Microalgae have a crucial role in primary production, influencing the dynamic of their ecosystem through interaction with other microorganisms. Despite their importance, the precise nature of these interactions remains poorly understood. Carrasco Flores et al. have previously demonstrated that the soil bacterium Pseudomonas protegens inhibits the growth of the green microalga Chlamydomonas reinhardtii by releasing secondary metabolites that deflagellate and lyse the algae. In this study, the authors report a third interaction partner, Mycetocola lacteus, a Gram-positive actinomyces bacterium. Interestingly, M. lacteus rescues the algal cells from the activity of P. protegens by cleaving and therefore inactivating the toxic cyclic lipopeptide orfamide A produced by P. protegens. The interaction between M. lacteus and the algae is not only beneficial for the algae but also for M. lacteus; the algae provide essential nutrients such as vitamin B and methionine, promoting the growth of M. lacteus in return. Therefore, a mutualistic partnership that benefits both is established.

In sum, this study underscores the complexity of microbial interactions and their ecological relevance. Further exploration of such interactions and the underlying metabolites involved is key to understanding the vital role of microorganisms in sustaining life on Earth.