Effect of a broad‐host range plasmid on growth dynamics of Escherichia coli and Pseudomonas putida

Host–plasmid interactions were studied for the broad‐host range plasmid, pTJS26, a derivative of RK2. To isolate host and plasmid contributions to the growth dynamics and plasmid stability, separate experiments were performed with host and recombinant cells for two different gram‐negative hosts, Pseudomonas putida and Escherichia coli , at two different temperatures, 30 and 37°C. At the lower temperature (30°C) the growth kinetics were not affected by the plasmid, but plasmid instability was observed. At the higher temperature (37°C) growth rates and yields were lower than that for the hosts, but the plasmid was stable. This behavior can be explained by a combination of two phenomena. First, the copy number control mechanism may be temperature sensitive and, second, plasmid segregation may be inefficient. For both E. coli and P. putida the growth dynamics of the recombinant system was dictated by the presence of the plasmid.