Amphiphiles, Gram-negative bacteria

Polymers having carbohydrate chains linked to a lipid anchor embedded in a bacterial membrane the term bacterial amphiphiles was suggested5 for these polymers. Lipopolysaccharides of Gram-negative bacteria constitute the best-known example of these polymers. 

Neomycin is an aminoglycoside antibiotic which acts as a polycationic amphiphile. It is used in topical creams, ointments, lotions, eye preparations and eardrops, and as an antibacterial preservative agent in some vaccines. Neomycin exhibits exceptional activity against Gram-negative bacteria and also has partial activity against Grampositive bacteria [72],... 

Studies on synthetic oligomers performed by Aisenbrey et al. provided information on the interaction of N-labelled amphiphilic helices with oriented lipid membranes and revealed the antimicrobial nature of these oligomers. Solid-state NMR helped to characterize the structure, dynamics and membrane topology of antimicrobial polypeptides such as alamethicin or p-hairpin antimicrobials,a novel dendrimeric peptide with antimicrobial potency against Gram-negative bacteria and tachyplesin-1, a disulfide stabilized p-hairpin antimicrobial peptide. 

The antibacterial activity of grammistins is a consequence of their amphiphilic a-helical structure. They are active against Gram-positive and Gram-negative bacteria as a consequence of their membrane-lytic activity, but they are not all hemolytic and ichthyotoxic (Yokota, Naga-shima, and Shiomi, 2001 Sugiyama et al, 2005). 

Lipopolysaccharides are heat-stable complex amphiphilic macromolecules indispensable for the bacterial growth, viability and for the correct assembly of the external membrane they represent a defensive barrier which helps bacteria to resist to antimicrobial compounds and environmental stresses and are involved in many aspects of host-bacterium interactions as recognition, adhesion, colonization, and, in the case of extremophile bacteria, in the survival under harsh conditions (Alexander and Rietschel, 2001 Raetz and Whitfield, 2002 Raetz et al 2007). LPS are also called endotoxins because they are cell-bound and, once released, play a key role in the pathogenesis of Gram-negative infections, in mechanisms as... 

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