Expansion microscopy reveals unique ultrastructural features of pathogenic budding yeast species

Abstract

AbstractCandida albicansis the most prevalent fungal pathogen isolated from patients with candidemia. As is the case for many other fungi, the complex life cycle ofC. albicanshas been challenging to study with high-resolution microscopy techniques due to its small size. We employed ultrastructure expansion microscopy (U-ExM) to directly visualise sub-cellular structures at high resolution in theC. albicansyeast and during its transition to hyphal growth. NHS-ester pan-labelling in combination with immunofluorescence (IF) provided the first comprehensive map of nucleolar and mitochondrial dynamics through theC. albicanscell cycle. Analysis of microtubules (MTs) and spindle pole bodies (SPBs) stained with marker proteins suggests that contrary to the pole-to-pole arrangement observed inSaccharomyces cerevisiae, C. albicansyeast cells display a unique side-by-side arrangement of SPBs with a short mitotic spindle and longer astral MTs (aMTs) at the pre-anaphase stage. Modifications to the established U-ExM protocol enabled the expansion of several medically relevant human fungal pathogens, revealing that the side-by-side SPB configuration is a plausible conserved feature shared by many fungal species. We highlight the power of U-ExM to investigate sub-cellular organisation and organellar dynamics at high resolution and low cost in poorly studied, medically relevant microbial pathogens.