A Re-Evaluation of the Relationship between Morphology and Pathogenicity in Species.

Many pathogenic species possess the ability to undergo a reversible morphological transition from yeast to filamentous cells. In , the most frequently isolated human fungal pathogen, multiple lines of evidence strongly suggest that this transition is associated with virulence and pathogenicity. While it has generally been assumed that non- species (NACS) are less pathogenic than , in part, because they do not filament as well, definitive evidence is lacking. Interestingly, however, a recent study suggests that filamentation of NACS is associated with reduced, rather than increased, pathogenicity. These findings, in turn, challenge conventional views and suggest that there are fundamental evolutionary differences in the morphology-pathogenicity relationship in vs. NACS. The findings also raise many new and intriguing questions and open new avenues for future research, which are discussed.