Growth of Bacteria in the Heat-Killed Cell Suspensions of the Same Bacteria

Abstract

The course of growth of several bacteria in the heat-killed cell suspension of the respective strains was traced by counting the viable cell numbers. 1) The mean generation time of Escherichia coli was dependent on the concentration of the heat-killed cells. The maximum growth rate, mean generation time of 35 min, was attained at the concentration of 25x109 or more heat-killed cells per ml. The mean generation time was comparable to that in the casamino acids-salt mixture medium. Final cell number attained was about 1% of that of the heat-killed cells initially supplied. The ratios of the number of viable cells to the heat-killed cells were fairly constant over a wide range of the concentration of the heat-killed cells, but they were smaller in lower concentration. The mean generation time and final yield increased in the medium supplemented with either glucose or ammonium chloride, and particularly, the effect of ammonium chloride on the reduction of the mean generation time was prominent. 2) Similar experiments were carried out with 9 other species of bacteria using suspensions of 2 to 3x109 heat-killed cells per ml. Some bacteria grew in their own heat-killed cell suspensions fairly rapidly after a short lag period. By contrast, Achromobacter liquefaciens failed to grow in its heat-killed cell suspension. The final yields of viable cells per unit number of heat-killed cells supplied were different from species to species. Among them, Arthrobacter simplex and Pseudomonas aeruginosa were the highest, and one new cell was produced at the expense of 13 to 14 heat-killed cells, while the others needed as many as 300 to 2, 000 heat-killed cells. 3) The effect of addition of glucose, ammonium chloride, sodium glutamate or inorganic salts on the growth and the final yield of several bacteria grown in their heat-killed cell suspension was studied. Most bacteria responded to ammonium chloride and sodium glutamate, and their final yield more or less increased, whereas they did not show any appreciable response to glucose. Growth of Serratia marcescens was completely suppressed by glucose. Phosphate was not effective in increasing the final yield of all the bacteria tested. The growth of some bacteria was much increased by the addition of salt mixture other than phosphate. © 1968, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.