The complexity of a microbiome is daunting. A human gut microbiome may have over 1,000 individual species of bacteria that co-exist stably over years or possibly over generations. We lack an understanding of the forces that contribute to this surprising stability. In this workshop, we will dive in and examine stripped down systems to test hypotheses on how the simplest microbiomes are defined and what mechanisms they use to remain stable. The example of the circadian clock − the biological timekeeping mechanism that sculpts our inner day − will be invoked to explore how a regular, systematic, daily stimulus shapes the composition of the gut microbiome of the mouse over the course of a day. | The keynote lecturer Javier A. Ceja-Navarro is Associate Professor for Biological Systems and Engineering at Lawrence Berkeley National Laboratory.

Microbial ecology tries to adapt theories from general ecology into the microbial world to describe general principles of microbiomes on earth related to self-organization as well as resilience or functional redundancy. Microbial ecology aims to improve our understanding of the interactions of microorganisms with their environment, each other, and plant and animal species. It includes the study of symbioses, biogeochemical cycles and the interaction of microbes with anthropogenic effects such as pollution and climate change. Ecosystems of interest include natural environments, managed and technical ecosystems, extreme environments, as well as humans, animals and plants.

The existence of brain gut microbiome interactions and the role of alterations in this regulatory system has clearly been established in a series of mouse models for anxiety, depression, autism spectrum disorders, Parkinson’s disease and multiple sclerosis. Recent studies have demonstrated that fecal transplant from human disease populations into gnotobiotic mice, can induce behavioral changes in these animals. However, definitive evidence for a causal role of the gut microbiome in human brain dysfunction remains to be established. Based on cross sectional studies, Emeran Mayer provides evidence for associations between gut microbial composition, brain parameters and behavioral measures in humans. Additionally, he demonstrates correlations between gut microbial architecture and function, food cravings and brain parameters in obesity and in irritable bowel syndrome. | Emeran A. Mayer ist Professor am Department für Medizin, Physiologie und Psychiatrie an der David Geffen School of Medicine, UCLA und derzeit Visiting Fellow am CAS.