A continuous culture study of an obligately psychrophilic Pseudomonas species.

Abstract

The optimum temperatures for growth and respiration of an obligately psychrophilic Pseudomonas spec. were 14°C and 23°C, respectively. The maximum temperature for growth was between 19 and 20°C. When cells were grown in a chemostat with lactate as the growth-limiting substrate at a specific growth rate of 0.05 hr-1 over a temperature range of 5–19°C, it was found that RNA concentration was lowest at 14°C. At lower temperatures the cells compensated the decrease of reaction rates by increasing the concentration of RNA and of respiratory enzymes. A temperature raise above 14°C also increased cellular RNA, which probably counteracted an impairment of protein synthesis. Above 18°C the RNA increase ceased, resulting in a rapid decrease of protein synthesis, until between 19 and 20°C growth ceased entirely. Cells grown at 14°C showed a linear increase of RNA content and \(Q_{0_2 }\)values with growth rate, when this was varied from 0.025 to the maximum value of 0.2 hr-1.