Wallemia orionensis sp. nov., a Xerophilic and Halotolerant Fungus Isolated from Air Environment.

A novel xerophilic fungus, Wallemia orionensis sp. nov., was isolated from air samples collected in a cake production environment and is described here based on a polyphasic approach, including molecular phylogenetics, morphology, and physiological traits. Phylogenetic analyses using concatenated ITS and SSU rDNA sequences revealed that the three strains form a distinct and well-supported clade within the genus Wallemia, clearly separated from all currently recognized species. Colonies of W. orionensis exhibit slow to moderate growth on media supplemented with high concentrations of glucose or sodium chloride, but fail to grow on media lacking such solutes, confirming its obligate xerophilic nature. The species demonstrates remarkable halotolerance and osmophily, growing optimally in media containing 50% glucose or 10-17% NaCl. Microscopic examination reveals that it exhibits the characteristic morphological features of the genus Wallemia, with arthroconidia formed by the fragmentation of hyphae, appearing as short cylindrical, barrel-shaped, or bluntly rounded structures. The isolation of W. orionensis from air samples in a cake production environment expands the known diversity of the genus Wallemia and contributes to a better understanding of fungal adaptation to high-solute, low-water-activity conditions.