Table 1.

Summary of spring constants for the cantilever tip and untreated and hematite-treated E. coli cells^a

Tip or group of cells	Slope (nm/nm)b	Spring constant (nN/nm)
Cantilever		0.03 ± 0.01
Untreated E. coli cells	0.31 ± 0.02	0.01 ± 0.01
Hematite-treated E. coli cells	0.90 ± 0.02	0.28 ± 0.11

^aThe average data and standard deviations are presented. The standard deviations of k_b (the spring constants of the cells) were computed by the method of propagation of uncertainty.

^bThe slope in the table (nm/nm) was converted from the slope in the force-distance curve (nN/nm) by dividing by the spring constant of the cantilever (k_c). A total of 250 force-distance curves on 3 untreated and 5 hematite-treated cells were selected to determine the slopes in the corresponding linear constant compliance region.