Bacterial outer membrane polymers

In bacterial lipopolysaccharides, O-specific chains composed of repeating, or modified repeating, units are linked to a unique oligosaccharide sequence of the core region which is connected to a lipid A fragment serving as a hydrophobic anchor embedded in the bacterial outer-membrane. Biosynthesis of O-specific chains was found to occur independently on formation of other structural fragments of the lipopolysaccharide molecule. Both block and monomeric mechanisms were demonstrated for the biosynthesis of these polymers. 

Bacterial cells share certain common structural features, but also show group-specific specializations (Fig. 1-6). E. coli is a usually harmless inhabitant of the human intestinal tract. The E. coli cell is about 2 prri long and a little less than 1 prri in diameter. It has a protective outer membrane and an inner plasma membrane that encloses the cytoplasm and the nucleoid. Between the inner and outer membranes is a thin but strong layer of polymers called peptidoglycans, which gives the cell its shape and rigidity. The plasma membrane and the... 

The polymer efficiently permeabilises anionic vesicles with compositions which mimic those of bacterial membranes. The polymer binds to anionic phospholipid vesicles but not zwitterionic vesicles, which causes phase separation in anionic phospholipid mixtures, clustering the negative charge. The polymer permeabilises the outer membrane of Escherichia coli ML-35p in a biphasic manner low polymer concentrations permeabilise the inner membrane of Escherichia coli ML-35p, whereas high concentrations of the polymer can block the active transport of or onitrophenyl-P-n-galactoside in wild-type Escherichia coli K12 [17]. 

Figure 1 Schematic illustration of the supramolecular architecture of the three major classes of prokaryotic cell envelopes containing crystalline bacterial cell surtece layers (S-layers). (a) Cell envelope structure of Gram-negative archaea with S-layers as the only cell wall component external to the cytoplasmic membrane, (b) Cell envelope as observed in Gram-positive archaea and bacteria. In bacteria the rigid wall component is primarily composed of peptidoglycan. In archaea other wall polymers (e.g., pseudomurein or methanochondroitin) are found, (c) Cell envelope profile of Gram-negative bacteria, composed of a thin peptidoglycan layer and an outer membrane. If present the S-layer is closely associated with the lipopolysaccharide of the outer membrane. (Modified after U.B. Sleytr, P. Messner, D. Pum, and M. Sdra. Crystalline Bacterial Cell Surface Proteins. Austin, TX R.G. Landes/Academic Press, 1996. With permission.)...

Biodegradable polymers accelerate the degradation of bacteria or pathogens due to the hydrophilic backbone chain of polymers which contain atoms, such as O, N, S, in the polymer chain. The amorphous nature, small size and high porosity of biodegradable polymers are the factors which disrupt the outer bacterial membrane. 

---