Figure 1: Physical barriers-mediated compartmentalization of insect midgutduring blood digestion.This figure represents the compartmentalization of mosquito gut by two differentbarriers during blood digestion. The purpose of this compartmentalization is toinhibit the direct contact of food (shown in red color) and endogenous microbes(M) with the midgut epithelium (E). The blood bolos remains restricted to theendoperitrophic space of the midgut, which is surrounded by an accelularlayer called the peritrophic matrics (PM). This layer also defines boundariesof the microbial community within the bolus area. As shown here the microbesregulate several processes that are beneficial to the insect host. PM allows thesmaller-sized digestive enzymes (blue arrowheads) and digestive products ofthe food (purple arrowheads) to transverse in opposite directions. The solubleimmune elicitors (sImE, the dark green circles) released by the microbes caneasily cross through the PM but not the peroxidases-mediated crosslinkedmucin barrier (ML). Please see the main text for other details.