The Preliminary Study Of Bacillus Cereus After Spaceflight

Aims:The space environment has the characteristic of weightlessness, vacuum, micro magnetic fields and particle radiation, which can affect microbial biology morphological and phenotypic changes. In this study, Bacillus cereus was sent into space by the Shenzhou VIII spacecraft. When Bacillus cereus came back to Earth, the phenotype was performed in order to find how Bacillus cereus changed in the space environment. After that, genomics, transcriptome, and proteomics were used to reveal the relevant mechanism after spaceflight.Methods:When Bacillus cereus came back to Earth, morphology, strain identification, antibiotic resistance, hemolysis, the spectrum of biochemical metabolic and growth rates were performed in order to find how Bacillus cereus changed in the space environment. High-throughput Illumina sequencing technology was used to sequence the spaceflight stains and the ground control stain. The comparative genomics analysis was performed to explore the difference between spaceflight Bacillus cereus strains and ground control strain, including evolutionary analysis, collinearity and rearrangement analysis, plasmid identification and variance analysis, SNP analysis and comment, InDel difference analysis and comment, Core Pan analysis. The transcriptome sequencing and proteomics were performed to screen the differentiate expressed genes and/or proteins. GO, COG and KEGG functional analysis were used to annotate these genes and/or proteins. Clustering analyze and enrichment analysis were also performed to find which function is the most important during the space flight. Finally, the trans-omics analysis was performed.Results:The Shenzhou VIII unmanned spacecraft successfully equipped with Bacillus cereus with the survival rate100%. Morphology and hemolytic properties of Bacillus cereus did not change after space flight. Compare with the ground control group LCT-BC244and mutant strain LCT-BC235, the mutant strain LCT-BC25enhanced resistance to amikacin; whereas two strains of spaceflight had significant changes in biochemical metabolic and decreased growth rate. Based on the phylogenetic analysis, we found Bacillus cereus LCT-BC244, LCT-BC25and LCT-BC235homology with Bacillus AH187, which contained induced vomiting virulence genes. However, the genome of LCT-BC25and LCT-BC235had no significantly changed compared with LCT-BC244, according to linear analysis. Plasmid analysis found that the plasmid of LCT-BC25and LCT-BC235are less than the ground control strain after space flight. Core Pan analysis revealed that seven specific genes existed in this plsmid. In addition, space flight Bacillus cereus LCT-BC25and LCT-BC235had three SNP loci respectively. Transcriptome showed that there are more than a thousand genes differentially expressed genes after spaceflight. According to the COG analysis, we found that the main changes of these two spaceflight strains focused on transport and metabolism. Functional analysis of differentially expressed genes found that upregulated or downregulated genes are affected by environmental factors. That is to say, the common cause of the changes of these two strains was ion transporter. The unusual expression of genes reflect the impact of differences in bacterial morphology and structure, which affect the growth. The specific expressed genes of these two strain mainly reflects differences in metabolism, which showed that undirected mutagenesis--bacterial metabolic mechanisms adapt to changes by the space environment. Proteomics analysis demonstrated that1067proteins were identified. These proteins were metabolism-related based on functional analysis. Although under the same spatial exposure conditions and the differentially expressed genes are all belonged to metabolism, the expression levels of these proteins associated metabolic changes were not the same, which revealed that the influence of environmental factors were uncertain. Transcriptome and proteome meta-analysis found that the differentially genes and proteins in two spaceflight strains were concentrated in the metabolism changes.Conclusions:Our study represents the first documented analysis of the combination of phenotypic, genomic, transcriptomic, and proteomic changes that occur in Bacillus cereus during space flight. These results demonstrate that fragment loss and changes in metabolism, structure and virulence are influenced by the space environment. What is the value of the changes of Bacillus cereus after spaceflight remains to be seen and is a future area of investigation. Research on the effects of the space environment on microorganisms will continue to be a vital component of manned space exploration and will benefit space microbiology.