Fig 5.

OmpA modulates Sodalis biofilm formation in the tsetse gut. (A) A newly developed per os colonization assay was used to determine if Sodalis PT cells could establish an infection in Gmm^WT and Gmm^Apo fly guts. Five days postinoculation, Sodalis PT was found at a density of ∼10⁶ cells in both host backgrounds. (B) Biofilm formation in the tsetse gut was visualized by orally inoculating Gmm^WT and Gmm^Apo flies with a strain of Sodalis (Sodalis pGFP) that expresses green fluorescent protein. Fluorescing microcolonies, indicated by a white arrow, were present in Gmm^WT flies 1 day postinoculation with Sodalis pGFP. Three days postinoculation, these microcolonies are more pronounced in Gmm^WT flies. Additionally, Sodalis pGFP colonies are also beginning to form at this time in Gmm^Apo flies. Bars, 50 μm. (C) Colonization of Gmm^WT fly guts by Sodalis PT and Sodalis ΔOmpA strains. Sodalis ΔOmpA cells exhibit an initial colonization defect but, by 5 days postinoculation, reach a density similar to that of Sodalis PT cells. (D) Colonization of Gmm^Sgm− fly guts by Sodalis PT and Sodalis ΔOmpA strains. Sodalis ΔOmpA cells cannot colonize tsetse when their native counterparts are absent. In panel A, colonization assays were performed in duplicate and data are presented as the means ± standard deviations. In panels C and D, each symbol represents one fly gut, and the dotted line indicates the assay's limit of detection. Statistical significance in C and D was determined by the Mann-Whitney test.