Changes in interactions over ecological time scales influence single cell growth dynamics in a metabolically coupled marine microbial community

Abstract

Microbial communities thrive in almost all habitats on earth. Within these communities, cells interact through the release and uptake of metabolites. These interactions can have synergistic or antagonistic effects on individual community members. The collective metabolic activity of microbial communities leads to changes in their local environment. As the environment changes over time, the nature of the interactions between cells can change. We currently lack understanding of how such dynamic feedbacks affect the growth dynamics of individual microbes and of the community as a whole. Here we study how interactions mediated by the exchange of metabolites through the environment change over time within a simple marine microbial community. We used a microfluidic-based approach that allows us to disentangle the effect cells have on their environment from how they respond to their environment. We found that the interactions between two species - a degrader of chitin and a cross-feeder that consumes metabolic by-products - changes dynamically over time as cells modify their environment. Cells initially interact positively and then start to compete at later stages of growth. Our results demonstrate that interactions between microbes are not static and depend on the state of the environment, emphasizing the importance of disentangling how modifications of the environment affects species interactions. This experimental approach can shed new light on how interspecies interactions scale up to community level processes in natural environments.

Effects of interspecies interactions on marine community ecosystem function

“…To study this, we used degrader-cross-feeder co-cultures involving Neptunomonas and Alteromonas strains. The individual interactions between Neptunomonas and V. splendidus and Alteromonas and V. natriegens strains have previously been studied in detail (28, 29). These studies revealed that both the Alteromonas and Neptunomonas strain were cross-feeders in the sense that they are unable to degrade chitin or consume primary degradation products such as mono- or dimers and instead rely on metabolic by-products excreted by the degraders, such as acetate for carbon sources.…”