Growth of Pseudomonas aeruginosa in tap water in relation to utilization of substrates at concentrations of a few micrograms per liter

Abstract

Five P. aeruginosa strains were tested for the utilization of 47 low-molecular-weight compounds as their sole sources of carbon and energy for growth at a concentration of 2.5 g/liter. Of these compounds, 31 to 35 were consumed. Growth experiments in tap water at 15°C were carried out with one particular strain (P1525) isolated from drinking water. This strain was tested for the utilization of 30 compounds supplied at a concentration of 25 μg of C per liter. The growth rate (number of generations per hour) of strain P1525 in this tap water was approximately 0.005 h-1, and with 10 compounds it was larger than 0.03 h-1. An average yield of 6.2 X 109 colony-forming units per mg of C was obtained from the maximum colony counts (colony-forming units per milliliter). The average yield and maximum colony count of strain P1525 grown in tap water supplied with a mixture of 45 compounds, each at a concentration of 1 μg of C per liter, enabled us to calculate that 28 compounds were utilized. Growth rates of two P. aeruginosa strains (including P1525) in various types of water at 15°C were half of those of a fluorescent pseudomonad. The concentration of assimilable organic carbon calculated from maximum colony counts and average yield values amounted to 0.1 to 0.7% of the total organic carbon concentrations in five types of tap water. The assimilable organic carbon percentages were about 10 times larger in river water and in water after ozonation.