The interaction between marine phyto- and bacterioplankton is regulated by multiple environmental and biological factors. Among them, phages as the major regulators of bacterial mortality are considered to have important impacts on algae-associated bacteria and algae-bacteria relationship. However, little is currently known about the actual impact of phages from this perspective. Here, we revealed that phage infection improved the maximum quantum efficiency of photosystem II of Phaeodactylum tricornutum by regulating the associated bacterial community. Specifically, phage infection weakened bacterial abundance and eliminated their negative effects on the diatom. Unexpectedly, the structure of the bacterial community co-cultured with the diatom was not significantly affected, likely because the shaping effect of the diatom on the bacterial community structure can far outcompete or mask the impact of phage infection. Our results established a link between algae, bacteria, and phages, suggesting that phage infection benefits the diatom by regulating the associated bacterial community.

海洋浮游植物和细菌之间的相互作用受到多种环境和生物因素的调节。其中，噬菌体作为细菌死亡率的主要调节因子，被认为对藻类相关细菌以及藻菌关系具有重要影响。然而，目前人们对噬菌体从这个角度的实际影响知之甚少。在这里，我们发现噬菌体感染提高了三角褐指藻光系统II的最大量子效率通过调节相关的细菌群落。具体来说，噬菌体感染削弱了细菌丰度并消除了它们对硅藻的负面影响。出乎意料的是，与硅藻共培养的细菌群落结构并未受到显着影响，这可能是因为硅藻对细菌群落结构的塑造作用可以远远超过或掩盖噬菌体感染的影响。我们的结果建立了藻类、细菌和噬菌体之间的联系，表明噬菌体感染通过调节相关的细菌群落对硅藻有益。