Link to the paper: https://imafungus.biomedcentral.com/…/s43008-023-00119-4

This paper describes the isolation and characterization of two novel fungal strains, Naganishia kalamii and Cystobasidium onofrii, from the Mars 2020 mission assembly facilities. The strains were identified using a combination of traditional morphology methods, phylogenetic analysis, and whole genome sequencing. The genomic analysis revealed proteins associated with stress-response and genes related to osmotolerance and psychrotolerance in both strains. Additionally, both N. kalamii and C. onofrii showed resistance to UV-C radiation, highlighting their potential importance in NASA’s planetary protection programs.

Cystobasidium onofrii can be differentiated from other Cystobasidium species based on its darker pink to orange-colored colonies and its ability to grow in medium supplemented with 5 NaCl. Fungal-specific transcriptional factors were found to be more prominent in C. onofrii compared to strains isolated from natural extreme environments.

The practical implications of this paper are:

This paper contributes to the field of astrobiology by describing the isolation and characterization of two novel fungal strains, Naganishia kalamii and Cystobasidium onofrii, from the Mars 2020 mission assembly facilities.

The paper employs a polyphasic taxonomic approach, combining traditional morphology methods, phylogenetic analysis, and whole genome sequencing, to accurately identify and classify the two novel strains.

The genomic analysis of these strains reveals proteins associated with stress-response and genes related to osmotolerance and psychrotolerance, providing insights into their ability to survive in extreme environments.

The study also highlights the importance of studying extremotolerant microbes, including yeasts, for NASA’s planetary protection programs, as both N. kalamii and C. onofrii showed resistance to UV-C radiation.

This research expands our understanding of microbial diversity and adaptation to extreme conditions, which is crucial for future space exploration missions.

Practical implications

The practical implications of this paper include the need for more precise identification techniques like MLSA and WGS for accurately classifying complex yeast genera like Naganishia, as traditional methods are deemed inadequate.

The study highlights the potential risk of UV-C resistant yeasts, including N. kalamii and C. onofrii, contaminating extraterrestrial environments and posing risks to life-detection missions.

The presence of these cold-adapted yeasts in NASA cleanrooms raises concerns for future missions to icy moons, emphasizing the importance of understanding their survival capabilities in harsh conditions.

The genomic analysis of N. kalamii and C. onofrii reveals proteins associated with stress-response and genes related to osmotolerance and psychrotolerance, providing insights into their ability to withstand extreme environments.

The UV resistance of both novel species emphasizes the need for collecting and characterizing extremotolerant microbes, including yeasts, to improve microbial reduction techniques used in NASA’s planetary protection programs.

The methods used in this paper are:

The methods used in this paper include traditional colony and cell morphology methods, multi-locus sequence analysis (MLSA) based on several gene loci (ITS, LSU, SSU, RPB1, RPB2, CYTB, and TEF1), and whole genome sequencing (WGS) for the characterization and classification of the two novel fungal strains.

Phylogenomic trees were constructed using the PHYling pipeline and protein models representing the Tremellomycetes class and Cystobasidiales order were downloaded from the Mycocosm portal for phylogenetic analysis.

Multi-locus phylogenetic analyses were performed using seven genes (ITS, LSU, SSU, RPB1, RPB2, CYTB, and TEF1) to obtain solid placement of the two yeast strains.

The alignment of gene sequences and construction of phylogenetic trees were carried out using the R package DECIPHER and IQ-TREE, respectively.

The survivability of the yeasts after exposure to UV-C radiation was assessed, and the number of viable cells was measured.

Data used in the study

The data used in this paper includes the isolation and characterization of two novel fungal strains from NASA cleanrooms, namely Naganishia kalamii and Cystobasidium onofrii.

Traditional colony and cell morphology methods were used to initially characterize the strains, followed by multi-locus sequence analysis (MLSA) based on several gene loci (ITS, LSU, SSU, RPB1, RPB2, CYTB, and TEF1) for phylogenetic reconstructions.

Whole genome sequencing (WGS) was also performed to support the species-level classification and to analyze the genomic characteristics of the two yeasts.

Comparative genomic analysis was conducted to identify proteins associated with stress-response, genes related to osmotolerance and psychrotolerance, and the presence of genes associated with dehydration, desiccation, rehydration, and UV resistance.

The survivability of the yeasts after exposure to UV-C radiation was assessed, and the number of viable cells was measured.

The results of this paper are:

The paper presents the genomic characterization and radiation tolerance of two novel fungal strains, Naganishia kalamii and Cystobasidium onofrii, isolated from NASA cleanrooms during the construction and assembly of the Mars 2020 mission components.

The species-level classification of these strains was determined using traditional colony and cell morphology methods, as well as multi-locus sequence analysis (MLSA) based on several gene loci and whole genome sequencing (WGS).

The phylogenetic analyses based on MLSA and WGS supported the conclusion that N. kalamii belongs to the Naganishia albida clade, while C. onofrii belongs to the genus Cystobasidium.

The genomic analysis revealed proteins associated with dehydration and desiccation stress-response, as well as genes related to osmotolerance and psychrotolerance in both yeasts.

Both N. kalamii and C. onofrii showed resistance to UV-C radiation, highlighting the importance of studying extremotolerant microbes for NASA’s planetary protection programs.

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