title: Effects of simulated microgravity on Streptococcus mutans physiology and biofilm structure.
abstract: Long-term spaceflights will eventually become an inevitable occurrence. Previous studies have indicated that oral infectious diseases, including dental caries, were more prevalent in astronauts due to the effect of microgravity. However, the impact of the space environment, especially the microgravity environment, on the virulence factors of Streptococcus mutans, a major caries-associated bacterium, is yet to be explored. In the present study, we investigated the impact of simulated microgravity on the physiology and biofilm structure of S. mutans. We also explored the dual-species interaction between S. mutans and Streptococcus sanguinis under a simulated microgravity condition. Results indicated that the simulated microgravity condition can enhance the acid tolerance ability, modify the biofilm architecture and extracellular polysaccharide distribution of S. mutans, and increase the proportion of S. mutans within a dual-species biofilm, probably through the regulation of various gene expressions. We hypothesize that the enhanced competitiveness of S. mutans under simulated microgravity may cause a multispecies micro-ecological imbalance, which would result in the initiation of dental caries. Our current findings are consistent with previous studies, which revealed a higher astronaut-associated incidence of caries. Further research is required to explore the detailed mechanisms.
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Xingqun
authors.initials: X
authors.lastname: Cheng
authors.forename: Xin
authors.initials: X
authors.lastname: Xu
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
authors.forename: Lei
authors.initials: L
authors.lastname: Cheng
authors.forename: Mingyun
authors.initials: M
authors.lastname: Li
authors.forename: Jiyao
authors.initials: J
authors.lastname: Li
authors.forename: Renke
authors.initials: R
authors.lastname: Wang
authors.forename: Wenxiang
authors.initials: W
authors.lastname: Jia
authors.forename: Yu-Qing
authors.initials: YQ
authors.lastname: Li
mesh_terms: D000898:Antibiosis; D018441:Biofilms / Q000254:growth & development*; D006801:Humans; D013295:Streptococcus mutans / Q000254:growth & development / Q000502:physiology*; D013298:Streptococcus sanguis / Q000254:growth & development / Q000502:physiology; D014893:Weightlessness
keywords: acid tolerance; astronauts; biofilm architecture; dental caries; interspecies competition; mutacin production