Abstract

Co-authors: Katherine Helliwell (University of Cambridge), Elena Kazamia (University of Cambridge), Matthew Cooper (University of Cambridge), Vaibhav Bhardwaj (University of Cambridge), Christian Ridley (University of Cambridge), Johan Kudahl (University of Cambridge)

Over half of all microalgae require an external source of vitamins, particularly vitamin B12 (cobalamin), to enable them to grow. There is no phylogenetic relationship between those that require the vitamin and those that do not. Bacteria are the only organisms that can synthesise this complex organic micronutrient, and we have shown that B12 -dependent algae can grow in co-culture with bacteria that supply them the vitamin in exchange for fixed carbon. We have established a model system to study this interaction at the molecular level, and to explore reasons for why vitamin auxotrophy may have arisen so frequently across the diverse algal lineages. This may provide insights into the evolution of mutualism between algae and their bacterial partners.