"It has remained somewhat mysterious how bacteria are able to organize and spatially segregate their interiors and membranes," said Liphardt. "Two cells which are biochemically identical can have very different behaviors, depending upon their spatial organization. With new technologies such as PALM, we are able to see exactly how cells are organized and relate spatial organization with biological function."
In the PALM technique, target proteins are labeled with tags that fluoresce when activated by weak ultraviolet light. By keeping the intensity of this light sufficiently low, researchers can photoactivate individual proteins.
"Since individual proteins are imaged one at a time, we can localize and count them, and then computationally assemble the locations of all proteins into a composite, high-precision image," said Liphardt. "With other technologies, we have to choose between observing large clusters or observing single proteins. With PALM, we can examine a cell and see single proteins, protein dimers, and so forth, all the way up to large clusters containing thousands of proteins. This enables us to see the relative organization of individual proteins within clusters and at the same time see how clusters are arranged with respect to one-another."
Liphardt and his colleagues applied the PALM technique to the E.coli chemotaxis network of signaling proteins, which direct the movement of the bacteria towards or a
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory