PRINCIPAL INVESTIGATOR (S ): R. H. T. Mattoni, E. C. Keller, William T. 



Ebersold, F. A. Eiserling, and W. R. Romig 



EXPERIMENT TITLE/NUMBER : Induction of Lysogenic Bacteria in the Space 



Environment, P-1135 



PROGRAM/MISSION : Biosatellite II 



CLASSIFICATION : Microorganism - ( Salmonella typhimurium . Escherichia coli ) 



DISCIPLINE(S) : Radiobiology , Genetics, Cell biology 



OBJECTIVES : To test the hypotheses that weightlessness both with and without 

 gamma irradiation would not affect bacterial cell growth or induction of 

 bacterial prophage P-22. 



PROTOCOL : The bacteria were used to study the induction of lysogeny, a 

 biological process extremely sensitive to a variety of environmental factors 

 such as vibration and radiation. Free phage and bacterial density were also 

 studied. Nine sets of cultures, each consisting of replicate chambers of 1.4 

 +_ 0.3-ml capacity, were prepared to test the effects of ( 1 ) spaceflight, 

 (2) three chronic gamma-irriadiation dose levels and (3) temperature. Each 

 chamber was inoculated with aliquots of a suspension of bacteria adjusted to 

 give mean viable density of about 100 cells/ml. 



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 EQUIPMENT : Four experiment packages, Sr source. 



RESULTS : The data on bacterial growth led to rejection of the hypotheses: 

 space flight produced both increased density of Salmonella typhimurium when 

 grown in liquid medium and interaction to give greater resistance to gamma 

 irradiation at levels between 265 and 1648 R total dose (17 and 103 R per 

 average cell generation). Tests of other variables eliminated all but 

 weightlessness in accounting for the difference. On the basis of the T tests 

 there was no difference in the free phage per bacterium produced under 

 conditions of control and those of flight. The induced bacteriophage per 

 viable bacterium showed significant differences between flight and control at 

 two radiation levels (265 and 645 R). The flight set had consistently lower 

 yields at all levels of radiation. The Escherichia coli experiment was 

 incomplete since the growth phase had not reached maximum because of early 

 call-down of Biosatellite II. 



CONCLUSIONS : The growth rate of Salmonella typhimurium appeared to be more 

 rapid during spaceflight than in the Earth controls. The free phage induction 

 was consistently lower in the flight population versus the Earth controls. 

 The greater bacterial densities (maximum population) are believed to be a 

 function of random cell distribution in the liquid medium under reduced 

 gravity conditions. 



PUBLICATIONS : 381, 382 



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