Identification of staphyloxanthin and derivates in yellow-pigmented Staphylococcus capitis subsp. capitis.

Introduction: Staphylococcus capitis naturally colonizes the human skin but as an opportunistic pathogen, it can also cause biofilm-associated infections and bloodstream infections in newborns. Previously, we found that two strains from the subspecies S. capitis subsp. capitis produce yellow carotenoids despite the initial species description, reporting this subspecies as non-pigmented. In Staphylococcus aureus, the golden pigment staphyloxanthin is an important virulence factor, protecting cells against reactive oxygen species and modulating membrane fluidity. Methods: In this study, we used two pigmented (DSM 111179 and DSM 113836) and two non-pigmented S. capitis subsp. capitis strains (DSM 20326T and DSM 31028) to identify the pigment, determine conditions under which pigment-production occurs and investigate whether pigmented strains show increased resistance to ROS and temperature stress. Results: We found that the non-pigmented strains remained colorless regardless of the type of medium, whereas intensity of pigmentation in the two pigmented strains increased under low nutrient conditions and with longer incubation times. We were able to detect and identify staphyloxanthin and its derivates in the two pigmented strains but found that methanol cell extracts from all four strains showed ROS scavenging activity regardless of staphyloxanthin production. Increased survival to cold temperatures (-20°C) was detected in the two pigmented strains only after long-term storage compared to the non-pigmented strains. Conclusion: The identification of staphyloxanthin in S. capitis is of clinical relevance and could be used, in the same way as in S. aureus, as a possible target for anti-virulence drug design.

Phenotypic and genomic assessment of the potential threat of human spaceflight-relevant Staphylococcus capitis isolates under stress conditions.

Previous studies have reported that spaceflight specific conditions such as microgravity lead to changes in bacterial physiology and resistance behavior including increased expression of virulence factors, enhanced biofilm formation and decreased susceptibility to antibiotics. To assess if spaceflight induced physiological changes can manifest in human-associated bacteria, we compared three spaceflight relevant Staphylococcus capitis isolates (DSM 111179, ISS; DSM 31028, clean room; DSM 113836; artificial gravity bedrest study) with the type strain (DSM 20326T). We tested the three strains regarding growth, colony morphology, metabolism, fatty acid and polar lipid pattern, biofilm formation, susceptibility to antibiotics and survival in different stress conditions such as treatment with hydrogen peroxide, exposure to desiccation, and irradiation with X-rays and UV-C. Moreover, we sequenced, assembled, and analyzed the genomes of all four strains. Potential genetic determinants for phenotypic differences were investigated by comparative genomics. We found that all four strains show similar metabolic patterns and the same susceptibility to antibiotics. All four strains were considered resistant to fosfomycin. Physiological differences were mainly observed compared to the type strain and minor differences among the other three strains. The ISS isolate and the bedrest study isolate exhibit a strong delayed yellow pigmentation, which is absent in the other two strains. Pigments were extracted and analyzed by UV/Vis spectroscopy showing characteristic carotenoid spectra. The ISS isolate showed the highest growth rate as well as weighted average melting temperature (WAMT) of fatty acids (41.8°C) of all strains. The clean room isolate showed strongest biofilm formation and a high tolerance to desiccation. In general, all strains survived desiccation better in absence of oxygen. There were no differences among the strains regarding radiation tolerance. Phenotypic and genomic differences among the strains observed in this study are not inevitably indicating an increased virulence of the spaceflight isolate. However, the increased growth rate, higher WAMT and colony pigmentation of the spaceflight isolate are relevant phenotypes that require further research within the human spaceflight context. We conclude that combining genetic analysis with classical microbiological methods allows the detailed assessment of the potential threat of bacteria in highly regulated and extreme environments such as spaceflight environments.

Spaceflight Virology: What Do We Know about Viral Threats in the Spaceflight Environment?

Viruses constitute a significant part of the human microbiome, so wherever humans go, viruses are brought with them, even on space missions. In this mini review, we focus on the International Space Station (ISS) as the only current human habitat in space that has a diverse range of viral genera that infect microorganisms from bacteria to eukaryotes. Thus, we have reviewed the literature on the physical conditions of space habitats that have an impact on both virus transmissibility and interaction with their host, which include UV radiation, ionizing radiation, humidity, and microgravity. Also, we briefly comment on the practices used on space missions that reduce virus spread, that is, use of antimicrobial surfaces, spacecraft sterilization practices, and air filtration. Finally, we turn our attention to the health threats that viruses pose to space travel. Overall, even though efforts are taken to ensure safe conditions during human space travel, for example, preflight quarantines of astronauts, we reflect on the potential risks humans might be exposed to and how those risks might be aggravated in extraterrestrial habitats.

MARSBOx: Fungal and Bacterial Endurance From a Balloon-Flown Analog Mission in the Stratosphere.

Whether terrestrial life can withstand the martian environment is of paramount interest for planetary protection measures and space exploration. To understand microbial survival potential in Mars-like conditions, several fungal and bacterial samples were launched in September 2019 on a large NASA scientific balloon flight to the middle stratosphere (∼38 km altitude) where radiation levels resembled values at the equatorial Mars surface. Fungal spores of Aspergillus niger and bacterial cells of Salinisphaera shabanensis, Staphylococcus capitis subsp. capitis, and Buttiauxella sp. MASE-IM-9 were launched inside the MARSBOx (Microbes in Atmosphere for Radiation, Survival, and Biological Outcomes Experiment) payload filled with an artificial martian atmosphere and pressure throughout the mission profile. The dried microorganisms were either exposed to full UV-VIS radiation (UV dose = 1148 kJ m-2) or were shielded from radiation. After the 5-h stratospheric exposure, samples were assayed for survival and metabolic changes. Spores from the fungus A. niger and cells from the Gram-(-) bacterium S. shabanensis were the most resistant with a 2- and 4-log reduction, respectively. Exposed Buttiauxella sp. MASE-IM-9 was completely inactivated (both with and without UV exposure) and S. capitis subsp. capitis only survived the UV shielded experimental condition (3-log reduction). Our results underscore a wide variation in survival phenotypes of spacecraft associated microorganisms and support the hypothesis that pigmented fungi may be resistant to the martian surface if inadvertently delivered by spacecraft missions.