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Bactoprenol also known as dolichol-11 and (isomerically vaguely) C55-isoprenyl alcohol (C55-OH) is a lipid first identified in certain species of lactobacilli. [1] It is a hydrophobic alcohol that plays a key role in the growth of cell walls ( peptidoglycan ) in Gram-positive bacteria .
Since peptidoglycan is also lacking in L-form bacteria and in mycoplasmas, both are resistant against penicillin. Other steps of peptidoglycan synthesis can also be targeted. The topical antibiotic bacitracin targets the utilization of C55-isoprenyl pyrophosphate. Lantibiotics, which includes the food preservative nisin, attack lipid II. [36]
When a decolorizer such as alcohol or acetone is added, it interacts with the lipids of the cell membrane. [17] A gram-negative cell loses its outer lipopolysaccharide membrane, and the inner peptidoglycan layer is left exposed. The CV–I complexes are washed from the gram-negative cell along with the outer membrane. [18]
Thick peptidoglycan layer; Teichoic acids and lipoids are present, forming lipoteichoic acids, which serve as chelating agents, and also for certain types of adherence. Peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme DD-transpeptidase. A much smaller volume of periplasm than that in gram-negative bacteria.
GlcNAc, a monosaccharide and derivative of glucose, is part of a biopolymer in the bacterial cell wall. This biopolymer forms a layered structure called peptidoglycan (PG). GlcNAc is then converted into GlcNAc-6-P by the enzyme NagE. [10] This substrate is then deacetylated into acetate and GlcN-6-P by NagA. [11]
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Lipid II is then transported across the membrane by a flippase, to expose the disaccharide-pentapeptide monomer, which is the pentapeptide stem consisting of L-Ala-γ-D-Glu-m-DAP-D-Ala-D-Ala between GlcNAc and N-acetylmuramic acid (MurNAc), for polymerization and cross-linking into peptidoglycan. The remaining bactoprenol-pyrophosphate is then ...