Lipid rafts govern cell differentiation in bacteria

The model organism Bacillus subtilis has been used to investigate the ability of bacteria to differentiate into distinct subpopulations of specialized cell types. These subpopulations coexist and collaborate in the development of microbial biofilms. Coordination and interplay between these cell types requires extensive extracellular communication, mostly driven by sensing self-generated secreted signals, in a process commonly referred to as "quorum sensing". Thus, differentiation of cell types in microbial populations highly depends on bacteria`s ability to perceive the presence of signaling molecules. Precisely, Lopez and coworkers have recently discovered specific areas in the membrane of bacteria which recruit the proteins required to sense and to respond to several differentiation signals. These membrane microdomains are similar in function to the so-called "lipid rafts" in eukaryotic cells. The integrity of these areas affects processes related to cell-cell communication, cellular differentiation and cell cycle in bacteria. We will use a variety of genetic and biochemical approaches to study in detail the molecular mechanisms controlled by lipid rafts in B. subtilis and how they govern cell differentiation in microbial communities. We will investigate how lipid rafts regulate the activation of the genetic cascades that lead to cell differentiation and how bacteria benefit from the compartmentalization of these pathways in membrane microdomains. We will explore the role of a specific protein that localizes exclusively in lipid rafts, named Flotillin-1. In eukaryotes, Flotillin-1 coordinates the diverse functions within the rafts, thus we think Flotillin-1 might regulate a large number of signaling pathways in bacterial lipid rafts as well. Key experiments using B. subtilis as working model will be reproduced in the model Staphylococcus aureus, to visualize how the organization of lipid rafts varies among different bacterial species.