Maintenance of some ColE1-type plasmids in chemostat culture |
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Authors: | I. M. Jones S. B. Primrose A. Robinson D. C. Ellwood |
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Affiliation: | (1) Department of Biological Sciences, University of Warwick, CV4 7AL Coventry, UK;(2) Centre for Applied Microbiological Research, Porton Down, Salisbury, Wiltshire, UK |
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Abstract: | Summary 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. |
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