title: Low gravity and inertial effects on the growth of E. coli and B. subtilis in semi-solid media.
abstract: BACKGROUND
  Several published experimental results have shown that cultures of suspended bacteria exhibit increased growth in the spaceflight environment. HYPOTHESIS AND METHODS: To test whether these differences were due to fluid mechanics and not cellular effects, E. coli and B. subtilis were grown on agar cultures under static, agitated, and rotated conditions in the laboratory, and under low-gravity conditions on four Space Shuttle flights. Growth experiments were terminated with glutaraldehyde, and individual cells were counted after quantitative elution from the agar.
  
  
  RESULTS
  The spaceflight results, in conjunction with static, rotation, and agitation experiments indicate that E. coli and B. subtilis cultures on agar, unlike their suspension grown counterparts, do not experience heightened final cell concentration when the inertial environment is changed.
  
  
  CONCLUSIONS
  This finding points to fluid dynamics and extracellular transport phenomena and not cellular dynamics as the most likely cause of previously reported increases in bacterial growth in microgravity.
authors.affiliation: Department of Aerospace Engineering Sciences, University of Colorado, Boulder, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Kacena
authors.forename: P E
authors.initials: PE
authors.lastname: Leonard
authors.forename: P
authors.initials: P
authors.lastname: Todd
authors.forename: M W
authors.initials: MW
authors.lastname: Luttges
mesh_terms: D001412:Bacillus subtilis / Q000254:growth & development*; D003470:Culture Media; D004926:Escherichia coli / Q000254:growth & development*; D013026:Space Flight; D014893:Weightlessness
chemical_list: D003470:Culture Media