Genomic Landscape Underlying Biofilm Formation Diversity in Nakaseomyces glabratus Clinical Isolates.

Biofilm formation is a key determinant of persistence and pathogenicity in fungal infections, yet the genetic basis underlying its variability among clinical isolates remains poorly understood. In this study, a collection of 95 N. glabratus clinical isolates was analyzed in terms of biofilm formation capacity, revealing large phenotypic diversity. Interestingly, urinary tract associated isolates were found to produce, on average, twice as much biofilm as the remaining isolates. A more in-depth analysis was carried out focusing on a selection of three of the lowest biofilm producing and four of the highest biofilm producing isolates. Higher total biofilm mass was found to consistently correlate with higher metabolic activity and carbohydrate extracellular matrix content, while no correlation with virulence against the Galleria mellonella infection model could be detected. Whole-genome sequencing of these high and low biofilm producing strains led to a list of 184 genes whose mutation may underlie biofilm formation variability. Deletion of 24 of these genes, identified BST1, EST3, LSM7, AMS1 and ZCF21 as previously uncharacterized contributors to biofilm formation, whose disruption results in a measurable reduction in biofilm biomass. Altogether, the obtained knowledge suggests within-host positive selection in the urinary tract, for N. glabratus specialization towards biofilm growth. The identification of new effectors of biofilm formation is consistent with the existence of a multi-layered network that connects transcriptional regulation and cell surface architecture in biofilm development.