Name: Strait J.
Status: Educator
Age: 50s
Location: N/A
Country: N/A
Date: December 2002
Question:
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?
Replies:
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
www.bacteriamuseum.org
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.
