Dry-Heating of Lysozyme Increases Its Activity against Escherichia coli Membranes

• Published in: Journal of agricultural and food chemistry Vol. 62; no. 7; pp. 1692 - 1700
• Main Authors: Derde, Melanie, Guérin-Dubiard, Catherine, Lechevalier, Valérie, Cochet, Marie-Françoise, Jan, Sophie, Baron, Florence, Gautier, Michel, Vié, Véronique, Nau, Françoise
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 19-02-2014; American Chemical Society, Books and Journals Division
• Subjects: Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - pharmacology; anti-infective properties; atomic force microscopy; Biochemistry, Molecular Biology; Biophysics; Cell Membrane Permeability - drug effects; Condensed Matter; Escherichia coli; Escherichia coli - drug effects; Gram-negative bacteria; Gram-positive bacteria; hydrophobicity; ion channels; Life Sciences; lysozyme; microbial growth; Microbial Sensitivity Tests; Muramidase - chemistry; Muramidase - pharmacology; Physics; population dynamics; Protein Stability; Soft Condensed Matter; lysozyme; antimicrobial activity; Gram-negative bacteria; dry-heating; membrane disruptions
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf405155p

For food as well as for medical applications, there is a growing interest in novel and natural antimicrobial molecules. Lysozyme is a promising candidate for the development of such molecules. This protein is largely studied and known for its muramidase activity against Gram-positive bacteria, but it also shows antimicrobial activity against Gram-negative bacteria, especially when previously modified. In this study, the activity of dry-heated lysozyme (DH-L) against Escherichia coli has been investigated and compared to that of native lysozyme (N-L). Whereas N-L only delays bacterial growth, DH-L causes an early-stage population decrease. The accompanying membrane permeabilization suggests that DH-L induces either larger pores or more pores in the outer membrane as compared to N-L, as well as more ion channels in the inner membrane. The strong morphological modifications observed by optical microscopy and atomic force microscopy when E. coli cells are treated with DH-L are consistent with the suggested disturbances of membrane integrity. The higher hydrophobicity, surface activity, and positive charge induced by dry-heating could be responsible for the increased activity of DH-L on the E. coli membranes.