Fig. 6

ESX?1 secretion is required for macrophage independent BBB crossing in vivo. Infected blood vessel (depicted in red to facilitate comparison with Figures 3 and 4) found in brain tissue of 9 dpf phagocyte?depleted Tg(Fli1:GFP)^y1 larva, systemically infected with M. marinum eccCb1::tn (green), nuclei are stained with DAPI (cyan). (a) Electron microscopy, (b) confocal microscopy, and (c) correlative light and electron microscopy, showing an abundant amount of extracellular ESX?1?deficient M. marinum restricted to a blood vessel. Scale bar = 5 ?m. Also notice the regular shape of the blood vessel. (d) Higher magnification of the highly infected blood vessel depicted in (c), showing that bacteria did not cross or disrupt the basal lamina (red dotted line). (e) Although esx?1 mutant bacteria were mainly found in the lumen of the vessel, sporadically one was found to invade endothelial cell (*). (f) Cross section of infected (red fluorescent esx?1 mutant) and non?infected blood vessels (green) of Tg(Fli1:GFP)^y1 larva, showing high bacterial load in a single blood vessel with subsequent enlargement of the vessel lumen. En = Endothelial cell (nucleus), Er = Erythrocyte, M = M. marinum, N = nucleus, Scale bar e and f = 1 ?m