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Surface rigidity change of Escherichia coli after filamentous bacteriophage infection
Yi-Yang Chen1, Chien-Chen Wu, Jye-Lin Hsu
1Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu, Taiwan.
Abstract:
In this study, the feasibility using atomic force microscopy (AFM) to study the interaction between bacteriophages (phages) and bacteria in situ was demonstrated here. Filamentous phage M13 specifically infects the male Escherichia coli, which expresses F-pili. After infection, E. coli become fragile and grows at a slower rate. AFM provides a powerful tool for investigating these changes in a near-physiological environment. Using high-resolution AFM in phosphate-buffered saline, the damage to the lipopolysaccharide (LPS) layer on the outer membrane of the M13 phage-infected E. coli was observed. The membrane became smoother and more featureless compared to those that were not infected. Besides, the force-distance (f-d) curves were measured to reveal the surface rigidity change in E. coli after M13 phage infection. The effective spring constant and Young's modulus of E. coli decreased after M13 phage infection. Furthermore, the AFM tip was pressed against E. coli to study the response of E. coli under load before and after M13 phage infection. The results showed that after infection E. coli became less rigid and the membrane was also damaged. However, the stiffness changes, including the spring constant and Young's modulus of E. coli, are negligible after M13 phage infection compared with those in previous reports, which may be one of the reasons that E. coli still can maintain its viability after filamentous phage infection.
Insights
Atomic force microscopy (AFM) reveals how M13 bacteriophages damage Escherichia coli membranes. Infected E. coli show reduced surface rigidity and LPS layer damage, impacting bacterial fragility.
Area of Science:
- Microbiology
- Biophysics
- Materials Science
Background:
- Bacteriophages (phages) are viruses that infect bacteria.
- Filamentous phage M13 specifically infects male Escherichia coli (E. coli) expressing F-pili.
- Phage infection alters bacterial physiology, making E. coli fragile and slowing growth.
Purpose of the Study:
- To demonstrate the feasibility of using atomic force microscopy (AFM) to study phage-bacteria interactions in situ.
- To investigate the physical and morphological changes in E. coli after M13 phage infection.
Main Methods:
- High-resolution AFM was used to image M13 phage-infected E. coli in phosphate-buffered saline.
- Force-distance (f-d) curves were measured to assess surface rigidity.
- AFM tip indentation was performed to study E. coli response under load.
Main Results:
- M13 phage infection damaged the lipopolysaccharide (LPS) layer on the E. coli outer membrane, resulting in a smoother surface.
- Infected E. coli exhibited decreased surface rigidity, indicated by reduced effective spring constant and Young's modulus.
- AFM analysis showed E. coli became less rigid and the membrane was damaged upon M13 phage infection.
Conclusions:
- AFM is a viable tool for in situ analysis of phage-bacteria interactions and their effects on bacterial cell properties.
- M13 phage infection induces significant changes in E. coli membrane structure and surface mechanics.
- Observed stiffness changes were less pronounced than in previous reports, potentially explaining E. coli's retained viability post-infection.
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