The Effects of Sublethal Doses of Monochromatic Ultraviolet Radiation on the Growth Properties of Bacteria

Abstract

Bacteria suspended in physiol. salt radiation were exposed to measured quantities of monochromatic u.-v. radiation. Two effects of sub-lethal doses of u.-v. radiation were observed on surviving organisms: (a) an apparent initial increase in number of colony-forming organisms, and (b) an extension of the resting (lag) phase. Methods and procedures are described which make possible the recognition of the sublethal effects. The effects are illustrated by typical exps. The influence of a number of factors in regard to the appearance of the sublethal effects is descr. Possible explanations of the effects are discussed.