The affect of Pseudomonas aeruginosa ingestion on antimicrobial peptide (AMP) and lysozyme expression in the common housefly (Musca domestica L.)

The common house fly (Musca domestica L.) lives and thrives in one of the most septic niches on Earth, making bacterial exposure imminent. House flies often ingest bacteria and have both physical and chemical defenses utilized to protect themselves from harmful microbes. For example, defense molecules such as antimicrobial peptides (AMPs) and lysozyme are manufactured by tissues both locally (gut epithelium) and systemically (fat body). These molecules serve to neutralize or lyse bacteria, yet some species are still able to persist through the digestive tract, making the fly a potential biological vector. We found that Pseudomonas aeruginosa was able to survive passage through the fly alimentary canal and exit the digestive tract by 10 h post-ingestion. This study aimed to elucidate the systemic and local AMP and lysozyme responses in house flies after P. aeruginosa ingestion. We analyzed the temporal expression of three AMPs (cecropin, defensin and diptericin) and lysozyme 1, 2, 6, 8, and 10 h after ingesting a known amount of P. aeruginosa. Tissue-specific expression was measured on both the mRNA and protein level using qRT-PCR and Western analysis. It is suspected that P. aeruginosa is able to pass through the fly alimentary canal either due to AMP and lysozyme resistance, or by bacteria altering the expression of AMPs and/or lysozyme in order to enhance their survival. By understanding the spatial and temporal molecular interactions between house fly defenses and P. aeruginosa, we can better understand the potential flies have for vectoring these bacteria.