Recovery of x‐irradiated bacteria at suboptimal incubation temperatures

Abstract

The observation of recovery of living cells from the effect of ionizing radiations has been reported repeatedly. The literature concerning this effect has been reviewed by Lea ('47) and more recently by Gray ('52) and Allen et al. ('51). Revera1 techniques have been employed to demonstrate recovery in living organisms, eg., comparison of the efficiency of single and fractionated doses of a radiation or comparison of the efficiency of a radiation applied at high and low intensities. Tlie use of these techniques has yielded information coiicerning the recovery which occurs during the course of radiation exposure. A review of the literature (Lea, '47) indicates that bacteria irradiated in aqueous suspensions do not recover during the exposure to ionizing radiations. Some types of cells a r e able to recover from the effects of ionizing radiations if maintained in the cold or in a starved condition after irradiation (Strangeways and Fell, '27 ; Spear and Gliicksmann, '39; Cook, '39; Allen et al., '51). I n some of the cases reported, however, apparent recovery was in fact merely a postponement of the radiation effect, which was shown to take its normal course when active metabolism and growth were resumed. Latarjet ('43) showed that holding bacterial cells on nutrient agar a t refrigerator temperatures

'Restoration' of Escherichia coli strain B After Irradiation: its Dependence on Suboptimal Growth Conditions

“…( d ) The action of the factors in the medium was much more pronounced with logarithmic than with stationary-stage bacteria; the latter, as is well known, take longer to go into division after re-inoculation. Nevertheless, not all conditions which slowed growth could protect Escherichia coli strain B organisms after irradiation against factors in the medium; incubation of this strain at suboptimal temperatures did not promote 'recovery ', in contrast to the observations made by Stapleton, Billen & Hollaender (1953) on other strains of E . coli.…”

“…The majority of these have shown evidence of 'restoration' or ' recovery' in conditions which would normally be regarded as suboptimal for the growth of the organisms (Latarjet, 1943;Roberts gS Aldous, 1949;Stein & Meutzner, 1950;Anderson, 1951;Stapleton et al 1953;Buzzell, 1956;Barner & Cohen, 1956), or else in conditions in which a preliminary incubation period was allowed in a medium which permitted some metabolism to occur, but did not provide all the nutrients required for division (Wainwright & Nevill, cannot be interpreted directly as indicating that the plating medium supplied a biochemical need induced by irradiation. Bacteria which had been grown in nutrient broth showed greater survival when plated on nutrient than on minimal agar, but the extent of the survival of these bacteria was no greater than that of bacteria grown in minimal liquid medium, before irradiation, and plated afterwards on minimal agar.…”

The Relationship between Growth and Survival after Irradiation of Escherichia coli Strain B and two Resistant Mutants

“…Stapleton, Billen & Hollaender (1955) reported that strain B/r survived X-rays to the greatest extent if the cells were held at 1 8 ' for several hours after X-irradiation. We have confirmed this result, but have found that after U.V.…”

Combined Ultrasonic and Gamma-irradiation ofEColi B

“…(i) It has been established that post-gamma-irradiation storage in nutrient media before plating at temperatures in the region 10°to 20°C which would result from the sonication, would lead to an increase in survival owing to repair (Stapleton et al 1953) . Although the temperature excusion for the pre-y case would place the sample temperature in this region for only a limited period under conditions of a very dilute nutrient medium, it may reasonably be concluded that any effect on SF22 should be in the direction of higher survival and not lower as observed .…”