Chitin and chitosan quantification in fungal cell wall via Raman spectroscopy

Investigation of cell wall composition is necessary to understand the interactions between fungi and the environment as it is the external layer exposed to stimuli and detected by other organisms. Pochonia chlamydosporia and Akanthomyces lecanii, two fungal species living in the soil and infecting nematodes and insects, exhibit endophytic interactions with various plant species. Determination of cell wall composition is essential to understand the mechanisms underlying these interactions. Therefore, in this study, for the first time, we assessed the relative amounts of chitin and chitosan in the cell walls of P. chlamydosporia (PC123) and A. lecanii (69NZ, 85SCT, 126KNY, and 447SAF) via Raman spectroscopy. The isolate with the highest chitosan percentage was 69NZ, followed by 85SCT, PC123, 447SAF, and 126KNY. Moreover, combination with conventional approaches for chitin and chitosan quantification yielded quantitative results for all cell wall components. Overall, these results highlight the mechanisms by which fungi exhibit chitosan resistance and avoid detection by the host plant during root colonization.