FIG 1.
MAMHS mediates adhesion of nonadherent E. coli cells to host cells and is nontoxic. (A and B) Attachment of E. coli BL21 cells expressing mCherry (red) and transformed with pBAD (A) or pBAD containing MAM from E. coli HS (BL21+MAMHS) (B) to HeLa cells. Cells were fixed and stained for actin (green) and DNA (blue) following a 1-h infection. The arrow indicates attached bacteria. Bar, 20 μm. (C) The numbers of attached bacteria were quantified by image analysis, and the data represent the means ± SEMs based on analysis of at least 300 HeLa cells over three independent experiments. Significance was determined using Student's t test. *, P ≤ 0.05. (D) The attachment of BL21 cells to HeLa cells was also quantified by dilution plating, and the results are expressed in relation to the CFU counts from the input controls (100%). (E) The cytotoxicity of BL21 toward HeLa cells was determined using LDH release assays and is normalized to that toward untreated (0%) and Triton X-100-treated (100%) controls. The results in panels D and E are means ± SEMs (n = 3), and significance was determined using Student's two-tailed t test. *, P ≤ 0.05.