Maintenance of some ColE1-type plasmids in chemostat culture

Abstract

When cells carrying the plasmids RP1, pDS4101 (a ColK derivative) or pDS1109 (a ColE1 derivative) were maintained in chemostat culture in the absence of antibiotic selection, plasmid-free segregants were not detected after 120 generations of nutrient-limited growth. By contrast, plasmid-free segregants of pMB9- and pBR322-containing cells arose after approximately 30 generations, irrespective of the host genetic background. However, even though pDS1109 was maintained its copy-number fell five-fold during 80 generations of limited growth. It is suggested that loss of pBR322 occurs following a similar copy-number decrease which results in defective segregation of the plasmid to daughter host cells. This defective segregation was not complemented in trans by either RP1 or pDS4101.

Investigation of the Effect of Growth Environment on the Stability of Low-copy-number Plasmids in Escherichia coli.

“…Hence studies of the stability of plasmids such as pAT153 and pBR322 have produced contradictory results, some of which are probably attributable to the use of different host strains (Jones, I. et al, 1980;Noack et al, 1981;Jones & Melling, 1984;Primrose et al, 1984;Caulcott et al, 1985). The properties of the plasmid itself are also important.…”

“…Glucose, phosphate and magnesium limitation in continuous culture have all been shown to reduce the stability of various plasmids (Godwin & Slater, 1979;Jones, I. et al, 1980;Noack et al, 1981 ;Jones & Melling, 1984) although no single limitation affected all plasmids tested. Nitrogen limitation was shown to have little effect on the stability of pBR325 (Roth et al, 1980;Wouters etal., 1980;Noack etal., 1981).…”

A nonlinear technique for the analysis of plasmid instability in micro-organisms

“…This will occur, for example, where the copy number of the plasmid varies considerably (Jones et al, 1980), or where plasmid or cell mutations arise during the experiment (Helling et al,198 1). In the analysis of biological data by the two fitting techniques, very different conclusions about the nature of the instability of the plasmid-bearing strain are reached.…”

Modeling the behavior of plasmid‐harboring cells in nonselective media

“…Parameter values used in simulation of model equations in (5) this study to describe production of cloned-gene protein is one applicable to a constitutive gene whose extent of expression increases with specific growth rate (f(crp) = 1). This choice is influenced by the simplicity of the expression and, also, because there exist some data on the product of such a gene, namely, p-lactamase, to compare the trends predicted by the model.…”