Bacterial cell membranes bacteria

Bacitracin is a bactericidal drug that inhibits the formation of linear peptidoglycan chains, which are the main component of bacterial cell membranes. Most Gram-positive bacteria,... 

The polymyxins are a group of basic peptides active against gram-negative bacteria and include polymyxin and polymyxin E (colistin). Polymyxins act like cationic detergents. They attach to and disrupt bacterial cell membranes. They also bind and inactivate endotoxin. Gram-positive organisms, proteus, and neisseria are resistant. 

Polymyxin B. Polymyxin antibiotics are cationic compounds that are attracted to negatively charged phospholipids in the bacterial cell membrane. These drugs penetrate and disrupt the architecture and integrity of the surface membrane. Essentially, polymyxins act as detergents that break apart the phospholipid bilayer, which creates gaps in the bacterial cell wall, leading to the subsequent destruction of the bacteria.31... 

Branched-chain fatty acids (BrFAs) (iso- and anteiso) are believed to be primarily derived from sulfate-reducing bacteria (Perry et al., 1979 Cranwell, 1982 Canuel et al., 1995 table 9.5). However, it should be noted that BrFAs are not present in all sulfate-reducing bacteria or other heterotrophic bacteria (Kaneda, 1991 Kohring et al., 1994). The iso- and antesio- designation represents a branched fatty acid with the methyl group at the a>-l position and the methyl group at the a>-2 position, respectively. The odd number (C45, C17, branched and normal) are believed to be derived from phospholipids, components of bacterial cell membranes (Kaneda, 1991). Even-numbered iso-branched fatty acids (e.g., C12—Cig) are also found in algal sources (Schnitzer and Khan, 1972). 

Menaquinones are absorbed mainly from the terminal ileum, where bile salts are present, into the hepatic portal vein. Litde of the menaquinones formed by colonic bacteria can be absorbed, because they remain tightly bound to bacterial cell membranes in the absence of bile salts. About 90% of the total liver content of vitamin K is menaquinones 7 to 13, and the hepatic pool of phylloquinone turns over considerably faster than that of menaquinones. Sixty percent to 70% of the daily intake of phylloquinone is excreted, mainly as conjugates in the bile, and the half-life of a tracer dose of phylloquinone is only about 17 hours. 

Scientists at MIT and Tufts University have demonstrated that covalent attachment of N-alkylated poly (4-vittylpy ridine) (PVP) to glass surfaces makes the surfaces lethal to several types of bacteria on contact. PVP and other polycationic polymers in solution can kill bacteria by dismpting bacterial cell membranes. The scientists have found a fairly narrow range of N-alkylated PVP compositions that allow the polymers to retain their bacteria-killing ability when coated on dry surfaces. The group hopes to demonstrate that any common surface, whether its PVC, PE, metals, ceramics, wood or fabrics, can use this kind of derivatisation to make that surface capable of killing airborne bacteria. 

Nisin acts bactericidally primarily against gram-positive bacteria. It acts best at acid pH and is almost insoluble at physiological pH. Nisin and probably all lantibiotics appear to permeabilize the bacterial cell membrane to release small molecules, resulting in an immediate collapse of the membrane... 

The physiological role for the conversion of chenodeoxychoUc acid to ursodeoxycholic acid by C. absonum or other intestinal bacteria is unknown. However, ursodeoxychoUc acid is more polar than chenodeoxycholic acid (Chapter 13) and should be less toxic to bacterial cell membranes than the latter. Indeed, C. absonum will readily grow in media containing 1 mM ursodeoxychoUc acid but not 1 mM chenodeoxychoUc acid [42]. Therefore, the epimerization of the axial 7 -hydroxyl group may represent a detoxication process for C. absonum and would provide a physiological explanation for these enzymes. 

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