Fig. 6.

TEM analysis. Strep. mutans wild-type, UA159, BrpB-deficient mutant, JB409, BrpB-complemented strain, JB409C, BrpB- and BrpA-deficient double mutant, JB819, and BrpB- and BrpA-complemented strain, JB819C, were grown in BHI, pH 7.4, until mid-exponential phase. When compared to the parent strain, UA159, both JB409 and JB819 displayed patches of low-density areas (shown by arrows in the middle and bottom panels), as a result of BrpB deficiency. In addition, the nucleoid of JB409 and JB819 also appeared rougher when compared to UA159. Complementation with a copy of the respective wild-type gene plus its cognate promoter(s) in JB409C and JB819C was able to restore the wild-type phenotype. Images in the top panel were taken at a magnification of ×10 000 and those in the middle and bottom panels were taken at ×50 000. Numbers under the image panels are surface areas as means (±sd) of the cell sections.