Plasmid Transfer and Stability of Pseudomonas Cepacia and Enterobacter Cloacae in a Continuous Flow Culture System

Abstract

It has been proposed that utilizing bacteria with plasmid-borne genes which are eliminated naturally might be a relatively safe option for releasing genetically-modified microorganisms (GEMMOs) into the environment. The results of our research indicate that this might not be the case. In our flow-through column reactors, donor cells of Pseudomonas cepacia containing the transmissible plasmid R388::Tn1721 with genes encoding resistance to trimethoprim and tetracycline, passed these characteristics to recipients. Recipient cells were chromosomally resistant to nalidixic acid so that transconjugants were resistant to all three antibiotics. Plasmid transfer occured at relatively high frequencies but the plasmid, in both donor and transconjugant, disappeared exponentially from the thermodynamically open system. Thus, P. cepacia with R388::Tn1721 would appear to have the characteristics favourable for genetic release.