Biology and Significance of PlasmidsA multi-talk discussion of extrachromosomal elements in microorganisms

Published January 2008 18 lectures
Emeritus Prof. Don Clewell
University of Michigan, USA

Genomic sequence data from numerous bacterial species is revealing that horizontal DNA transfer (genetic exchange between organisms) has played an enormous role in bacterial evolution. Plasmids, extrachromosomal DNA molecules able to replicate autonomously, are intimately involved in this process via their ability to facilitate cell-to-cell contact and intercellular (conjugative) transfer... read moreof DNA. In recent years plasmids have played a particularly significant role in the emergence of resistance to multiple antibiotics, and in many cases pathogenicity, associated with bacterial infections in humans. Because of their relatively small size, plasmids have also served as easily studied models for DNA replication and maintenance while at the same time illustrating great mechanistic diversity. In addition, plasmids have been very much involved as important tools in basic research in molecular biology (cloning, sequencing and genetic manipulation) as well as the biotechnology associated with genetic engineering and gene therapy.

The aim of these presentations is to describe some of the key properties of plasmids that have made them such important elements in our understanding and exploitation of many aspects of molecular genetics and evolution.