Leo Patrick, de Melo Texeira Marcus, Chander Atul M, Singh Nitin K, Simpson Anna C, Yurkov Andrey, Karouia Fathi, Stajich Jason E, Mason Christopher E, Venkateswaran Kasthuri
Department of Environmental Sciences, Informatics and Statistics, University Ca' Foscari of Venice, Via Torino 155, 30172, Mestre, Italy.
Department of Ecological and Biological Sciences, University of Tuscia, Largo dell'università snc, 01100, Viterbo, Italy.
IMA Fungus. 2023 Aug 11;14(1):15. doi: 10.1186/s43008-023-00119-4.
During the construction and assembly of the Mars 2020 mission components at two different NASA cleanrooms, several fungal strains were isolated. Based on their colony morphology, two strains that showed yeast-like appearance were further characterized for their phylogenetic position. The species-level classification of these two novel strains, using traditional colony and cell morphology methods combined with the phylogenetic reconstructions using multi-locus sequence analysis (MLSA) based on several gene loci (ITS, LSU, SSU, RPB1, RPB2, CYTB and TEF1), and whole genome sequencing (WGS) was carried out. This polyphasic taxonomic approach supported the conclusion that the two basidiomycetous yeasts belong to hitherto undescribed species. The strain FJI-L2-BK-P3, isolated from the Jet Propulsion Laboratory Spacecraft Assembly Facility, was placed in the Naganishia albida clade (Filobasidiales, Tremellomycetes), but is genetically and physiologically different from other members of the clade. Another yeast strain FKI-L6-BK-PAB1, isolated from the Kennedy Space Center Payload Hazardous and Servicing Facility, was placed in the genus Cystobasidium (Cystobasidiales, Cystobasidiomycetes) and is distantly related to C. benthicum. Here we propose two novel species with the type strains, Naganishia kalamii sp. nov. (FJI-L2-BK-P3 = NRRL 64466 = DSM 115730) and Cystobasidium onofrii sp. nov. (FKI-L6-BK-PAB1 = NRRL 64426 = DSM 114625). The phylogenetic analyses revealed that single gene phylogenies (ITS or LSU) were not conclusive, and MLSA and WGS-based phylogenies were more advantageous for species discrimination in the two genera. The genomic analysis predicted proteins associated with dehydration and desiccation stress-response and the presence of genes that are directly related to osmotolerance and psychrotolerance in both novel yeasts described. Cells of these two newly-described yeasts were exposed to UV-C radiation and compared with N. onofrii, an extremophilic UV-C resistant cold-adapted Alpine yeast. Both novel species were UV resistant, emphasizing the need for collecting and characterizing extremotolerant microbes, including yeasts, to improve microbial reduction techniques used in NASA planetary protection programs.
在美国国家航空航天局（NASA）的两个不同洁净室对“火星2020”任务组件进行建造和组装期间，分离出了几种真菌菌株。根据其菌落形态，对表现出酵母样外观的两种菌株进一步确定其系统发育位置。使用传统的菌落和细胞形态学方法，结合基于多个基因座（ITS、LSU、SSU、RPB1、RPB2、CYTB和TEF1）的多位点序列分析（MLSA）以及全基因组测序（WGS），对这两种新菌株进行了物种水平分类。这种多相分类方法支持了这两种担子菌酵母属于迄今未描述物种的结论。从喷气推进实验室航天器组装设施分离出的菌株FJI-L2-BK-P3，被归入白色纳氏酵母分支（丝孢酵母目，银耳菌纲），但在遗传和生理上与该分支的其他成员不同。另一种酵母菌株FKI-L6-BK-PAB1，从肯尼迪航天中心有效载荷危险与服务设施分离得到，被归入囊肿担子菌属（囊肿担子菌目，囊肿担子菌纲），与底栖囊肿担子菌亲缘关系较远。在此，我们提出两个新物种及其模式菌株，即卡拉姆纳氏酵母新种（FJI-L2-BK-P3 = NRRL 64466 = DSM 115730）和奥诺弗里囊肿担子菌新种（FKI-L6-BK-PAB1 = NRRL 64426 = DSM 114625）。系统发育分析表明，单基因系统发育（ITS或LSU）并不具有决定性，基于MLSA和WGS的系统发育对于这两个属的物种鉴别更具优势。基因组分析预测了与脱水和干燥应激反应相关的蛋白质，以及在所描述的两种新酵母中与耐渗透压和耐冷性直接相关的基因的存在。将这两种新描述酵母的细胞暴露于UV-C辐射下，并与嗜极端环境的耐UV-C且适应寒冷的高山酵母奥诺弗里酵母进行比较。这两个新物种均具有抗UV能力，强调了收集和鉴定包括酵母在内的耐极端微生物以改进NASA行星保护计划中使用的微生物减少技术的必要性。
