Variation of Irradiation Effects on Microorganisms in Relation to Physical Changes of Their Environment

Moos, W.S.

doi:10.1128/jb.63.5.688-690.1952

Cited by 25 publications

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“…THE RADIATION sensitivity of vegetative bacteria has been reported to be reduced by a factor of 2-5 times when irradiation takes place in the frozen state as compared with room temperature. Such results have been reported for Escherichia coli (Houtermans, 1954;Bellamy & Lawton, 1955 ;Stapleton & Edington, 1956), Pseudomonas aeruginosa (Moos, 1952), Staphylococcus aureus (Bellamy & Lawton, 1955), and the mixed bacterial population of meat (Coleby, Ingram, Shepherd, Thornley & Wilson, 1961), while similar results were obtained for yeast (Wood & Taylor, 1957;Wood, 1959) when freezing had taken place slowly. The radiosensitivity of spores has been shown to vary to a much smaller extent, or not a t all.…”

Section: Introductionsupporting

confidence: 65%

The Effect of Freezing on the Radiation Sensitivity of Vegetative Bacteria

Matsuyama

Thornley

Ingram

1964

Journal of Applied Bacteriology

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Summary: Five strains of bacteria were irradiated, suspended in heart infusion broth or in phosphate buffer, in aerated or anoxic conditions, at temperatures of 10–13° or ‐79°. Survivors under the different conditions were enumerated by plate counts on heart infusion agar. Exponential survivor‐dose curves were obtained with a Pseudomonas strain and with Escherichia coli B/r when irradiated at room temperature with aeration, whereas an Alcaligenes strain and 2 strains of Streptococcus faecium gave sigmoid curves. The decreased radiosensitivity in the frozen state was measured by comparing the D10 values for exponential curves, or for the exponential portion of sigmoid curves, with that observed for irradiation at room temperature with aeration. This ‘D10 ratio’ svaried between 2°5 and 8·5. For the Alcaligenes strain it was about 4, whether the frozen irradiation took place in the presence or absence of oxygen. With the Pseudomonas irradiated in the frozen state in the absence of oxygen the ‘D10 ratio’ was usually about 1·5 times higher than when oxygen was present. The highest ratio (8·5) was obtained for anoxic irradiation of the Pseudomonas strain. In general, the shapes of survival curves for frozen irradiation differed from those obtained at room temperature. The sigmoid curves for the Alcaligenes strain irradiated under aerobic conditions when frozen showed a marked decrease in extrapolation numbers. E. coli B/r when frozen in heart infusion broth gave a double exponential curve with a shallow slope initially, followed by a steeper slope. The most radiation resistant strain, Strep. faecium R53, gave sigmoid curves with a D10 value of 300 Krads when frozen, and was then of similar resistance to Clostridium botulinum spores.

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Section: Introductionsupporting

confidence: 65%

The Effect of Freezing on the Radiation Sensitivity of Vegetative Bacteria

Matsuyama

Thornley

Ingram

1964

Journal of Applied Bacteriology

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“…Similar protection was reported for Pseudomonas aeruginosa (Moos, 1952), Staphylococcus aureus (Bellamy and Lawton, 1955), and slowly frozen yeasts (Wood and Taylor, 1957). For several vegetative organisms, the sensitivity in the frozen state was found to be comparable to that of the dry organisms (Bellamy and Lawton, 1954).…”

Section: Downloaded Fromsupporting

confidence: 74%

Effect of Temperature of Liquid Nitrogen on Radiation Resistance of Spores of Clostridium botulinum

