To investigate if it is possible to robustly distinguish the Raman signal from C. parvum with E. coli, V. cholerae, B. cereus, C. difficile we also performed single cell Raman measurements on these pathogens. Representative SEM images of each pathogen are shown in Figures and -S6. Since it is known that the cell wall composition, as well as the inner cell of these pathogens are different, we anticipated that the Raman signals should reflect these differences at the single-cell level. For example, as mentioned above, the biochemical composition of the oocyst cell wall structure consists of carbohydrate components, medium and long fatty acids, proteins, and aliphatic hydrocarbons . In comparison, the cell wall of E. coli cells are mainly lipid-rich, and contain a peptidoglycan layer further into the cell . For B. cereus and C. difficile we measured the spectra of spores, the state they are often found in the environment. In spores, the outer layers are protein and peptidoglycan rich, whereas the inner layers consist of up to 25 % CaDPA, a common spore biomarker .