated. In addition, we analyzed the secondary metabolite-synthesizing clusters of Pseudoruegeria sp. that were upregulated by co-culture, suggesting their potential roles in algicidal activity. Our time-course transcriptome analysis elucidates how A. catenella is affected by algicidal bacteria and how these bacteria obtain functional benefits through metabolic pathways.