Surface Rigidity Change of Escherichia coli after Filamentous Bacteriophage Infection

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.

Antibiotic-induced modifications of the stiffness of bacterial membranes

“…This allowed discriminating two well-defined stiffness peaks, one centered at 3 MPa that can be attributed to the typical stiffness of the substrate and the second at 300 ± 70 kPa, associated with the stiffness of the E. coli membrane. Indeed, such values are in good agreement with those obtained by similar studies on the same kind of bacteria, confirming the attribution (Chen et al, 2009). To better compare these results with the ones collected in different environmental conditions we have highlighted these two peaks in red (bacteria) and in black (substrate).…”

Characterization of Curli A Production on Living Bacterial Surfaces by Scanning Probe Microscopy

“…3 a shows the approach curves measured on the cell surfaces that correspond to different stiffness values for each strain. As the initial nonlinear part of the forceindentation curve is dependent on the cellular elasticity during indentation (15,17), it was used to calculate Young's modulus, which relates to cell wall stiffness. Young's modulus was calculated using Sneddon's variation of the Hertz model for a conical tip, as described previously (15)(16)(17)(18),…”

Effect of colistin exposure and growth phase on the surface properties of live Acinetobacter baumannii cells examined by atomic force microscopy

“…Interestingly, a reduction in k b has been documented following exposure of Gram-negative bacterial strains to antimicrobial agents [43–45]. Similarly, colistin-induced destabilisation of the LPS monolayer of colistin-susceptible A. baumannii upon treatment with MIC concentrations (1 mg/L) may account for the decreased k b observed (Fig.…”