Evaluation of pathogenesis and biofilm formation ability of Yersinia pestis after 40-day exposure to simulated microgravity

Abstract Background: With the increase of manned space missions and the rise of space microbiology, the research of microbes grown under microgravity environment attracts more attentions. The research scope in space microbiology has been extended beyond pathogens directly related to spaceflight Y. pestis, the causative agent of plague, is also of interest to researchers. Results: After Y. pestis strain 201 cultivated for 40 consecutive passages in either simulated microgravity and normal gravity (NG) conditions, the cultures were used to observe the main phenotypic features of Y. pestis. By using crystal violet staining assays, increased biofilm amount was detected in Y. pestis grown under SMG condition. Besides that, the damage degrees of Hela cell caused by SMG-grown Y. pestis were found diminished in relative to those NG condition. Consistent with this observation, death course was delayed in mice infected with SMG-grown Y. pestis, suggesting that microgravity condition could contribute the attenuated virulence. RNA-seq-based transcriptomics analysis showed a total of 219 genes were differentially regulated, of which 92 upregulated and 127 downregulated. We found dozens of virulence-associated genes were downregulated, which partially explained the reduced virulence of Y. pestis under SMG condition. Our study demonstrated that long-term exposure to simulated microgravity influence the pathogenesis and biofilm formation ability of Y. pestis in a different way, which provides a novel avenue to study the mechanism of physiology and virulence in this pathogen.Conclusions: Microgravity enhanced the ability of biofilm formation of Y. pestis. The virulence and cytotoxicity of Y. pestis were reduced under the microgravity environment. The expressions of many virulence-associated genes of Y. pestis were differentially regulated in response to the stimulated microgravity.