Identification of Lipid Droplets in Gut Microbiota

Summary Recent research has accumulating evidence to support that gut microbiota can be a newly discovered organ/tissue for humans. Although the functions of gut microbiota have been linked to almost all aspects of human physiological, most findings so far are still either belonged to correlational research or at preliminary stage of causal study due to the complexity of gut microbiota as well as lack of proper tools and methods. Thus, development of new approaches is essential and necessary. Lipid droplet is a cellular organelle governing cell lipid homeostasis that is directly related to human metabolic syndromes. Previously we and other groups found lipid droplets in several bacterial strains. We wonder if gut bacteria have lipid droplets. If so, these bacteria may play key roles to regulate gut lipid content, remove unnecessary lipids and produce useful lipid molecules for host. Here we identified lipid droplet-like structures in freshly isolated bacteria from mouse small and large intestines, as well as mouse and human feces. We also purified and analyzed lipid droplets from a cloned human gut bacterium Streptomyces thermovulgaris . Together, we demonstrate the existence of lipid droplets in gut microbiota and established an approach to study them.