Morphological and genetic characterization of novel Sarocladium spinificis strains in association with Coccidioides posadasii.

UNLABELLED: Sarocladium is a fungal genus containing diverse members with roles as pathogens of plants and animals, endophytes, and biocontrol agents. This study characterizes two Sarocladium spinificis strains isolated from patients diagnosed with coccidioidomycosis. Morphological, phylogenetic, and genomic analyses confirmed their classification within the Sarocladium genus, closely related to S. spinificis. Both strains exhibited mycelial growth at 24°C and 37°C, with distinct morphological features. Comparative genomic analysis identified unique orthologous clusters and functional gene families associated with diverse carbon utilization and potential pathogenicity. Notably, these strains' genomes contain many secreted proteins, carbohydrate-activated enzymes, and peptidases, highlighting their metabolic versatility. Co-cultivation experiments revealed that S. spinificis strains CA16 and CA18 both inhibited the growth of Coccidioides posadasii, suggesting antagonistic interactions and potential antifungal properties. These findings underscore the ecological and clinical significance of S. spinificis and its impact on microbial communities, advancing our understanding of its diversity, pathogenic potential, and antifungal capabilities.

IMPORTANCE: Accurate identification and characterization of emerging fungal pathogens are essential for improving diagnosis and treatment. Sarocladium spinificis, though not widely recognized as a human pathogen, exhibits traits suggesting a potential role in opportunistic infections. This study provides the first detailed morphological, phylogenetic, and genomic characterization of clinical S. spinificis isolates, highlighting its ability to survive at body temperature and its antifungal resistance. Additionally, we demonstrate that these strains inhibit Coccidioides posadasii, the agent of Valley fever, suggesting ecological competition or antifungal properties. These findings contribute to understanding fungal interactions in clinical and environmental settings, with implications for fungal pathogenesis and antifungal strategies. By uncovering new aspects of S. spinificis biology, this work expands knowledge of Sarocladium species in human health and lays the foundation for future research on its ecological role, pathogenic potential, and therapeutic applications.