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Extend Your Understanding of the Bacterial Transformation Lab
Genetic transformation of bacterial cells involves the uptake of exogenous DNA into the host
bacterium. Transformation occurs in nature in certain types of bacteria and scientists have
exploited and enhanced this property in the laboratory. Transformation allows scientists to
move recombinant plasmids containing DNA from two or more species into bacterial cells to
produce many copies of the recombinant plasmid or to produce large amounts of the
recombinant protein(s). Through these technologies scientists use bacteria as mini factories to
produce specific DNA molecules and proteins. In addition to bacteria, a number of other cells
can be transformed by exogenous DNA, including yeast, nematodes, fruit flies, plants, and
mammalian cells. Production of recombinant DNA molecules or recombinant proteins in these
cells is an important tool with broad applications in basic research, biotechnology, and medicine.
Research Application – Determining Protein Expression Patterns in Living Cells
To understand the normal function of proteins scientists characterize the protein sequence and
3-dimentional structure; the other molecules the protein may interact with or bind to; the protein
activity (i.e., enzymatic, catalytic, structural, signaling, etc.); where the protein is located, or
expressed, within a cell or within tissues in a multi-cellular organism; and a broad range of other
properties.
To determine where a protein is expressed in a living cell or organism, scientists often use a
reporter. A reporter molecule has some characteristic that allows easy detection and
visualization. For example, the green fluorescent protein (GFP), normally found in certain
jellyfish, exhibits bright green fluorescence when exposed to specific wavelengths of light.
Researchers can construct recombinant DNA molecules containing GFP DNA sequences and
sequences from a gene of interest to determine where the corresponding protein of interest is
expressed. Once the recombinant DNA molecule had been transformed into a cell or organism,
the fluorescence emitted by GFP will co-localize with the protein expressed by the gene of
interest and thus serve as a tag indicating which cells are expressing the recombinant proteins.
Drosophila transformed with recombinant
DNA molecules containing sequences
from both the GFP gene and the
engrailed gene. The engrailed gene
encodes a protein involved in RNA
transcription. GFP serves as a reporter
indicating which cells in the fly normally
express the engrailed protein.
Image credit: Christian Dahmann lab website
mpi-cbg.de/research/research-groups/christian-dahmann.html