Seminar by Sandeep Krishna

The chemical basis of metabolic interdependence

Sandeep Krishna (NCBS)

Bacterial communities in soil, gut, or marine environments typically consist of many strains, or species, interacting with each other in multiple ways. Cross-feeding, where pairs of species/strains feed off metabolites secreted by the other is an intriguing type of mutual interaction, but not much is known about how prevalent it is in real ecosystems or how beneficial it may or may not be. I will describe how we build an ensemble of randomly assembled metabolic networks that are capable of converting a given set of nutrients to a specified set of biomass precursor molecules. We construct both autonomous networks, as well cross-feeding pairs of networks which can only perform this task successfully in each others' presence. This allows us to compare the energy and biomass yields of the autonomous networks and cross-feeding pairs. We find that some cross-feeding pairs do better than even the best autonomous networks. To understand how this is possible, one needs to understand when it may be beneficial to split a metabolic network into two separate, interacting, compartments. I'll describe the nonlinearities that allow such a split to produce an energy or biomass yield that is different from the merged network, as well as other chemical properties that allow us to predict which cross-feeding pairs do better than autonomous metabolic networks.