Relative Resistances of Microorganisms to Cathode Rays

Abstract

The method used in evaluating the respiratory protection provided by representative types of contagion masks against an aerosol of Bacillus subtilis var. niger spores has been described. It can be concluded that the contagion masks evaluated offer poor respiratory protection against airborne microorganisms in the particle size range of 1.0 to 5.0 ,u in diameter. Commercially available dust respirators and related masks are approximately 2.5 to 5 times more efficient than contagion masks. An even higher degree of protection can be obtained by the use of full-face masks.

The Influence of Environmental Factors on the Microbicidal Effect of Ionising Radiations

“…Over a wide range the fractional survival curve for a given organism is independent of the initial concentration of cells under controlled gaa conditions. Koh, Morehouse & Chandler (1956) reported a protective effect as the concentration of their suspension of E. wli increased above a certain level, and a similar effect was reported for Pseudomonas geniculata (Doty et al 1956). Gunter & Kohn (1956b) showed this to be due to removal of dissolved oxygen by the respiration of the dense suspension of vegetative bacteria.…”

“…Houtermans (1953), using synchronized cultures of E. wli, showed that the sensitivity to a-particlea and ultraviolet radiation was greater just after division than in the preceding stages. Spores have been reported to be more resistant than their corresponding vegetative forms (Koh, Morehouse & Chandler, 1956), but Laser (1956) found fresh B. subtilis spores to have about the same radiosensitivity as the vegetative forms. However, Laser's technique for measuring survival (manometric determinations of oxygen uptake) was sufficiently different from those generally in use for the results not to be strictly comparable.…”

Incidence and Characteristics of Beta Radiation Survivors (Escherichia coli)

“…Lea (1936) found that when Bacillus mesentericus spores, Escherichia coli and Staphylococcus aureus were irradiated by alpha and beta particles from polonium and radium respectively, the numbers surviving diminished exponentially as a function of the dose. More recently, bacteria, bacterial spores, yeasts, fungi and viruses have been exposed to high voltage electrons and in all cases similar exponential survival patterns were demonstrated (Dunn et al, 1948;Katznelson et al, 1952;Edwards et al, 1954;Bellamy and Lawton, 1954;Koh et al, 1956;Bridges et al, 1956;Pepper et al, 1956;and Fluke and Pollard, 1955).…”

Inactivation of the Radiation-Resistant Spoilage Bacterium Micrococcus radiodurans

“…But Wolin, Evans, and Niven (1957) reported a concentration effect with Pseudomonas geniculata. Koh, Morehouse, and Chandler (1956) reported apparent protective effects as the concentration of Escherichia coli increased above a certain level. High concentrations of bacteria may, by lowering the oxygen content of the menstruum, seem thereby to protect the organisms.…”