Abstract
BackgroundWith the development of space science, it is important to analyze the relationship between the space environment and genome variations that might cause phenotypic changes in microbes. Klebsiella pneumoniae is commonly found on the human body and is resistant to multiple drugs. To study space-environment-induced genome variations and drug resistance changes, K. pneumoniae was carried into outer space by the Shenzhou VIII spacecraft.ResultsThe K. pneumoniae strain LCT-KP289 was selected after spaceflight based on its phenotypic differences compared to the ground-control strain. Analysis of genomic structural variations revealed one inversion, 25 deletions, fifty-nine insertions, two translocations and six translocations with inversions. In addition, 155 and 400 unique genes were observed in LCT-KP214 and LCT-KP289, respectively, including the gene encoding dihydroxyacetone kinase, which generates the ATP and NADH required for microbial growth. Furthermore, a large number of mutant genes were related to transport and metabolism. Phylogenetic analysis revealed that most genes in these two strains had a dN/dS value greater than 1, indicating that the strain diversity increased after spaceflight. Analysis of drug-resistance phenotypes revealed that the K. pneumoniae strain LCT-KP289 was resistant to sulfamethoxazole, whereas the control strain, LCT-KP214, was not; both strains were resistant to benzylpenicillin, ampicillin, lincomycin, vancomycin, chloramphenicol and streptomycin. The sulfamethoxazole resistance may be associated with sequences in Scaffold7 in LCT-KP289, which were not observed in LCT-K214; this scaffold contained the gene sul1. In the strain LCT-KP289, we also observed a drug-resistance integron containing emrE (confers multidrug resistance) and ant (confers resistance to spectinomycin, streptomycin, tobramycin, kanamycin, sisomicin, dibekacin, and gentamicin). The gene ampC (confers resistance to penicillin, cephalosporin-ii and cephalosporin-i) was present near the integron. In addition, 30 and 26 drug-resistance genes were observed in LCT-KP289 and LCT-KP214, respectively.ConclusionsComparison of a K. pneumoniae strain obtained after spaceflight with the ground-control strain revealed genome variations and phenotypic changes and elucidated the genomic basis of the acquired drug resistance. These data pave the way for future studies on the effects of spaceflight.
Highlights
With the development of space science, it is important to analyze the relationship between the space environment and genome variations that might cause phenotypic changes in microbes
Many clinical strains of K. pneumoniae are highly resistant to antibiotics, which poses a major threat to global public health
The genomes of LCT-KP289 and LCT-KP214 were sequenced to compare their genomic variations. These analyses revealed genes potentially related to drug resistance, and analysis of the putative drug-resistance genes revealed variations in the homologous genes in the two strains
Summary
With the development of space science, it is important to analyze the relationship between the space environment and genome variations that might cause phenotypic changes in microbes. To study space-environment-induced genome variations and drug resistance changes, K. pneumoniae was carried into outer space by the Shenzhou VIII spacecraft. Space environmental physics has elucidated the existence of properties including electromagnetic radiation, microgravity, high vacuum and strong magnetic field in the space environment; it is important to understand the impact of these factors on organisms. Tixador et al studied the growth and antibiotic resistance of Escherichia coli during the mission of the space shuttle Discovery [6]. Mutations caused by the space environment have not been examined at the genomic level. The effect of spaceflight on K. pneumoniae has not been examined at the genomic level. K. pneumoniae is well-suited for such studies because of its characteristics
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