ABSTRACT
A vast number of experiments begin by inserting a plasmid into a type of cell in which it will express-this may be Escherichia coli or other bacteria, yeast cells, or mammalian cells of many different types. Some experiments are readily performed by expressing the genes of interest in E. coli. These include studies of gene regulatory networks such as the "repressilator", where the interactions among mutually repressing or enhancing promoters can be studied. For some types of biophysical experiments, expression of genes in bacteria other than E. coli is desired. Plates showing growth of mold or unknown bacterial colonies should be discarded into an appropriate biohazard disposal. Once the right plasmid has been obtained and the gene of interest cloned into it, it must be delivered to the bacterial cells. Yeast cells combine the ease of culture that characterizes microorganisms with the ability to express and correctly post-translationally modify complex proteins.
