title: Responses of haloarchaea to simulated microgravity.
abstract: Various effects of microgravity on prokaryotes have been recognized in recent years, with the focus on studies of pathogenic bacteria. No archaea have been investigated yet with respect to their responses to microgravity. For exposure experiments on spacecrafts or on the International Space Station, halophilic archaea (haloarchaea) are usually embedded in halite, where they accumulate in fluid inclusions. In a liquid environment, these cells will experience microgravity in space, which might influence their viability and survival. Two haloarchaeal strains, Haloferax mediterranei and Halococcus dombrowskii, were grown in simulated microgravity (SMG) with the rotary cell culture system (RCCS, Synthecon). Initially, salt precipitation and detachment of the porous aeration membranes in the RCCS were observed, but they were avoided in the remainder of the experiment by using disposable instead of reusable vessels. Several effects were detected, which were ascribed to growth in SMG: Hfx. mediterranei's resistance to the antibiotics bacitracin, erythromycin, and rifampicin increased markedly; differences in pigmentation and whole cell protein composition (proteome) of both strains were noted; cell aggregation of Hcc. dombrowskii was notably reduced. The results suggest profound effects of SMG on haloarchaeal physiology and cellular processes, some of which were easily observable and measurable. This is the first report of archaeal responses to SMG. The molecular mechanisms of the effects induced by SMG on prokaryotes are largely unknown; haloarchaea could be used as nonpathogenic model systems for their elucidation and in addition could provide information about survival during lithopanspermia (interplanetary transport of microbes inside meteorites).
authors.affiliation: Department of Microbiology, Division of Molecular Biology, University of Salzburg, Austria.
authors.forename: Marion
authors.initials: M
authors.lastname: Dornmayr-Pfaffenhuemer
authors.forename: Andrea
authors.initials: A
authors.lastname: Legat
authors.forename: Karin
authors.initials: K
authors.lastname: Schwimbersky
authors.forename: Sergiu
authors.initials: S
authors.lastname: Fendrihan
authors.forename: Helga
authors.initials: H
authors.lastname: Stan-Lotter
mesh_terms: D002449:Cell Aggregation; D018929:Cell Culture Techniques; D004352:Drug Resistance, Microbial; D019625:Halococcus / Q000502:physiology*; D019623:Haloferax mediterranei / Q000502:physiology*; D010858:Pigmentation; D020543:Proteome; D014893:Weightlessness
chemical_list: D020543:Proteome