title: 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.
mesh_terms: D002455:Cell Division; D003470:Culture Media / Q000494:pharmacology; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics* / Q000648:ultrastructure; D005816:Genetic Complementation Test; D010957:Plasmids; D013997:Time Factors
chemical_list: D003470:Culture Media