Researchers at Queen's University of Belfast isolated a new yeast species, Rhodotorula nitens, from an atmospheric settling plate in Edinburgh. The organism was characterized using standard microbiological methods and compared to existing Rhodotorula species. R. nitens is a capsulated, orange-colored yeast notable for its marked preference for low temperatures, with optimal growth between 12-16°C and inability to grow above 26°C. The yeast does not ferment sugars but assimilates glucose, galactose, sucrose, maltose, and lactose. It produces carotenoid pigments including β-carotene and γ-carotene, and requires thiamine with partial dependence on calcium pantothenate. The organism grows across a wide pH range (2.2-8, optimum ~5) and lacks pseudomycelium formation. While R. nitens resembles Rhodotorula flava in biochemical properties, it differs in cell morphology, colony appearance, orange pigmentation, and notably its low-temperature optimum and heat sensitivity. The authors discuss taxonomic challenges in distinguishing Rhodotorula from related genera, as traditional criteria like carotenoid pigmentation and starch formation show inconsistent distributions among species.

Key findings

• Rhodotorula nitens is a new yeast species isolated from atmosphere with a distinctive capsule and orange coloration
• The organism exhibits marked psychrophilia with optimal growth at 12-16°C and extreme heat intolerance, being killed at 37°C within 8-10 hours
• R. nitens requires thiamine and shows partial requirement for calcium pantothenate, assimilates multiple hexose and disaccharide sugars but cannot ferment them
• The yeast produces carotenoid pigments (β-carotene and γ-carotene) and grows across pH 2.2-8 with optimum around pH 5
• R. nitens resembles Rhodotorula flava biochemically but differs in morphology, colony appearance, and temperature preferences