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Dry-heating of lysozyme increases its activity against Escherichia coli membranes
Melanie Derde1, Catherine Guérin-Dubiard, Valérie Lechevalier
1Agrocampus Ouest, UMR1253 Science et technologie du lait et de l'œuf , F-35042 Rennes, France.
Abstract:
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.
Insights
Dry-heated lysozyme (DH-L) shows enhanced antimicrobial activity against E. coli compared to native lysozyme (N-L). DH-L disrupts bacterial membranes, causing significant population decrease and morphological changes, making it a promising natural antimicrobial agent.
Area of Science:
- Microbiology
- Biochemistry
- Food Science
Background:
- Growing demand for natural antimicrobial molecules in food and medicine.
- Lysozyme is a known antimicrobial protein with muramidase activity against Gram-positive bacteria.
- Modified lysozyme exhibits enhanced antimicrobial properties, particularly against Gram-negative bacteria.
Purpose of the Study:
- To investigate the antimicrobial activity of dry-heated lysozyme (DH-L) against Escherichia coli.
- To compare the efficacy of DH-L with native lysozyme (N-L).
- To elucidate the mechanisms behind DH-L's enhanced antimicrobial action.
Main Methods:
- Treatment of E. coli with native lysozyme (N-L) and dry-heated lysozyme (DH-L).
- Assessment of bacterial growth and population changes.
- Analysis of membrane permeabilization and integrity using optical microscopy and atomic force microscopy.
- Evaluation of biophysical properties such as hydrophobicity and charge.
Main Results:
- Native lysozyme (N-L) only delayed E. coli growth.
- Dry-heated lysozyme (DH-L) induced an early-stage population decrease in E. coli.
- DH-L caused significant membrane permeabilization, including pore formation and ion channel induction.
- Morphological analysis revealed substantial cell damage upon DH-L treatment.
- Dry-heating increased lysozyme's hydrophobicity, surface activity, and positive charge.
Conclusions:
- Dry-heated lysozyme (DH-L) exhibits potent antimicrobial activity against E. coli.
- DH-L's enhanced efficacy is attributed to increased membrane disruption.
- The modified biophysical properties of DH-L are key to its improved antibacterial action.
- DH-L represents a promising natural antimicrobial agent for various applications.
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