Figure 2
From: How type 1 fimbriae help Escherichia coli to evade extracellular antibiotics
Fimbriae overexpression yielded higher adhesion efficiency, bacterial burden and intracellular survival of E.coli in macrophages.
(a) Timeline of the flow cytometric determination of the bacterial adhesion efficiency to macrophages. (b) Expression of type 1 fimbriae changed the adhesion efficiency of E.coli to macrophages. Macrophages were incubated with E.coli fim↑, wt fim and ∆fim, respectively, at bacteria-to-macrophage ratios from 0.5 to 32. Error bars are S.D. from n = 8 independent experiments. (c) Higher adhesion efficiency depended on functional type 1 fimbriae, as the mannose analogue αMM decreased adhesion of fim↑ but not ∆fim. (d) Treatment of macrophages with LatB yielded less GFP-positive macrophages. (e) The bacterial burden on macrophages was higher for fim↑ compared to ∆fim. Images of 25 randomly chosen macrophages were analyzed for total counts of adherent bacteria. (f) Macrophages 0.5 hours post infection with fim↑ and (g) ∆fim at a ratio of 10:1 bacteria per macrophage, respectively. GFP-expressing bacteria are colored in green, actin-binding phalloidin is colored in grey. One adherent ∆fim bacterium is indicated by the yellow arrow. Scale bar is 5 μm. (h) αMM decreased survivors of fim↑ inside macrophages. Variance of population means was analyzed using a one way ANOVA. Upper-case letters mark significant differences based on a post hoc Tukey and Bonferroni test. Pairs of samples that have no letter in common have significantly different means at p < 0.05; i.e., samples with the label A are significantly different from samples with the label B/C, but not from samples with the label A/B. cfu, colony forming units; fim↑, fimbriae overexpression strain; wt, fimbriae wild type strain; ∆fim, fimbriae knockout strain; GFP, green fluorescent protein; αMM, alpha-methyl mannosepyrannoside; LatB, LatrunculinB; h, hours.
