<i>Y</i>. <i>pestis</i> causes complete proventricular blockage in <i>O</i>. <i>montana</i> fleas.

<p>The left panels show the typical blockage phenotype in <i>O</i>. <i>montana</i> fleas immediately after a feeding attempt. Fresh red blood (arrows) that was unable to enter the midgut (MG) is seen in the esophagus (E). The fleas were infected with GFP-expressing <i>Y</i>. <i>pestis</i>. The middle and right panels are images of the dissected digestive tracts from the same fleas visualized by DIC and a combination of DIC + fluorescence microscopy, respectively, and confirm the presence of a dense <i>Y</i>. <i>pestis</i> biofilm that completely fills and blocks the proventriculus (PV). Scale bars = 100 μm.