Table 1.

Experimental occurrences of MscS-like and MscL-like channels in patches of WT E. coli and V. cholerae

Species 
 No. MscS per patch No. MscL per patch p0.5MscS/p0.5MscL MscS/µm2 (r = 1.5 µm) MscL/µm2 (r = 1.5 µm) Patch r*, µm (γ0.5 = 12 mN/m) Patch area*, µm2 MscS/µm2MscL/µm2
E coli 46 ± 14 61 ± 40 0.60 ± 0.05 3.6 ± 1.8 4.3 ± 2.2 1.5 ± 0.3 14.7 ± 5 3.6 ± 1.8 4.3 ± 2.2 
V cholerae 17 ± 9 164 ± 100 0.48 ± 0.04 1.2 ± 0.7 11 ± 4 1.37 ± 0.3 12.4 ± 6.3 1.5 ± 0.8 14 ± 5 
Species 
 No. MscS per patch No. MscL per patch p0.5MscS/p0.5MscL MscS/µm2 (r = 1.5 µm) MscL/µm2 (r = 1.5 µm) Patch r*, µm (γ0.5 = 12 mN/m) Patch area*, µm2 MscS/µm2MscL/µm2
E coli 46 ± 14 61 ± 40 0.60 ± 0.05 3.6 ± 1.8 4.3 ± 2.2 1.5 ± 0.3 14.7 ± 5 3.6 ± 1.8 4.3 ± 2.2 
V cholerae 17 ± 9 164 ± 100 0.48 ± 0.04 1.2 ± 0.7 11 ± 4 1.37 ± 0.3 12.4 ± 6.3 1.5 ± 0.8 14 ± 5 

Multiple traces, as shown in Fig. 2, were Rs corrected, and numbers of MscS-like and MscL-like channels as well as midpoint pressures for each population were determined. The pressure midpoint (p0.5) for Eco MscL was equated to membrane tension γ0.5 = 12 mN/m acting on channels, from where the radii of patch curvature and areas were calculated according to the law of Laplace (γ = Δpr/2). The densities (channels/µm2) were then deduced for MscS-like and MscL-like channels individually, first on the assumption that the average patch radius for V. cholerae preparations is the same as for E. coli (columns 4 and 5) and independently with the assumption that MscLs in both preparations gate with the same midpoint γ0.5 = 12 mN/m (columns 6 through 9). Data are presented as mean ± SD (n = 12 for E. coli and n = 19 for V. cholerae). The midpoint ratios p0.5MscS/p0.5MscL for the two species (column 3) are significantly different at a 0.006 level according to two-tailed unequal variance t test.

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