Description and Genome Characterization of Three Novel Fungal Strains Isolated from Mars 2020 Mission-Associated Spacecraft Assembly Facility Surfaces—Recommendations for Two New Genera and One Species

National Aeronautics and Space Administration’s (NASA) spacecraft assembly facilities are monitored for the presence of any bacteria or fungi which might conceivably survive transfer to an extraterrestrial environment. Fungi present a broad and diverse range of phenotypic and functional traits to adapt to extreme conditions, hence detection of fungi and subsequent eradication of them are needed to prevent forward contamination for future NASA missions. During construction and assembly for the Mars 2020 mission, three fungal strains with unique morphological and phylogenetic properties were isolated from spacecraft assembly facilities. The reconstruction of phylogenetic trees based on several gene loci (ITS, LSU, SSU, RPB2, TUB, and TEF1) using multi-locus sequence typing (MLST) and whole genome sequencing (WGS) analyses revealed that these strains were novel. Here we report the genus-level classification of these three novel strains via a polyphasic approach, using phylogenetic analysis, colony and cell morphology, and WGS. The strain FJI-L9-BK-P1 isolated from the Jet Propulsion Laboratory Spacecraft Assembly Facility (JPL-SAF) exhibited a loosely-associated phylogenetic relationship with the strain Aosphaeria arxii CBS175.79 but showed distinct morphology and microscopic features. Another JPL-SAF strain, FJII-L3-CM-DR1, was phylogenetically distinct from members of the family Trichomeriaceae and also exhibited morphologically different features from the genera Lithophyla and Strelitziana. The strain FKI-L1-BK-DR1 isolated from the Kennedy Space Center facility was member of the family Kirschsteiniotheliaceae according to phylogenetic analysis. The polyphasic taxonomic approach supported the recommendation for three novel fungal genera. The names Jayplomyces pasadenensis (FJI-L9-BK-P1T = NRRL B-64424T), Pasadenomyces melaninifex (FJII-L3-CM-DR1T = NRRL B-64433T) and Floridaphiala radiotolerans (FKI-L1-BK-DR1T = NRRL B-64434T) are proposed as holotypes. Furthermore, resistance to Ultraviolet-C (UV-C) and presence of specific biosynthetic gene cluster(s) (BGCs) coding for metabolically active compounds are unique to these strains.

美国国家航空航天局（National Aeronautics and Space Administration，NASA）的航天器组装设施会对可能通过转移存活至外星环境的细菌与真菌开展监测。真菌拥有广泛多样的表型与功能性状以适应极端环境，因此为防范未来NASA任务发生正向污染，需对真菌进行检测并后续根除。在火星2020任务的建造与组装阶段，科研人员从航天器组装设施中分离得到三株具备独特形态与系统发育特性的真菌菌株。通过多位点序列分型（multi-locus sequence typing，MLST）与全基因组测序（whole genome sequencing，WGS）分析，基于ITS、LSU、SSU、RPB2、TUB及TEF1多个基因座重建系统发育树，结果显示这三株菌株均为全新物种。本研究采用结合系统发育分析、菌落与细胞形态学观察以及WGS的多相分类方法，报告了这三株新型菌株的属级分类地位。

从喷气推进实验室航天器组装设施（Jet Propulsion Laboratory Spacecraft Assembly Facility，JPL-SAF）分离得到的菌株FJI-L9-BK-P1，与菌株*Aosphaeria arxii* CBS175.79呈现松散关联的系统发育关系，但二者在形态及显微特征上存在显著差异。另一株JPL-SAF菌株FJII-L3-CM-DR1，在系统发育层面与毛霉科（Trichomeriaceae）成员截然不同，同时其形态特征也与Lithophyla属和Strelitziana属存在明显区别。从肯尼迪航天中心设施分离得到的菌株FKI-L1-BK-DR1，经系统发育分析隶属于Kirschsteiniotheliaceae科。多相分类学方法验证了建立三个新型真菌属的合理性。

本研究提议将三株菌株分别命名为*Jayplomyces pasadenensis*（FJI-L9-BK-P1^T = NRRL B-64424^T）、*Pasadenomyces melaninifex*（FJII-L3-CM-DR1^T = NRRL B-64433^T）及*Floridaphiala radiotolerans*（FKI-L1-BK-DR1^T = NRRL B-64434^T），并指定上述菌株为模式菌株（holotypes）。此外，这些菌株均具备对紫外线C（Ultraviolet-C，UV-C）的抗性，以及编码代谢活性化合物的特异性生物合成基因簇（biosynthetic gene clusters，BGCs），上述特征均为该三株菌株所独有。