Fig. 4: T4SS promotes biofilm formation by AIEC on epithelial cells. | Nature Communications

Fig. 4: T4SS promotes biofilm formation by AIEC on epithelial cells.

From: High-throughput fitness screening and transcriptomics identify a role for a type IV secretion system in the pathogenesis of Crohn’s disease-associated Escherichia coli

Fig. 4

a Biofilm formation by different AIEC strains on abiotic surfaces. Data are mean change ± SEM in the percentage of biofilm formation relative to wild type; n = 10 biologically independent replicates examined over three independent experiments. Groups were compared using two-tailed Mann–Whitney U test, ****P < 0.0001 b Cellulose secretion by AIEC microcolonies. Immunofluorescence staining of Caco-2 cells infected with wild-type or ∆bcsA AIEC strains. Right panel, cellulose (red); middle panel, bacteria (green); left panel, merge of both panels showing Caco-2 cells (gray). White arrows indicate individual bacteria. Scale bar is 20 µm. Panels are representative of 15 images per group obtained from three biologically independent replicates. c traA is not required by AIEC to adhere to epithelial cells. Data are mean change ± SEM in adhesion relative to wild-type strain; n = 5 biologically independent replicates obtained from two independent experiments. Groups were compared using unpaired two-tailed t-test. d traA does not affect cell invasion by AIEC. Cell adhesion and invasion were quantified for the different AIEC strains indicated. Data are the mean fold change ± SEM in invasion relative to wild-type strain; n = 5 biologically independent replicates obtained from two independent experiments. Groups were compared using unpaired two-tailed t-test. e Immunofluorescence staining of different AIEC strains (green) showing microcolonies on epithelial cells (gray). White arrows indicate individual bacteria. Panels are representative of 20 images per group; n = 3 biologically independent replicates. Scale bar is 20 µm. f Microcolony formation was quantified using 20 fields of view per all groups except bcsA (23 fields of view); n = 3 biologically independent replicates. Data are the mean ± SEM microcolony formation relative to wild-type strain. Groups were compared using two-tailed Mann–Whitney U test, ****P < 0.0001. g Fold change in gene expression of different tra genes in AIEC wild-type strain upon infecting Caco-2 cells; n = 5 biologically independent replicates (n = 3 for traM) obtained from two independent experiments. Groups were compared using Holm–Sidak method for multiple t-tests (two-tailed). Adjusted P values are 0.016645 for traG, 0.03507 for traD, 0.033591 for traK, 0.027143 for traBH, and 0.010832 for traM.

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