Localization of antimicrobial responses in the house fly alimentary canal

House flies breed in septic environments and as a result are exposed to numerous species of microorganisms. While many of these microbes are pathogens to other animals, including insects, house flies remain remarkably unharmed even when they ingest and harbor these microorganisms. One protective mechanism in the house fly may be the secretion of antimicrobial effector molecules in the alimentary canal. This research focuses on determining the temporal and spatial expression of four antimicrobial molecules in the entire alimentary canal of flies fed two species of pathogenic bacteria (Bacillus cereus and E. coli O157:H7). The expression of lysozyme, a broad-spectrum digestive and antimicrobial enzyme, and three antimicrobial peptides (AMPs), diptericin, cecropin, and defensin was determined via immunoflourescence microscopy of whole alimentary canals, including the crop, proventriculus, midgut, hindgut and rectum. The location of antimicrobial gene expression in relation to the proximity of ingested bacteria will be discussed. Assessing the role of the house fly humoral immune response in fly-microbe interactions may lead to potential avenues of vector control or even novel antibacterial compounds for human medical use.