Combined Effects of Ultrahigh Vacuum and Temperature on the Viability of Some Spores and Soil Organisms

Considerably fewer spores ofBacillus stearothermophilus, B. megaterium , andClostridium sporogenes were recovered than were spores ofB. subtilis var.niger andAspergillus niger after 4 to 5 days at 53 and 60 C in ultrahigh vacuum. There were no significant differences in the recoveries of these five organisms at 25 C and atmospheric pressure, and after exposure to 25 and -190 C in vacuum. At 60 C, a far greater decrease in viability was demonstrated forB. stearothermophilus, B. megaterium , andC. sporogenes in ultrahigh vacuum than at atmospheric pressure. ViableB. subtilis var.niger spores were not detected in an initial 107 spores after retention at 90 C and ultrahigh vacuum, and 104 spores were viable after 5 days at 90 C and atmospheric pressure from an initial 106 spores. Molds and actinomycetes in soil were particularly resistant up to 69 C in vacuum. Actinomycetes were the only soil organisms recovered so far at 120 C.