Incorporation of 32 P and Growth of Pseudomonad UP-2 on n -Tetracosane

Abstract

Cultures of the marine pseudomonad UP-2 growing on n -tetracosane contained both free cells and cells bound to the solid hydrocarbon. After separation by filtration through a Whatman no. 1 filter, the numbers of free and bound cells were estimated from the amount of 32 P incorporated into each fraction and the determined value of 32 P incorporation per viable cell in the filtrate (free cells). During the early exponential growth phase, over 80% of the cells were bound to large pieces of n -tetracosane; as the culture approached the stationary phase, the number of bound cells remained constant, whereas free cells continued to accumulate. Pulse-labeling experiments indicated that cells grew both on the surface of the solid and in the aqueous medium. During the growth cycle, a portion of the n -tetracosane which was initially nonfilterable was recovered in the filtrate in a form which was largely cell associated. This cell-associated n -tetracosane was preferentially utilized and could completely account for the observed growth of free cells.