Identifying Giardia lamblia’s stages using Raman microscopy*

Giardiasis is a global parasitic infection caused by the protozoan Giardia. This parasite has two extreme life stages, trophozoites and cysts. Current detection methods primarily rely on morphological and confocal fluorescence techniques, which lack molecular specificity. In this study, we use label-free Raman microscopy to identify stage-specific molecular signatures in Giardia trophozoites and cysts. Our results reveal notable spectroscopic differences, including important components of the cyst wall such as N-acetylgalactosamine (GalNAc) and N-acetylglucosamine (GlcNAc). Other observed changes are in heme-protein oxidation states and lipid-protein metabolism during encystation. Complementary confocal fluorescence microscopy results corroborate the Raman outcomes. These findings show that Raman microscopy can effectively distinguish between different life cycle stages of Giardia based on their molecular makeup, providing a strong complement to traditional methods used in biological investigations.