The marine alpha-proteobacterium Phaeobacter inhibens engages in intermittent symbioses with microalgae. The symbiosis is biphasic and concludes in a parasitic phase, during which the bacteria release algaecidal metabolites in response to algal p-coumaric acid (pCA). The cell-wide effects of pCA on P. inhibens remain unknown. Herein, we report a microarray-based transcriptomic study and find that genes related to the oxidative stress response and secondary metabolism are upregulated most, while those associated with energy production and motility are downregulated in the presence of pCA. Among genes upregulated is a previously unannotated biosynthetic gene cluster and, using a combination of gene deletions and metabolic profiling, we show that it gives rise to an unreported siderophore, roseobactin. The simultaneous production of algaecides and roseobactin in the parasitic phase allows the bacteria to take up any iron that is released from dying algal cells, thereby securing a limited micronutrient.

海洋 α-变形杆菌Phaeobacter inhibens与微藻间歇性共生。共生是双相的，并在寄生阶段结束，在此期间，细菌响应藻类对香豆酸 (pCA) 释放杀藻代谢物。pCA对P. inhibens的全细胞影响仍然未知。在这里，我们报告了一项基于微阵列的转录组学研究，发现与氧化应激反应和次级代谢相关的基因上调最多，而与能量产生和运动相关的基因在 pCA 存在下下调。在上调的基因中，有一个以前未注释的生物合成基因簇，我们结合基因缺失和代谢谱分析，发现它产生了一种未报道的铁载体roseobactin。在寄生阶段同时产生除藻剂和玫瑰杆菌素使细菌能够吸收垂死的藻类细胞释放的任何铁，从而确保有限的微量营养素。