Dynamics of rate limiting enzymes involved in the sequential substrate uptake by Pseudomonas putida CSV86: Modeling and experimental validation

Cybernetic model assumes that a microorganism is an optimal strategist, sets goals, sub-goals and sub-sub-goals, monitors its performance against these goals and then takes remedial action. The soil bacterium Pseudomonas putida CSV86 is known for its ability to preferentially utilize aromatic compounds over glucose. We had set up a structured kinetic model where sub-goals are based on the environmental conditions. Upon exhaustion of the preferred hydrocarbon substrate, the organism sets a sub-goal of utilization of the less preferred glucose substrate and in-turn induces the relevant rate limiting enzymes. The model parameters were estimated from batch data and validated in the dynamic phase of a chemostat, which was subjected to pulse input of the preferred substrate. We find that the organism not only grows faster on the preferred hydrocarbon substrate but also adapts faster. Specifically, the rate of synthesis of the rate limiting enzyme for benzyl alcohol utilization is approximately seven times greater than that for glucose. The recovery time from the pulse of benzyl alcohol reduced dramatically with the increasing dilution rate. This is partially attributed to a higher enzyme synthesis rate at higher dilution rates in addition to the obvious effect of quicker benzyl alcohol washout. (C) 2010 Elsevier Ltd. All rights reserved