A generalized model of plasmid replication

Abstract

A simple model is developed that permits the determination of cellular extrachromosomal DNA content for a large number of host-plasmid systems. The model incorporates host, vector, and environmental influences on plasmid replication through the use of empirical expressions. The model successfully predicts the plasmid content of many host-vector systems in a balanced growth situation, both in continuous and batch cultures. Techniques for determining model parameters are also presented. The model parameters, which characterize the effect of plasmid on its own synthesis, are given physical interpretation through the development of a structured model for a particular class of plasmids and subsequent comparison of the predictions of the two models. The simplicity of the model expressions should, in the absence of: (1) discriminatory criteria such as plasmid concentration under transient growth conditions or (2) detailed knowledge on molecular mechanisms of plasmid replication, prove useful in the study of host-vector systems for genetic engineering applications.

Mathematical simulation of the growth of a three plasmid harboring Escherichia coli JM109 strain and the production of the fusion protein EcoRI::SPA with a four-compartment model

“…At high dilution rates no oscillation occurred, the production plasmid was stable as a function of the cultivation (generation) time, but the plasmid level was low, as observed by several other research groups as (well [1,4,20,39]. Under these conditions the process variables were constant in the second (production) reactor at cultivation times larger than 4 h. A comparison of the two runs, at D 2 0.79 h A1 and at D 2 0.95 h A1 shows that the concentrations of cell mass, glucose, acetate, the three plasmids and the three recombinant enzyme proteins have very similar courses as a function of the cultivation time ( Figs.…”

“…Later on, the in¯uence of the plasmid copy number on the decreased cloned gene stability was included into the model as well [32]. The plasmid replication was separately modeled by Lee and Bailey [17], Satyagal and Agrawal [39] and Greenhalf et al [10]. Cultivation of recombinant E. coli was modeled in a twostage continuous culture by Lee et al [20].…”

Studies on growth kinetics and plasmid stability of a recombinant Escherichia coli expressing a Schistosoma mansoni antigen

“…Plasmid instability can be structural through modi®-cation of the plasmid DNA or segregational by the generation of plasmid-free cells during the fermentation, and is in¯uenced by the type of plasmid, host strain used for transformation and environmental factors (Satyagal and Agrawal, 1989). The speci®c growth rate is higher in plasmid-free cells and, in the absence of selective pres- sure, the number of plasmid-containing cells decreases, establishing a mixed population of cells harboring plasmid and cells with no plasmid (Davis and Roger, 1998).…”

Towards Increasing the Productivity of Lignocellulosic Bioethanol: Rational Strategies Fueled by Modeling

“…Metabolic burden is ascribed to the lower availability of internal resources for host cells because the same resources are competitively used by plasmids for their replication and more importantly, the synthesis of exogenous proteins. While several empirical correlations are available to consider the change of growth rate with the plasmid content (e.g., Lee et al, 1985;Satyagal & Agrawal, 1989), cybernetic models are able to directly take into account of the reduction of internal resources (b), for example, as follows:…”