Coral endosymbiont growth is enhanced by metabolic interactions with bacteria

Bacteria are key contributors to microalgae resource acquisition, competitive performance, and functional diversity, but their functional role when associated with coral microalgal endosymbionts (Symbiodiniaceae) has been largely overlooked. Here, we show that altering the bacterial composition of two widespread Symbiodiniaceae species, during their free-living stage, results in a significant shift in cellular metabolism of the microalgae.