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Appl Environ Microbiol. 1963 September; 11(5): 413-417

Inactivation of the Radiation-Resistant Spoilage Bacterium Micrococcus radiodurans

II. Radiation Inactivation Rates as Influenced by Menstruum Temperature, Preirradiation Heat Treatment, and Certain Reducing Agents¹, ^,2, ^,3

Department of Microbiology, Oregon State University, Corvallis, Oregon

ABSTRACT

The R₁ strain of Micrococcus radiodurans, previously determined to be more resistant than three other strains exposed to gamma radiation, was studied further to determine the influence of certain environmental factors on resistance to radiation inactivation. The frozen state offered insignificant protection to the organisms irradiated in raw puréed beef. Resistance was reduced by higher menstruum temperatures (40 and 50 C) during irradiation. Preirradiation heat treatment was found to lower resistance to subsequent irradiation. When the cells were irradiated in buffer at pH 5, 7, or 9, no differences in resistance were noted. Cell suspensions in buffer were protected to some extent by cysteine but not by thioglycolate. Ascorbate enhanced radiation inactivation.

⁴ Present address: Department of Microbiology, University of Kansas School of Medicine, Kansas City.

¹ This paper reports research undertaken in cooperation with the Quartermaster Food and Container Institute for the Armed Forces, Q. M. Research and Engineering Command, U.S. Army, and has been assigned no. 2239 in a series of papers approved for publication. The views or conclusions contained in this report are those of the authors. They are not to be construed as necessarily reflecting the views or endorsements of the Department of Defense.

² Technical Paper no. 1598, Oregon Agricultural Experiment Station; contribution of the Department of Microbiology.

³ Presented at the 62nd Annual Meeting of the American Society for Microbiology, Kansas City, Mo., 8 May 1962.