title: Increased biofilm formation ability in Klebsiella pneumoniae after short-term exposure to a simulated microgravity environment.
abstract: Biofilm formation is closely related to the pathogenetic processes of Klebsiella pneumoniae, which frequently causes infections in immunocompromised individuals. The immune system of astronauts is compromised in spaceflight. Accordingly, K. pneumoniae, which used to be isolated from orbiting spacecraft and astronauts, poses potential threats to the health of astronauts and mission security. Microgravity is a key environmental cue during spaceflight. Therefore, determining its effects on bacterial biofilm formation is necessary. In this study, K. pneumoniae ATCC BAA-1705 was exposed to a simulated microgravity (SMG) environment. K. pneumoniae grown under SMG formed thicker biofilms compared with those under normal gravity (NG) control after 2 weeks of subculture. Two indicative dyes (i.e., Congo red and calcofluor) specifically binding to cellulose fibers and/or fimbriae were utilized to reconfirm the enhanced biofilm formation ability of K. pneumoniae grown under SMG. Further analysis showed that the biofilms formed by SMG-treated K. pneumoniae were susceptible to cellulase digestion. Yeast cells mannose-resistant agglutination by K. pneumoniae type 3 fimbriae was more obvious in the SMG group, which suggests that cellulose production and type 3 fimbriae expression in K. pneumoniae were both enhanced under the SMG condition. Transcriptomic analysis showed that 171 genes belonging to 15 functional categories were dysregulated in this organism exposed to the SMG conditions compared with those in the NG group, where the genes responsible for the type 3 fimbriae (mrkABCDF) and its regulator (mrkH) were upregulated.
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.
authors.forename: Haili
authors.initials: H
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.
authors.forename: Yanfeng
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Department of Medical Monitoring and Support, Astronaut Center of China, Beijing, 100094, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Rong
authors.affiliation: Animal Husbandry Base Teaching and Research Section, College of Animal Science and Technology, Hebei North University, Zhangjiakou, Hebei, 075131, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.
authors.forename: Hongduo
authors.initials: H
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.
authors.forename: Zizhong
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Medical Monitoring and Support, Astronaut Center of China, Beijing, 100094, China.
authors.forename: Jiaping
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China. ruifuyang@gmail.com.
authors.forename: Ruifu
authors.initials: R
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China. yanpinghan@gmail.com.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Han
mesh_terms: D000371:Agglutination / Q000502:physiology; D018441:Biofilms / Q000254:growth & development*; D002482:Cellulose / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D007711:Klebsiella pneumoniae / Q000254:growth & development* / Q000378:metabolism / Q000472:pathogenicity; D013026:Space Flight; D014893:Weightlessness; D015003:Yeasts / Q000378:metabolism
chemical_list: D002482:Cellulose
keywords: 
  Klebsiella pneumonia
  ; Biofilm; cellulose; simulated microgravity; type 3 fimbriae.