Bdellovibrio bacteriovorus , a gram-negative bacterium, preys on other gram-negative bacteria including Escherichia coli by burrowing into and occupying the periplasmic space between the inner and outer membranes of the prey bacteria. From our previous research, this predator-prey unit called a bdelloplast, exhibits changes in the texture of the cell surface membrane that differs from healthy, un-invaded prey cell membranes. In addition, many prey cells also displayed morphological changes during and after a B. Bacteriovorus attack. Also, we have shown that B. bacteriovorus successfully perturbs and/or destroys biofilm grown at an air-liquid interface. We investigate the changes in surface properties such as elasticity and rigidity of E. coli in biofilms before, during, and after B. bacteriovorus attacks using atomic force microscopy and quantitative force measurements. The biofilms are imaged in liquid to stimulate the E. coli ?s growing environment as closely as possible, providing more accurate measurements of the bacteria?s surface properties in situ .