DNA Crystallization in vivo

. Thursday, March 13, 2008

Bacteria are some of the marvelous creations of nature. They are known for their adaptability. The humble Escherichia coli that we find in almost all the microbiology and molecular biology labs continues to surprise us with its ingenius ways of handling problems.

Under extreme stress, bacterial cells are known to take many steps to protect themselves. Abraham Minsky of the Weizmann Institute of Science in Rehovot, Israel identified an interesting defense mechanism of E.coli thats slightly different. These unicellular organisms crystallize their own DNA.
This 'novel' defence strategy was found to be the responsibility of a protein called Dps. It resembles ferritin, an iron-storage protein found in humans.

Dps is produced when the cell experiences nutritive or oxidative stress. It binds to DNA (apparently without any specificity) and promotes its crystallisation. Earlier investigations revealed another important function of the Dps protein. It sequesters iron and other metal ions that may help in the generation of free-radicals.

DNA - Dps crystals

Minsky and his collegues genetically engineered a few bacterial cells to over-produce this protein. These cells formed DNA crystals more easily and starvation was sufficient to cause crystallization of DNA. This process was also found to be reversible. "Once nutrients are supplied, [the crystals] disappear within a very short timescale, and the bacteria are viable and growing," says Minsky.

Whats remains to be explained is, how the bacterial DNA integrates itself into a crystal!