The lethal effects of irradiation on Bacillus subtilis HA 101 (59) strains at 

 peak wavelengths of 254 and 280 nm were greater for dried spores than those in 

 water suspensions. The F strain was more sensitive at both wavelengths. 

 Greater loss in viability was found when spores of Bacillus subtilis 168 were 

 exposed to space vacuum and solar UV irradiation at 254 nm. No change in 

 survival with vacuum alone was noted. 



Escherichia coli T-7 bacteriophage was resistant to space vacuum. There was 

 some sensitivity to solar UV irradiation at 254 nm. The dose response curve 

 had the same shape as the ground controls. 



Trichophyton terrestre and Saccharomvces cerivisiae showed an insignificant 

 decrease in viability to solar UV irradiation. Chaetomium globosum and 

 Rhodotorula rubra demonstrated no significant change in survival rate. 



The results of the dosimetry experiments indicated that the optical filter 

 components of the MEED performed in a manner which allowed critical evaluation 

 of exposed biological test systems. 



CONCLUSIONS : No statistically valid differences could be detected in the 

 survival of flight samples when compared to corresponding ground controls. In 

 general, these evaluations were based on multiple observations of from 10 to 

 30 replicates of up to one million cells each. While the results of this 

 experiment conflict with those of certain other space flight investigations, 

 it must be observed that the conditions of a particular space flight cannot be 

 exactly duplicated, and therefore results from different flights are not 

 directly comparable. 



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