Growth and survival of Pseudomonas putida strains degrading naphthalene insoil model systems with different moisture levels

The effect of different moisture levels (from 20 to 70%) on the growth and survival of Pseudomonas putida strains G7 and BS3701 degrading naphthalene was studied in soil model systems. P. putida G7 contains plasmid NAH7 and P . putida BS3701 harbours plasmids pBS1141 and pBS1142. A mathematical model is proposed to describe the observed dynamics of the number of viable bact erial cells. Naphthalene and soil organic matter were considered as substra tes available to bacteria. Data fitting allowed the estimation of model par ameters characterizing microbial growth rate, utilization rate of substrate s, specific maintenance rate and yield coefficient. Both the maximum bacter ial concentration and the highest yield coefficient were observed at a soil moisture level of 40%. This optimal moisture level is close to but less th an the water capacity (48%) of the soil used. (C) 1999 Elsevier Science Ltd . All rights reserved.