Growth of in Defined Media Is Dependent on Presence of Particulate Matter.

are typically cultured in a monoxenic medium consisting of live bacteria. However, this introduces a secondary organism to experiments, and restricts the manipulation of the nutritional environment. Due to the intricate link between genes and environment, greater control and understanding of nutritional factors are required to push the field into new areas. For decades, attempts to develop a chemically defined, axenic medium as an alternative for culturing have been made. However, the mechanism by which the filter feeder obtains nutrients from these liquid media is not known. Using a fluorescence-activated cell sorting based approach, we demonstrate growth in all past axenic media to be dependent on the presence of previously unknown particles. This particle requirement of led to development of liposome-based, nanoparticle culturing that allows full control of nutrients delivered to .