The outer membrane (OM) of Gram-negative bacteria functions as a protective barrier. It
is unusual because the OM bilayer is asymmetric; the inner leaflet is composed of
phospholipids, but the outer leaflet is made of lipopolysaccharide (LPS). Two kinds of
proteins are found in the OM. Lipoproteins are inserted into the inner leaflet of the OM by
posttranslationally attached lipid moieties. Integral OM proteins are b-barrel proteins
(OMPs). We have used genetic, bioinformatic and biochemical strategies to identify and
characterize the cellular components required for LPS and OMP biogenesis. After
describing what is known about these essential cellular processes, I will focus on the
genetic approaches we are taking to probe the mechanism by which ?-barrel assembly
machine folds and inserts OMPs into the OM. This machine is composed of a large ?-barrel
protein, BamA, and four lipoproteins, Bam BCDE. My talk will focus on the role of BamE
and how the two essential proteins, BamA and BamD communicate with each other.