Fig. 2

Host and symbiont diel cycles in diverse marine organisms

(A) Each day at dawn, the majority of the resident Allivibrio fischeri population is expelled from the Euprymna scolopes light organ resulting in low symbiont population density (illustrated by the number of bacteria in the circle). Throughout the day, the remaining symbiont population grows to achieve the necessary density for light production by evening. (B) Epulopiscium sp. type C produce multiple intracellular offspring on a diel cycle. Each morning, the cell divides at each pole. Over the course of the day, the intracellular offspring (forespores) grow. Mature endospores are released from the mother cell prior to sunrise and the spores germinate. The day-night cycle is indicated by a change in background; dark gray indicates night. Forespores are represented by filled in blue ovals and endospores are filled in yellow. Created with BioRender.com.