Studies on the Life and Death of Bacteria

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Abstract
In aging broth cultures of Sarcina lutea and Serratia mar-cescens, the numbers of cultivable bacteria remaining after 2 years of incubation were still remarkably large. Similar findings were obtained with a number of other bacteria after one year of incubation. When the counts were plotted logarithmically, the resulting curve, after the initial drop following the maximum stationary phase, tended to level off and maintain an almost imperceptible decline. The term "senescent phase" is suggested for this period of the curve. The species retained their microscopic and physiologic characteristics. The aging cells possessed a marked resistance to adverse environmental conditions. Varying degrees of growth occurred with 21 strains of organisms cultured on media in which the only source of nutriment was a large quantity of washed and autoclaved bacterial cells. Similar results were obtained with S. marcescens using a liquid medium consisting of a suspension of killed cells of S. marcescens in saline.

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