Fig 3. Reduced binding of A. phagocytophilum to ISE6 cells caused by omt mutation or inhibition with AdOx.

A) Mutation of omt (ΔOMT; green bar) in A. phagocytophilum HZ caused a reduction in the number of bacteria adhering to tick cells when compared to the number of wild-type bacteria per tick cell (purple bar). Bacteria purified from HL-60 cells were incubated with ISE6 cells for 30 min at room temperature. Unbound bacteria were removed using vigorous washes and the remaining attached bacteria were counted using immunofluorescence microscopy. The difference in binding was statistically significant (t-value = -4.1011; P = 0.0001). Bars represent the average number of adherent bacteria per cell, and vertical lines indicate the standard error of the mean. B) Effect of AdOx (Adenosine dialdehyde; an inhibitor of SAM-depended methyltransferases) on adherence of A. phagocytophilum HZ wild-type to ISE6 cells in comparison to the effect of mutation of the omt gene in ΔOMT bacteria. Wild-type A. phagocytophilum were incubated with different concentrations of AdOx for 1 hr while ΔOMT was held in medium alone, and then mixed with ISE6 cells. Bars represent the average number of bacteria bound to ISE6 cells in each treatment, and bars with the same letter are not significantly different, whereas different letters indicate a significant difference (P<0.001). The standard error of the mean from four replicates is shown as vertical lines.