title: Exposure of phototrophs to 548 days in low Earth orbit: microbial selection pressures in outer space and on early earth.
abstract: An epilithic microbial community was launched into low Earth orbit, and exposed to conditions in outer space for 548 days on the European Space Agency EXPOSE-E facility outside the International Space Station. The natural phototroph biofilm was augmented with akinetes of Anabaena cylindrica and vegetative cells of Nostoc commune and Chroococcidiopsis. In space-exposed dark controls, two algae (Chlorella and Rosenvingiella spp.), a cyanobacterium (Gloeocapsa sp.) and two bacteria associated with the natural community survived. Of the augmented organisms, cells of A. cylindrica and Chroococcidiopsis survived, but no cells of N. commune. Only cells of Chroococcidiopsis were cultured from samples exposed to the unattenuated extraterrestrial ultraviolet (UV) spectrum (>110 nm or 200 nm). Raman spectroscopy and bright-field microscopy showed that under these conditions the surface cells were bleached and their carotenoids were destroyed, although cell morphology was preserved. These experiments demonstrate that outer space can act as a selection pressure on the composition of microbial communities. The results obtained from samples exposed to >200 nm UV (simulating the putative worst-case UV exposure on the early Earth) demonstrate the potential for epilithic colonization of land masses during that time, but that UV radiation on anoxic planets can act as a strong selection pressure on surface-dwelling organisms. Finally, these experiments have yielded new phototrophic organisms of potential use in biomass and oxygen production in space exploration.
authors: CEPSAR, Open University, Milton Keynes, UK. c.s.cockell@open.aac.uk
authors: Charles S
authors: CS
authors: Cockell
authors: Petra
authors: P
authors: Rettberg
authors: Elke
authors: E
authors: Rabbow
authors: Karen
authors: K
authors: Olsson-Francis
references: Appl Environ Microbiol. 1992 Oct;58(10):3413-6
references: 1444376
references: J Cell Sci. 1981 Jun;49:341-52
references: 6796596
references: Astrobiology. 2009 Mar;9(2):229-40
references: 19371163
references: Science. 2007 Sep 28;317(5846):1903-6
references: 17901330
references: Astrobiology. 2005 Apr;5(2):127-40
references: 15815164
references: Orig Life Evol Biosph. 1993 Feb;23(1):37-52
references: 8433836
references: Appl Environ Microbiol. 2000 Apr;66(4):1489-92
references: 10742231
references: Environ Microbiol. 2006 Dec;8(12):2201-13
references: 17107561
references: Icarus. 2003 Oct;165(2):253-76
references: 14649627
references: Plant Biol (Stuttg). 2010 May 1;12(3):437-44
references: 20522179
references: Photochem Photobiol. 1991 Nov;54(5):761-8
references: 1798752
references: Phycologia. 1993;32(5):315-22
references: 11539431
references: Photosynth Res. 1986 Jan;9(1-2):251-9
references: 24442301
references: J Photochem Photobiol B. 1995 Apr;28(1):77-85
references: 7791008
references: Astrobiology. 2008 Feb;8(1):75-86
references: 18240967
references: Microbiol Mol Biol Rev. 2010 Mar;74(1):121-56
references: 20197502
references: Stud Mycol. 2008;61:99-109
references: 19287532
references: J Photochem Photobiol B. 1998 Jul 31;44(3):175-83
references: 9800379
references: Mol Biol Evol. 1987 Jul;4(4):406-25
references: 3447015
references: J Microbiol Methods. 2010 Jan;80(1):1-13
references: 19854226
references: Photochem Photobiol. 2001 Apr;73(4):447-51
references: 11332042
references: Orig Life Evol Biosph. 2009 Dec;39(6):581-98
references: 19629743
references: J Theor Biol. 1973 Apr;39(1):195-200
references: 4741712
references: Icarus. 2000 Aug;146(2):343-59
references: 11543504
references: Syst Appl Microbiol. 2007 Dec;30(8):581-6
references: 17643894
references: Trends Microbiol. 2010 Jul;18(7):308-14
references: 20381355
references: J Photochem Photobiol B. 1995 Oct;30(2-3):171-7
references: 8558369
references: Microbiol Rev. 1994 Dec;58(4):755-805
references: 7854254
references: Biopolymers. 2000;57(3):179-86
references: 10805915
references: Mol Biol Evol. 2007 Aug;24(8):1596-9
references: 17488738
references: Adv Space Res. 2002;30(6):1539-45
references: 12575719
references: Photodermatol Photoimmunol Photomed. 1990 Aug;7(4):159-65
references: 2076371
references: Nucleic Acids Res. 2009 Jan;37(Database issue):D141-5
references: 19004872
references: J Microbiol Methods. 2007 Jul;70(1):1-12
references: 17540467
references: J Photochem Photobiol B. 2008 Feb 27;90(2):79-87
references: 18191576
references: Appl Environ Microbiol. 1998 Dec;64(12):4870-6
references: 9835576
references: Nucleic Acids Res. 1997 Dec 15;25(24):4876-82
references: 9396791
references: J Mol Biol. 1990 Oct 5;215(3):403-10
references: 2231712
references: Appl Environ Microbiol. 2010 Apr;76(7):2115-21
references: 20154120