An orange-brown, catalase-positive coccus was isolated from irradiated haddock. The new coccus was found to consist of rough and smooth strains as well as strains possessing appreciably less pigment. The smooth strain (248) was more radioresistant to gamma radiation than the rough strain, and at higher radiation doses was of comparable resistance to Mficrococcus radiodurans. The less-pigmented strain was as radioresistant as its parent strain (248). Although morphologically similar to other, but less-resistant, micrococci, the coccus differed by growing slowly on solid media, and was unable to grow in 7 % salt. It was distinguished from 311. radiodurans by being smaller in size and in being capable of reducing nitrate to nitrite and hydrolyzing gelatin.

No abstract

Viability studies were conducted on microbial spores subjected to ultrahigh vacuum (UHV) in the 10-9 to 10-10 torr range. After 5 to 7 days in vacuum, they were exposed to ultraviolet (UV) or to y radiation either while still under vacuum or in the presence of dried air. Among the four test organisms subjected to UHV and ultraviolet radiation, Aspergillus niger was the most resistant; Bacillus megaterium, B. subtilis var. niger, and B. stearothermophilus were about equally less resistant. All four spores were more sensitive to ultraviolet radiation when UHVdried than when desiccant-dried. Of the four test organisms subjected to UHV and y radiation, B. megaterium proved to be the most resistant; A. niger was the least resistant; and the remaining two organisms were of intermediate resistivity. All four organisms were less radiation resistant when UHV-dried than when irradiated in their normally hydrated state, and all showed an increased radiosensitivity after vacuum drying when oxygen was present. In addition, spores of B. subtilis var. niger and A. niger were less radiosensitive when UHV-dried and irradiated in vacuum than when "wet" and irradiated in air, whereas the reverse relationship was observed for the remaining two organisms. Based on the fact that microbial contaminants can be readily shielded from UV light by soils, metal particles, etc., and considering that the levels of ionizing radiations reported to be present in interstellar space are generally lower than those used in these experiments, the decrease in radioresistivity imparted by UHV drying is not of a sufficient magnitude to sterilize dependably portions of a spacecraft while on a mission.

effects of ultrahigh vacuum and temperature on the viability of some spores and soil organisms. Appl. Microbiol. 11:202-210. 1963.-Considerably fewer spores of Bacillus stearothermophilus, B. megaterium, and Clostridium sporogenes were recovered than were spores of B. subtilis var. niger and Aspergillus 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 for B. stearothermophilus, B. megatei-ium, and C. sporogenes in ultrahigh vacuum than at atmospheric pressure. Viable B. 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 atmosplheric 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.

SUMMARY Spores of Bacillus subtilis var. niger and B. stearothermophilus irradiated in nitrogen were killed in greater numbers in the presence of vitamin KC, 4.amino‐1‐naphthol, or 2‐amino‐1‐naphthol than when irradiated without chemical. When irradiation was performed in air, the chemicals were without effect, or even protective. Spores of both organisms were particularly sensitive when irradiated in nitrogen with 4‐amino‐1‐naphthol. Irradiation of Micrococcus radiodurans in anoxia with these naphthol derivatives gave losses in cell recovery that resulted in much lower populations than could he attributed to chemical toxicity per se. These chemicals were found to be toxic to a yeast that had been isolated from frozen orange juice when the preparations were in buffer of pH 7.0 and 4.0. When the yeast was suspended in orange juice, on the other hand, the chemicals were neither toxic nor radiosensitizers. Milk was also found to interfere with the bactericidal and radiolethal activities of these chemicals. Sulfhydryl compounds were shown to decrease radiolethal action.

No abstract

Viability studies were conducted on microbial spores subjected to ultrahigh vacuum (UHV) in the 10 -9 to 10 -10 torr range. After 5 to 7 days in vacuum, they were exposed to ultraviolet (UV) or to γ radiation either while still under vacuum or in the presence of dried air. Among the four test organisms subjected to UHV and ultraviolet radiation, Aspergillus niger was the most resistant; Bacillus megaterium, B. subtilis var. niger , and B. stearothermophilus were about equally less resistant. All four spores were more sensitive to ultraviolet radiation when UHV-dried than when desiccant-dried. Of the four test organisms subjected to UHV and γ radiation, B. megaterium proved to be the most resistant; A. niger was the least resistant; and the remaining two organisms were of intermediate resistivity. All four organisms were less radiation resistant when UHV-dried than when irradiated in their normally hydrated state, and all showed an increased radiosensitivity after vacuum drying when oxygen was present. In addition, spores of B. subtilis var. niger and A. niger were less radiosensitive when UHV-dried and irradiated in vacuum than when “wet” and irradiated in air, whereas the reverse relationship was observed for the remaining two organisms. Based on the fact that microbial contaminants can be readily shielded from UV light by soils, metal particles, etc., and considering that the levels of ionizing radiations reported to be present in interstellar space are generally lower than those used in these experiments, the decrease in radioresistivity imparted by UHV drying is not of a sufficient magnitude to sterilize dependably portions of a spacecraft while on a mission.

SUMMARY The radiosensitizing activity of a series of naphthalene derivatives against Streptococcus faecalis and Escherichia coli was examined to determine the essential molecular substituents and configurations required for effective sensitization when the compounds and organisms were irradiated with Co60 gamma rays. In general, compounds with hydroxyl or amino groups in the ortho and para positions, such as 1‐amino‐2‐naphthol and 4‐amino‐1‐naphthol, were particularly effective sensitizers for S. faecalis irradiated in air or in anoxia. E. coli was particularly sensitive to 4‐amino‐1‐naphthol and 5‐amino‐1‐naphthol when irradiated in anoxia, and less sensitive in air. Both organisms displayed marked sensitivity when irradiated with iodoacetic acid in air and in anoxia. It was determined that the bacteria and chemicals must be irradiated together for maximal radiosensitization to take place, for it was possible to almost eliminate radiosensitization by washing the cell‐chemical suspension prior to irradiation.