Study On The Effects And Mechanisms Of Simulated Microgravity On Stenotrophomonas Maltophilia

Background and Objective: With the aerospace industry booming,the world powers are competing in space.The International Space Station,which was established in the late 2000 s,is currently the main place to carry out researches.China will have completed the construction of the Chinese orbiting space station around 2022.Recently,three taikonauts aboard the Shenzhou XIII spacecraft will carry out a six-month space mission,and long-term confined missions will gradually become the norm in the future.Previous studies have shown that microbial strains have been isolated from environmental samples in the International Space Station,and some bacteria showed tolerance to extreme environmental variability,which posed some threats to the safety of astronauts.It was found that the space environment affects the viability,growth characteristics,drug resistance,virulence,biochemical metabolism,motility and biofilm formation ability of microorganisms.In the confined space capsule,cosmic rays as well as extreme temperature are relatively limited,so microgravity becomes a key factor that has a greater impact on microorganisms,and therefore we consider the simulated microgravity as the springboard for experimental design.Stenotrophomonas maltophilia(S.maltophilia),as a type of conditional pathogen with a gradual increase in clinical morbidity more recently,is prone to infect patient in hypoimmunity and is difficult to treat.The research of S.maltophilia in space environment has rarely been reported yet.Astronauts were exposed to long-term space environment,and their body functions,metabolism and immunity were degraded.As a result,the research of environmental adaption studies on S.maltophilia under extreme conditions could provide astronauts with infection prevention and treatment strategies.Methods : In this study,S.maltophilia was exposed to a simulated microgravity environment in high-aspect ratio rotating-wall vessels bioreactors for 14 days,while the control group was performed in the same bioreactors under normal gravity environment.Then,the growth characteristics,drug resistance,biofilm detection,motility,and biochemical metabolism were compared.After that,we analyzed the data in combination with the phenotype,genome,transcriptome and proteome,compared the differences in the physiological properties of S.maltophilia under simulated microgravity and normal gravity conditions and explored the molecular mechanisms.Results: It was founded that the S.maltophilia in simulated microgravity(SMS)displayed increased growth rate and motility,enhanced biofilm formation ability,as well as some metabolism alterations compared with the S.maltophilia in normal gravity(SMN)and the original strain of S.maltophilia(SMO).The COG annotation analysis of genome indicated that the increased growth rate might be related to upregulated differentially expressed genes(DEGs)involved in secondary metabolites biosynthesis,energy metabolism and conversion,intracellular trafficking,transport and catabolism,secretion and vesicular transport.The GO and KEGG enrichment analysis of proteome showed that the increased motility might be associated with upregulated differentially expressed proteins(DEPs)involved in locomotion,localization,biological adhesion and binding.These changes were also in accordance with upregulated DEGs in cell motility by COG classification,including pil P,pil M,flg E,flg G and ron N.The GO and KEGG enrichment analysis of proteome revealed that the increased biofilm formation ability might be associated with upregulated DEPs involved in biofilm formation,bacterial secretion system,biological adhesion and cell adhesion.An integration of transcriptomic and proteomic analysis showed that the increased biofilm formation ability was driven by the DEGs,including the chp B,chp C,rpo N,pil A,pil G,pil H,and pil J.Conclusion : These results suggested that simulated microgravity might increase the level of corresponding functional proteins by upregulating the genes related to cell motility,intracellular trafficking,vesicular transport,energy production,energy conversion,secretion function,and biofilm formation.Thus,followed by alteration of some physiological characteristics and affecting the growth rate,motility,biofilm formation and metabolism.In conclusion,our study provides an overall analysis of genomic,transcriptomic,proteomic,and phenotypic changes in S.maltophilia under simulated microgravity and will provide some suggestions for future study of space microbiology.