Distinct properties of human pathogenic Candida species revealed by systematic comparative phenotypic screening of clinical isolates

ABSTRACT Fungi associated with humans include several Candida species that rely on phenotypic plasticity for persistence and pathogenicity. Key adaptive traits, such as adherence, stress resistance, and biofilm formation, enable survival in diverse host niches. However, the degree of intra- and interspecific phenotypic variation across human-associated Candida species has not been systematically characterized. We analyzed 1,366 clinical isolates representing 13 Candida species using high-throughput quantitative fitness profiling under controlled environmental stressors, antifungal exposure, and biofilm-inducing conditions. The resulting data set revealed both conserved and species-specific adaptive signatures. Isolates consistently segregated into three phenotypic archetypes: heat-resistant fast growers, osmo-sensitive strains, and slow growers. A robust inverse correlation was detected between basal growth rate and stress resistance, reflecting a fundamental physiological trade-off. In addition, distinct resistance profiles against antifungal agents and environmental stressors highlighted species-specific adaptive trajectories and ecological specialization. Despite genetic homogeneity, C. parapsilosis isolates displayed striking phenotypic heterogeneity. By contrast, the closely related C. albicans and C. dubliniensis exhibited divergent stress-response profiles. High-resolution fitness mapping of C. glabrata isolates revealed that temperature stress progressively disrupts multiple cellular functions, whereas osmotic stress exerts more discrete, pathway-specific effects. Our systematic phenotypic landscape analysis delineates conserved versus species-specific adaptive properties among human-associated Candida species, providing a comparative framework to interrogate evolutionary trends, ecological specialization, and pathogenic potential. IMPORTANCE Human-associated fungi include multiple Candida species whose persistence relies on phenotypic plasticity enabling adherence, stress resistance, and biofilm formation. Yet, the extent of phenotypic variation within and across species remains poorly defined. We profiled 1,366 clinical isolates from 13 Candida species using high-throughput quantitative fitness assays under environmental stress, antifungal exposure, and biofilm-inducing conditions. The analysis uncovered both conserved and species-specific adaptive traits. Isolates segregated into three major phenotypic archetypes: heat-resistant fast growers, osmo-sensitive strains, and slow growers. A consistent inverse correlation emerged between basal growth rate and stress resistance, revealing a fundamental physiological trade-off. Species-specific resistance signatures further reflected ecological specialization and divergent adaptive trajectories. Our quantitative framework establishes, for the first time, a comparative phenotypic landscape across a multispecies collection of human-associated Candida , providing new insights into their ecological specialization and adaptive strategies.