Quantitative Changes in the Elasticity and Adhesive Properties of Escherichia coli ZK1056 Prey Cells During Predation by Bdellovibrio bacteriovorus 109J

Abstract

Atomic force microscopy (AFM) was used to explore the changes that occur in Escherichia coli ZK1056 prey cells while they are being consumed by the bacterial predator Bdellovibrio bacteriovorus 109J. Invaded prey cells, called bdelloplasts, undergo substantial chemical and physical changes that can be directly probed by AFM. In this work, we probe the elasticity and adhesive properties of uninvaded prey cells and bdelloplasts in a completely native state in dilute aqueous buffer without chemical fixation. Under these conditions, the rounded bdelloplasts were shown to be shorter than uninvaded prey cells. More interestingly, the extension portions of force curves taken on both kinds of cells clearly demonstrate that bdelloplasts are softer than uninvaded prey cells, reflecting a decrease in bdelloplast elasticity after invasion by Bdellovibrio predators. On average, the spring constant of uninvaded E. coli cells (0.23 +/- 0.02 N/m) was 3 times stiffer than that of the bdelloplast (0.064 +/- 0.001 N/m) when measured in a HEPES-metals buffer. The retraction portions of the force curves indicate that compared to uninvaded E. coli cells bdelloplasts adhere to the AFM tip with much larger pull-off forces but over comparable retraction distances. The strength of these adhesion forces decreases with increasing ionic strength, indicating that there is an electrostatic component to the adhesion events.

Predation Efficacy of <i>Bdellovibrio bacteriovorus</i> on Multidrug-Resistant Clinical Pathogens and Their Corresponding Biofilms

“…With the increased occurrence of MDR and XDR clinical pathogens, many of which have brought about therapeutic challenges, the concept of utilizing predatory bacteria as live antimicrobials is gaining momentum. However, the majority of previous research has failed to investigate whether predation of B. bacteriovorus against bacteria is affected by antibiotic susceptibility (10,20). Hence, further research on the predation efficacy of B. bacteriovorus against MDR or XDR clinical pathogens and their biofilms is encouraged.…”

Impacts of Hematite Nanoparticle Exposure on Biomechanical, Adhesive, and Surface Electrical Properties of Escherichia coli Cells

“…The spring constants (k b ) were determined from the slope of the linear portion of the constant compliance region, which is due to elastic deformation of the bacterium, as mentioned above (52). When the tip interacts with a cell, two springs are present in series (the cell and the cantilever).…”

“…For example, hardness or elasticity changes likely influence the surface structural flexibility, the production of mechanical energy for cell division, and cell motility. As for adhesiveness, the cell microenvironment is normally composed of an extracellular matrix (ECM) with specific molecules that allow the cell to adhere to its surroundings (52). Sorption of NPs on cells may alter the adhesion characteristics and affect a variety of microbial processes (e.g., bacterial colonization) (20).…”

Atomic Force Microscopy of Biofilms—Imaging, Interactions, and Mechanics

“…Bdellovibrio bacteriovorus was shown to prevent biofilm formation and destroy established biofilms. This work was extended by Volle et al [64] who used force spectroscopy to observe that the spring constant of predated E. coli cells was three times softer than that of normal cells and that there was change in cell wall morphology on predation, as there was much larger adhesion forces between an AFM tip and predated cells. This important work demonstrates that dynamic events in living unfixed cells can be characterized and investigated using AFM.…”