Dissolved hydrocarbon metabolism: The concentration‐dependent kinetics of toluene oxidation in some North American estuaries 1

The metabolism of toluene by natural populations of marine bacteria, stored to enhance their activity, gave hyperbolic kinetics with saturation at only K t = 0.6 to 3.4 µ g liter −1 . Similarly K t in fresh seawater was 0.26 µ g toluene liter −1 . Freshly collected populations could be moderately active toward toluene, affinity a 2 A = 1.1−37.5 liters g‐cells −1 h −1 . These moderate affinities taken together with the small K t values give an explanation for the failure of most marine bacteria to grow at the expense of a single hydrocarbon. In two experiments there was a significant first‐order region in toluene in the 10–50 µ g liter −1 range. When cultures of Pseudomonas sp. strain T2 were cast in suspended agar blocks to impede diffusion, toluene oxidation still followed hyperbolic kinetics although CO 2 production and organic product formation were characterized by larger Michaelis constants. A large widespread population of bacteria with inducible capacity to metabolize hydrocarbons is indicated. Observed turnover times for toluene were 0.2–40 years with growth rates of 10 −6 h −1 from toluene at 1 µ g liter −1 .