Reaction Engineering Aspects of Conjugation in Biodegradation Processes

Abstract

Conjugation between two Pseudomonas putida species has been studied. Special emphasis has been given to the design of tools for better defined and reproducible experimental conditions. This is an essential prerequisite for any kinetic analysis of the phenomenon. The experimental approach suggested in the paper is a three-stage continuous fermentation, where donor and recipient strains can be cultivated at predefined steady-state growth rates, and conjugation takes place at steady-state conditions in the third stage. For the first time a remarkable influence of agitative speed on conjugation has been experimentally observed.

Low-Frequency Horizontal Transfer of an Element Containing the Chlorocatechol Degradation Genes from Pseudomonas sp. Strain B13 to Pseudomonas putida F1 and to Indigenous Bacteria in Laboratory-Scale Activated-Sludge Microcosms

“…However, the mass action model proposed by Levin et al is not applicable for matings with resting cells, such as in our shakingflask experiments (13). In the wastewater microcosms it is difficult to calculate actual transfer frequencies, since the growth rate of the transconjugants in the microcosms would have to be known, and the presence of flocs complicates the estimation of cell-to-cell contacts (27). Therefore, transfer frequencies for the clc element in the liquid matings or wastewater microcosms were not calculated.…”

“…This period probably reflects the chance for transconjugants to arise at such relative low donor and recipient cell densities. Mathematical approaches have been made to investigate kinetics of plasmid transfer in liquid matings (13,27). However, the mass action model proposed by Levin et al is not applicable for matings with resting cells, such as in our shakingflask experiments (13).…”