TABLE 2.

Summary of advantages and disadvantages associated with the bacterial immobilization methods employed in this study

Immobilization method	Advantages	Disadvantages
Mechanical trapping	Simple preparation	Rod-shaped bacteria are difficult to trap
	No chemical pretreatment of either the tip or bacteria	Cells may be compressed as a result of applied vacuum
	Physicochemical properties of bacterial cell remain unchanged	EPS may accumulate on the top of a trapped bacterium
	Exact positioning of the tip on the bacterial cell surface
	Contact area can be estimated based on the dimensions of the tip
Physical adsorption	Simple preparation	Chemical treatment of the substratum is required
	Bacteria with different shapes and dimensions can be studied	Physicochemical properties of bacterial cell surface are possibly affected by the surface modification
	Exact positioning of the tip on the bacterial cell surface	Immobilization not always adequate for different strains (11)
	Contact area can be estimated based on the dimensions of the tip
Bacterium-coated tip	Versatile choice of substratum	Long and difficult preparation procedure
		Requires chemical treatment of both bacterial cell and substratum surface
		Physicochemical and mechanical properties of the bacterial cell surface change
		The number of interacting cells is unknown, as is their spatial orientation when interacting with the substratum
		Bacterium-coated tips need to be checked regularly for full coverage by electron microscopy