2-Structure_and_Function_Jan15-17

It is so dense that it is someames called a protein

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Unformatted text preview: covalently to the pepAdoglycan by an enzyme called sortase. Teichoic acid 42 Brock Biology of Microorganisms, 13th EdiAon. Cell wall of Gram- negaAve bacteria 43 Brock Biology of Microorganisms, 13th EdiAon. Cell wall of Gram- negaAve bacteria •  PepAdoglycan: 5- 10% of the cell wall. •  The pepAdoglycan is located in the periplasm, the space delimited by the cytoplasmic membrane and the outer membrane. The periplasm contains a high concentraAon of proteins involved in diverse of funcAons, such as nutrient acquisiAon, extracellular enzymaAc reacAons, sensing, etc. It is so dense that it is someAmes called a “protein gel”. •  The outer membrane is an atypical lipid bilayer: phospholipids in the inside layer, phospholipids and lipopolysaccharide in the outside layer (LPS layer). •  The LPS helps protect the bacteria against a variety of substances, including anAbioAcs, and against the host defense system. •  The outer membrane also contains outer membrane proteins (OMPs), such as porins, and lipoproteins which play a structural role. 44 LPS of Gram- negaAve bacteria •  LPS is a family of complex sugar polymers abached to a lipid moiety known as lipid A. Lipid A is toxic to many animals, it can cause acute inflammaAon and vascular problems (sepAc shock) that can result in death. Lipid A is an endotoxin and it plays a major role in the pathogenesis of Gram- negaAve bacterial pathogens. Lipid A contains 6 lipid tails that are embedded in the membrane. KDO: 2- keto- deoxyoctonate, links the lipid A to the polysaccharide chain. •  O- specific polysaccharide, also known as the O anAgen, consists of repeaAng sequences of 2- 4 monosaccharides. Huge diversity of O anAgens so it can be used to idenAfy different strains of one species of bacteria: ex: E. coli O157:H7 (O157 serogroup). 45 Brock Biology of Microorganisms, 13th EdiAon....
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