et al. 1965

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An apparatus consisting of a Dewar flask and a relay system controlling the flow of liquid nitrogen permitted the irradiation of samples in tin cans or Pyrex tubes at temperatures ranging from 0 ± 1.5 C to -194 ± 2 C. An inoculated pack comprising 320 cans of ground beef containing 5 × 10 4 spores of Clostridium botulinum 33A per can (10 cans per radiation dose) was irradiated with Co 60 at 0 and -196 C. Incubation was carried out at 30 C for 6 months. Approximately 0.9 Mrad more radiation was required to inactivate the spores at -196 C than at 0 C. Cans irradiated at -196 C showed partial spoilage at 3.6 Mrad and no spoilage at 3.9 Mrad; the corresponding spoilage-no spoilage doses at 0 C were 2.7 and 3.0, respectively. The majority of positive cans swelled in 2 to 14 days; occasional swelling occurred as late as 20 days. At progressively higher doses, swelling was delayed proportionally to the radiation dose received. The remaining nonswollen cans had no toxin after 6 months of storage, although occasional cans contained very low numbers of viable spores comprising on the average 0.1% of the original spore inoculum. The D 10 values in phosphate buffer were 0.290 Mrad for 0 C and 0.396 Mrad for -196 C; in ground beef, the corresponding D 10 values were 0.463 Mrad and 0.680 Mrad, respectively. These D 10 values indicate that the lethal effect of γ rays decreased at -196 C as compared with 0 C by 13.5% in phosphate buffer, and by 47% in ground beef.

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“…Freezing protects vegetative cells of Escherichia coli against radiation by a factor of two to five times. (Hollaender and Stapleton, 1953;Houtermans, 1954;Bellamy and Lawton, 1955;Stapleton and Edington, 1956 (Moos, 1952), Staphylococcus aureus (Bellamy and Lawton, 1955), and slowly frozen yeasts (Wood and Taylor, 1957). For several vegetative organisms, the sensitivity in the frozen state was found to be comparable to that of the dry organisms (Bellamy and Lawton, 1954).…”

Section: Discussionmentioning

confidence: 97%

Effect of Temperature of Liquid Nitrogen on Radiation Resistance of Spores of Clostridium botulinum1

Grecz

Snyder

Walker

et al. 1965

Applied Microbiology

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GRECZ, NICHOLAS (U.S. Army Natick Laboratories, Natick, Mass.), 0. P. SNYDER, A. A. WALKER, AND A. ANELLIS. Effect of temperature of liquid nitrogen on radiation resistance of spores of Clostridium botulinum. Appl. Microbiol. 13:527-536. 1965.-An apparatus consisting of a Dewar flask and a relay system controlling the flow of liquid nitrogen permitted the irradiation of samples in tin cans or Pyrex tubes at temperatures ranging from 0 i 1.5 C to -194 i 2 C. An inoculated pack comprising 320 cans of ground beef containing 5 X 104 spores of Clostridium botulinum 33A per can (10 cans per radiation dose) was irradiated with Co6O at 0 and -196 C. Incubation was carried out at 30 C for 6 months. Approximately 0.9 Mrad more radiation was required to inactivate the spores at -196 C than at 0 C. Cans irradiated at -196 C showed partial spoilage at 3.6 Mrad and no spoilage at 3.9 Mrad; the corresponding spoilage-no spoilage doses at 0 C were 2.7 and 3.0, respectively. The majority of positive cans swelled in 2 to 14 days; occasional swelling occurred as late as 20 days. At progressively higher doses, swelling was delayed proportionally to the radiation dose received. The remaining nonswollen cans had no toxin after 6 months of storage, although occasional cans contained very low numbers of viable spores comprising on the average 0.1% of the original spore inoculum.The Dio values in phosphate buffer were 0.290 Mrad for 0 C and 0.396 Mrad for -196 C; in ground beef, the corresponding D1o values were 0.463 Mrad and 0.680 Mrad, respectively. These D,o values indicate that the lethal effect of y rays decreased at -196 C as compared with 0 C by 13.5% in phosphate buffer, and by 47% in ground beef.1.5% agar.These two techniques, i.e., the spoilage endpoint, and the direct count technique, were also used for evaluation of spore survival in ground beef. With the end-point technique in glass tubes, the indications of viability of C. botulinum were turbidity, odor, and specific toxin; with canned beef, swelling of cans and specific toxin were the indicators. 527 on July 5, 2020 by guest http://aem.asm.org/ Downloaded from

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Variation of Irradiation Effects on Microorganisms in Relation to Physical Changes of Their Environment

Cited by 25 publications

References 0 publications

The Effect of Freezing on the Radiation Sensitivity of Vegetative Bacteria

The Effect of Freezing on the Radiation Sensitivity of Vegetative Bacteria

Effect of Temperature of Liquid Nitrogen on Radiation Resistance of Spores of Clostridium botulinum

Effect of Temperature of Liquid Nitrogen on Radiation Resistance of Spores of Clostridium botulinum1

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