Sleep is an evolutionarily conserved behavior found in all animals with a nervous system, ranging from cnidarians to humans. Despite the associated risk to survival, sleep occurs even in organisms with very simple neural networks. Which fundamental functions sleep serves for individual neurons, and why it has become evolutionarily established, remain unresolved.

Recent studies show that sleep enables efficient repair of DNA damage that accumulates during wakefulness. Reactive oxygen species (ROS) play a central role in this process; their levels are influenced both by neuronal activity and by the microbiome. Since nearly all animals host a microbiome, it is plausible that microbial communities were already involved early in evolution in regulating cellular stress as well as sleep and activity rhythms.

The project investigates these relationships using the sea anemone Nematostella vectensis as a model organism, one of the evolutionarily oldest animals with a nervous system. In Nematostella, a circadian clock and sleep-like states have already been described based on genetic and behavioral criteria. In addition, the composition of its microbiome changes over the course of the day.

The project analyzes neuronal activity, ROS levels, and DNA damage and repair processes in living Nematostella animals with high spatial and temporal resolution. Using 3D video tracking and live imaging, wild-type and clock-mutant animals are examined across the day–night cycle, including under targeted sleep manipulations. Complementary metagenomic approaches are used to systematically characterize microbiome dynamics during sleep and wakefulness. Microbiome transplantation experiments are intended to clarify how microbial communities regulate circadian rhythms, cellular stress, and sleep pressure.

The project is designed as an interdisciplinary German–Israeli collaboration, bringing together expertise in molecular neuroscience, marine biology, microbiology, and physical chemistry. In addition to providing new insights into the evolutionary origins of sleep and circadian rhythms, it contributes to a deeper understanding of the fundamental interactions between the nervous system and the microbiome.

The project is funded within the framework of the GIF Nexus Program.