The Effects of Milk Fat Globule Membrane Proteins on the Immune Response of Drosophila melanogaster

This project presents the effect of milk fat globule membrane (MFGM) proteins, specifically lactoferrin, on the immune response of Drosophila melanogaster when exposed to Serratia marcescens, an entomopathogenic bacterium known to infect the flies. Lactoferrin is thought to have antibacterial properties by binding iron and diminishing the supply required by bacteria. However, despite this suspected link, there is a lack of literature regarding the direct effect of these proteins on the immunology and gastrointestinal flora of organisms. In this experiment, lactoferrin protein was obtained through RNA extraction, Polymerase Chain Reaction (PCR), and bacterial transformation. The plasmid was subject to a double digest using restriction enzymes EcoRV and NotI, then ligated. While successful bacterial transformation was achieved and verified through PCR on transformed colonies, pre-transformed Escherichia coli were ordered for Dharmacon GE Life Sciences. The lactoferrin produced by these cells was used because the cells arrived before bacterial transformation was successful. After protein purification, lactoferrin was fed to D. melanogaster, which were transferred to tubes containing MacConkey agar or agar inoculated with S. marcescens. The survival rate was recorded, and dead flies were crushed and plated to determine the magnitude of infection. When plates of the experimental groups (bred on milk) and control groups (never exposed to milk) were compared, the experimental groups had significantly less bacterial growth, establishing the MFGM proteins’ antibacterial properties. The death rates also suggested that MFGM proteins did have a positive effect on the immune response of D. melanogaster. All the collected data was shown to be statistically significant by conducting a Chi-square test and a two sample T-test. Thus, it can be concluded that lactoferrin increases the immunity of Drosophila to S. marcescens, and this data correlates to the benefits of drinking whole milk and breast milk. This correlation will be useful in creating anti-bacterial pharmaceutics or alternative milk products.