Shelf life and sensory characteristics of baby spinach subjected to electron beam irradiation.

The use of ionizing radiation for the control of foodborne pathogens and extending the shelf life of fresh iceberg lettuce and fresh spinach has recently been approved by the U.S. Food and Drug Administration. The efficacy of electron beam irradiation for controlling foodborne pathogens has been reported. For this experiment, the effectiveness of electron beam irradiation on the microbiological and sensory characteristics of fresh spinach was studied. Total aerobic plate counts were reduced by 2.6 and 3.2 log CFU/g at 0.7 and 1.4 kGy, respectively. Lactic acid bacteria were reduced at both doses of e-beam but grew slowly over the 35 d of the experiment. Yeasts and molds were not reduced in samples exposed to 0.7 kGy whereas 1.4 kGy significantly reduced microbial counts. Gas compositions (O(2) and CO(2)) were significantly different than controls. Oxygen levels inside the spinach sample bags decreased over time; however, O(2) levels did not drop below 1% that can induce anaerobic fermentation. CO(2) levels for all treatments increased through day 4; yet 7 d after irradiation, CO(2) level differences were not significant in both control and irradiated samples. Irradiation dose did not affect the basic tastes, aromatics, or mouth feels of fresh spinach, however; hardness attributes decreased as irradiated dose increased and slimy attributes of fresh spinach were higher in control samples compared to irradiated samples.

Phylogenetic characterization of a novel radiation-resistant bacterium from irradiated pork: description of Hymenobacter actinosclerus sp. nov.

A phylogenetic analysis was performed on a red-pigmented, radiation-resistant, Gram-negative, rod-shaped organism originating from irradiated pork. Comparative 16S rRNA gene sequencing showed the bacterium was a member of the Cytophaga-Flavobacterium-Bacteroides line of descent and represents a new subline within the genus Hymenobacter. A new species, Hymenobacter actinosclerus, is described for this novel radiation-resistant bacterium. The type strain of Hymenobacter actinosclerus is CCUG 39621T.

Radiotoxicity of plutonium in NTA-degrading Chelatobacter heintzii cell suspensions.

The radiotoxicity of plutonium in NTA-degrading Chelatobacter heintzii cell suspensions was investigated as part of a more general study to establish the key interactions between actinide-organic complexes and microorganisms in the subsurface. The radiation tolerance of C. heintzii, based on 60Co gamma irradiation experiments, was 165 +/- 30 Gy. No bacteria survived irradiation doses greater than 500 Gy. In the presence of plutonium, where alpha particle decay was the primary source of ionizing radiation, the observed toxicity was predominantly radiolytic rather than chemical. This was evident by the greater effect of activity, rather than concentration, on the toxicity noted. Bioassociation of plutonium with C. heintzii was postulated to be an important and necessary step in the observed loss of cell viability since this was the best way to account for the observed death rate. The radiotoxicity of plutonium towards bacteria is a potentially important consideration in the bioremediation of sites contaminated with radionuclide-organic mixtures and the bioprocessing of nuclear waste.

[The effect of long-acting radiation on the diversity of heterotrophic bacteria in the soils of a 10-kilometer area around the Chernobyl Atomic Electric Power Station]. / Vliianie radiatsii dlitel'nogo deistviia na raznoobrazie geterotrofnykh bakterii v pochvakh 10-kilometrovoi zony Chernobyl'skoi atomnoi élektrostantsii.

The catastrophe at Chernobyl Atomic Power Station (ChAPS) of 1986 has created a natural model for studying the after-effects of prolonged action of radiation on the biota. Our work is aimed to estimate the variability of heterotrophic bacteria in the soil of 10-km zone of ChAPS which have formed as affected by prolonged action of radiation, as well as to create the corresponding collection of bacteria. Microbiological analysis of soils was carried out in 1993-1994 (in spring, summer, autumn), allowing for bacteria destroying different organic substance (in soil). It is shown that in the surface layer of soils (at the depth of 0-2 cm) the total number of cells of heterotrophic bacteria as well as the number of found species of bacteria is considerably less than in the control samples. Atypical distribution of bacteria in the soil profile was established. Indices of the species diversity of bacteria in these soils permit one to consider that microbe content of soil of the 10-km zone of the ChAPS has become considerably less after the disaster at the ChAPS in 1986 and has not recovered by 1993. A collection of various physiological groups of bacteria including representatives of Methylobacterium genus has been created. They have been isolated from the soils of 10-km zone of the ChAPS for following genetic investigations.

[Sterilization by ionizing radiations (author's transl)]. / La stérilisation par les rayonnements ionisants

The first part summarizes the general characteristics of ionizing radiations and their activity on microorganisms: lethal and mutagenic effects, sensitivity conditions. Different microbial species have different sensitivities: gram negative bacteria are more sensitive (D10 approximately 5-10 Krads), bacterial spores and viruses are more resistant (D10 approximately 1 Megarads). The second part considers the main applications of radiosterilization: some are at present in full development (medical and surgical disposable equipment); others are still at the experimental stage. Practical aspects, determination of sterilizing doses and control of radiosterilization are also described.