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Influence of Space Flight on the Genetics of Streptomyces lividans 66 – pIJ702. 

T. L. Goins¹, V.G. Martinson¹, V.Yu. Tabakov², T. A. Voeikova², and B. H. Pyle¹.  ¹Department of Microbiology, Montana State University, Bozeman, Montana, and ²GosNIIGenetika, 1 Dorozhnyi proezd, Moscow 117545, Russia.

   Gram-positive bacteria belonging to the genus Streptomyces are characterized by a high level of genetic instability in response to external factors. Streptomyces lividans is a typical representative species with a complex life cycle including vegetative mycelia and sexual spores.  The strain selected to study specific spaceflight factors (SSF) was S. lividans 66 harboring the multi-copy plasmid pIJ702.  The possible effects of radiation and microgravity on genetic stability were assessed using the plasmid marker genes for melanin production and thiostrepton antibiotic resistance.  Cultures of S. lividans 66 [pIJ702] were flown on Foton-M2 (May 31 – June 16, 2005) with on-board radiation and temperature monitors.  An asynchronous ground control (AGC) mimicked the growth temperature of the flight cultures, while an additional laboratory control (LC) grew the cultures under optimal maturation temperature (26°C to 28°C).  Unfortunately, the temperature aboard Foton-M2 was 15°C to 20°C during flight and did not permit maturation of the culture.  Post-flight, the flight and AGC cultures were maintained at 2°C to 10°C until being permitted to differentiate at 28°C for five days to facilitate sporulation.  Clones recovered under thiostrepton selection were also melanin negative indicating a loss of pIJ702.  Additionally, non-melanized clones recovered on non-selective media proved to be thiostrepton sensitive upon transfer to media containing the antibiotic.  The rate of pIJ702 loss was significantly higher in the flight and asynchronous ground control clones than in the laboratory control clones, indicating a temperature effect.  Neither microgravity nor radiation effects were detected as there was no significant difference between flight and AGC clones.  However, lack of differentiation may have obscured the effects of radiation exposure (200-300 mRad) or microgravity on genetic instability.     

(Supported by the Institute for Biomedical Problems, Moscow, Russia, and NASA: NCC2-1143.)