Lipid functions in bacterial cell organization

Project Summary/Abstract: Cellular membranes can be organized by the formation of discrete
membrane microdomains (MMs), such as the cholesterol- and flotillin-rich “lipid rafts” found in
eukaryotes. In bacteria, little is understood about the spatial organization of the cell membrane.
Because this domain does not synthesize cholesterol or related eukaryotic lipids, it traditionally
has been assumed that they do not contain raft-like compartments. Hopanoid lipids are the
closest bacterial analogs of cholesterol, and my lab has found that they promote formation of
MMs in the facultative endosymbiont Bradyrhizobium diazoefficiens. These MMs have similar
biophysical properties as eukaryotic lipid rafts and are typically polarized, suggesting a link
between raft-like MMs and cell polarity. Here, I propose to assess whether hopanoid-mediated
MMs have similar compositions as eukaryotic lipid rafts and identify biological processes that
are coordinated in these regions (Project 1). We also will examine cell cycle and polarity
regulation in B. diazoefficiens, and whether it is affected by hopanoid-mediated MMs in both
free-living and host-associated environments (Project 2). These projects will help discover
fundamental paradigms of bacterial membrane organization that are likely to be shared with
human-associated microbes, and may uncover new parallels between bacterial and eukaryotic
subcellular organization.

Grant Number: 5R35GM147015-04
NIH Institute/Center: NIH
Principal Investigator: Brittany Belin