Osmotic stress in viable Escherichia coli as the basis for the antibiotic response by polymyxin B |
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Authors: | JT Oh TK Van Dyk Y Cajal PS Dhurjati M Sasser MK Jain |
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Affiliation: | Department of Chemistry, University of Delaware, Newark 19716, USA. |
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Abstract: | Cationic antimicrobial peptides, such as polymyxin B (PxB), below growth inhibitory concentration induce expression of osmY gene in viable E. coli without leakage of solutes and protons. osmY expression is also a locus of hyperosmotic stress response induced by common food preservatives, such as hypertonic NaCl or sucrose. High selectivity of PxB against Gram-negative organisms and the basis for the hyperosmotic stress response at sublethal PxB concentrations is attributed to PxB-induced mixing of anionic phospholipid between the outer layer of the cytoplasmic membrane with phospholipids in the inner layer of the outer membrane. This explanation is supported by PxB-mediated rapid and direct exchange of anionic phospholipid between vesicles. This mechanism is consistent with the observation that genetically stable resistance against PxB could not be induced by mutagenesis. |
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