The influence of nutrition and temperature on the growth of colonies of Escherichia coli K12.

Growth of Escherichia coli was faster in liquid cultures than on the same medium solidified with agar. Colony profiles indicated a common basic structure with a size variation due to nutritional conditions. Radial growth rates were linear and height also increased approximately linearly, especially in the early part of the growth period. The ratio of rate of height increase to diameter increase depended on nutrition. Conditions favouring rapid growth led to faster radical growth relative to height increase. A rise in incubation temperature led to increases in height and in diameter: however, diameter increased relatively more than height. These results are discussed in terms of the structure of the colony.