Speaker
Description
Marine phytoplankton is composed of unicellular algae and their associated bacteria. These algal communities are highly variable in species composition, but their patterns tend to recur seasonally. This diversity suggests the existence of ecological niches for the associated bacteria. To clarify the role of the bacterial community on the phytoplankton, we co-cultured several bacterial species with microalgae. We found that the inhibitory or stimulatory function of a particular bacterium depends on both the co-cultured partner and on the different growth phases of the algal culture. Using a generalized Lotka-Volterra model, we were able to predict the behavior of an artificial community composed of C. radiatus diatoms and four bacterial species, and demonstrate the importance of pairwise bacteria-algae interactions. Our study supports the idea that interactions between bacteria and algae are highly species-specific and depend on algal fitness, bacterial metabolism, and community composition. This species specificity may underlie the high complexity of the multi-species plankton communities observed in nature.
