Growth and comparative physiology ofKlebsiella oxytoca attached to granular activated carbon particles and in liquid media

Abstract

Experiments were performed to evaluate the comparative growth and physiology ofKlebsiella oxytoca grown attached to granular activated carbon particles (GAC) and in liquid medium. Laboratory studies showed that when this organism attached to GAC, the growth rate was enhanced more than 10 times in the presence of glutamate, a substrate that adsorbed to the surface. No differences were observed if the substrate was glucose, which did not adsorb to GAC. Cellular [³H]thymidine uptake was used to estimate DNA biosynthesis. Attached bacteria grown in a minimal nutrient medium containing 20.0 mg/liter glutamate took up 5 times more [³H]thymidine than cells grown in suspension. [³H]uridine was used as a measure of RNA turnover. Attached cells were shown to assimilate 11 times more [³H]uridine than cells in liquid media. Cell size measurements were performed by differential filtration. Cells grown in a minimal medium with 20.0 mg/liter glutamate decreased in size over time, with 62% of the total number passing through a 1.0μm filter after 9 days incubation. In the same period, 39% of a cell population that was grown on GAC passed through a 1.0μm filter. These studies indicate that GAC provides an interfacial environment for the enhanced growth ofK. oxytoca when glutamate is the substrate.