Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Bacterium and Recombinant Plasmid
Name: Strait J.
Status: Educator
Age: 50s
Location: N/A
Country: N/A
Date: December 2002

Will a bacterium take up a recombinant plasmid if it already has one? If not, where do scientists acquire bacteria without plasmids for the purpose of taking up plasmids that have been engineered with a human gene?

A bacterium can take up several plasmids, provided these plasmids are 'compatible'. Plasmids contain certain genetic elements that prohibit the same host cell to take up other plasmids containing those similar elements, thus, they are incompatible. Sometimes it is required for the setup of an experiment that a bacterium contains two different plasmids, and that can only be done if two compatible plasmid types are chosen.

In most cases, the receptor host bacterium, say E. coli, is free of plasmid at the beginning of the experiment. Such well-characterized plasmid-free strains are available from (commercial) strain collections. Wild-type strains collected from the environment or from animal/human hosts frequently contain plasmids. There are experiments available to 'cure' the bacterium from the plasmid (select for cells without plasmids) but this is not always successful, especially when the advantageous properties of that plasmid are not known.

Trudy Wassenaar
curator of the Virtual Museum of Bacteria

Click here to return to the Molecular Biology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory