Phenotypic and genomic comparison of spaceflight-relevant Staphylococcus capitis

Kurzfassung

Previous studies have reported that spaceflight-specific conditions such as microgravity can lead to changes in bacterial physiology and resistance behavior, including increased expression of virulence factors and biofilm formation, and decreased susceptibility to antibiotics. We compared three spaceflight-relevant Staphylococcus capitis strains (DSM 111179, International Space Station (ISS); DSM 31028, clean room; DSM 113836; artificial gravity bed rest study) to the type strain (DSM 20326T) to investigate spaceflight-induced physiological and genomic changes. The strains were tested for growth, colony morphology, metabolism, fatty acid and polar lipid patterns, biofilm formation and susceptibility to antibiotics. Furthermore, we tested survival under various stress conditions such as treatment with hydrogen peroxide, desiccation, irradiation with X-rays, and UV-C. We examined the genomes of all four strains for possible genetic determinants of the phenotypic differences. In general, we found that all four strains had similar metabolic patterns, the same sensitivity to antibiotics, and similar radiation tolerance. Physiological differences were observed mainly compared to the type strain and minor differences between the other three strains. The strain isolated from the ISS and the strain isolated from the bed rest study exhibited delayed yellow pigmentation, which is absent in the other two strains. The phenotypic and genomic differences between the strains observed in this study do not indicate increased virulence of the spaceflight isolate. However, the enhanced growth rate, higher weighted average melting temperature of the fatty acid profile, and colony pigmentation of the spaceflight isolate are relevant phenotypes that need to be further explored in the context of human spaceflight.