Briand Enora, Lassudrie Malwenn, Bérard Jean-Baptiste, Jauzein Cécile, Labry Claire, Lacour Thomas, Nef Charlotte, Noël Cyril, Raimbault Virginie, Schreiber Nathalie, Sibat Manoëlla, Tanniou Simon, Réveillon Damien, Garnier Matthieu
IFREMER, PHYTOX, GENALG, Nantes, France.
IFREMER, COAST, LER BO, Paris, France.
Environ Microbiol. 2025 Jul;27(7):e70150. doi: 10.1111/1462-2920.70150.
In this study, we examined the role of species-specific algal exudates in shaping bacterial community structure and interactions using synthetic microbial communities co-cultured with Alexandrium minutum and Prymnesium parvum. Cell-free algal exudates supported bacterial growth as the sole carbon source and revealed distinct exometabolomes unique to each algal species. These exometabolomes selectively influenced bacterial community composition, even among common copiotrophic taxa. Furthermore, co-culture experiments highlighted that the presence of algal cells drove further bacterial assembly, particularly within particle-attached communities, emphasising the role of close algal-bacterial interactions in structuring microbial consortia. Metabolomic analyses showed significant modulation of algal exudates by bacteria, with axenic cultures containing a broader and more diverse range of metabolites. This suggests microbial consumption, degradation or suppression of metabolite production under xenic conditions. Importantly, we observed a bacterial-mediated increase in extracellular paralytic shellfish toxins (PSTs) in A. minutum cultures. Exudates of both algal species displayed hemolytic activity, which was not affected by the presence of bacteria, suggesting bioactive extracellular compounds (BECs) production does not rely on bacteria. These findings underscore the complex and dynamic nature of algal-bacterial interactions, with implications for nutrient cycling, toxin dynamics and harmful algal bloom ecology.
在本研究中，我们使用与微小亚历山大藻（Alexandrium minutum）和微小原甲藻（Prymnesium parvum）共培养的合成微生物群落，研究了物种特异性藻类分泌物在塑造细菌群落结构和相互作用中的作用。无细胞藻类分泌物作为唯一碳源支持细菌生长，并揭示了每种藻类特有的独特胞外代谢组。这些胞外代谢组选择性地影响细菌群落组成，即使在常见的富营养类群中也是如此。此外，共培养实验强调藻类细胞的存在推动了进一步的细菌组装，特别是在附着于颗粒的群落中，这突出了紧密的藻菌相互作用在构建微生物聚集体中的作用。代谢组学分析表明细菌对藻类分泌物有显著调节作用，无菌培养物含有更广泛和更多样化的代谢物。这表明在混合培养条件下微生物对代谢物的消耗、降解或代谢物产生的抑制。重要的是，我们观察到在微小亚历山大藻培养物中细菌介导的细胞外麻痹性贝类毒素（PSTs）增加。两种藻类的分泌物均表现出溶血活性，这不受细菌存在的影响，表明生物活性胞外化合物（BECs）的产生不依赖于细菌。这些发现强调了藻菌相互作用的复杂和动态性质，对营养物质循环、毒素动态和有害藻华生态学具有重要意义。
