REHOVOT, Israel -- July 1, 1999 -- DNA becomes remarkably organized in bacteria that are subjected to various conditions of stress, Weizmann Institute scientists report in the July 1 issue of Nature. The tightly packed configuration of the DNA promotes the ability of the cells to withstand extreme environmental assaults such as oxidative agents and starvation.
This finding may one day allow the development of more efficient methods to fight bacterial diseases. In addition, if a link is found between the mechanisms allowing bacteria to survive under stress, and those that render bacteria resistant to various chemical agents, chemotherapy could be efficiently used against pathological bacteria which have become resistant to other types of antibiotics.
The Weizmann team, headed by Prof. Avi Minsky of the Organic Chemistry Department, discovered that bacterial DNA forms a crystalline organization when bacteria are exposed to harsh conditions. They further revealed that this highly ordered structure is formed by the mediation of a protein called Dps which strongly binds to DNA. The Dps protein, initially characterized by the group of Prof. Roberto Kolter at Harvard Medical School with which Prof. Minsky collaborates, is present at high levels in stressed cells. Within the ordered and tightly packed DNA-Dps structure, the DNA is very effectively protected against various assaults.
"In natural environments, bacterial life alternates between short periods of feast and long periods of famine and stress," Prof. Minsky said. "In order to survive, bacteria have evolved sophisticated mechanisms that allow them to protect themselves during starvation and stress, as well as to very rapidly resume growth when nutrients are again available. The ordered DNA structure may represent the ultimate mode of protection."
The scientists used X-ray and electron microscopy techniques to investigate the molecular structure of the complex made from the Dps protein and the DNA, and to better understand how this structure offers protection to the bacterial DNA. "We are currently investigating the actual signal that triggers the formation of the crystalline structure once subjected to starvation or stress and the signal that affects its fast disappearance once stress is eliminated," Minsky said.
"A rigidly ordered biological structure is generally considered to be incompatible with life. However, in living systems exposed to severe environmental assaults, intracellular crystalline assemblies may confer an efficient means for wide range protection. Indeed, ribosomes in brain cells of people suffering from dementia were found to form crystalline organizations. Moreover, DNA in sperm cells is highly ordered. We have now found this to be true in bacterial DNA as well and are trying to understand how general and significant the correlation between order and survival is," Minsky explained.
Accordingly, the Weizmann team has recently begun to study the correlation between the organization of DNA and fertility in human sperm cells.
The Weizmann Institute of Science, in Rehovot, Israel, is one of the world's foremost centers of scientific research and graduate study. Its 2,500 scientists, technicians, and engineers pursue basic research in the quest for the enhancement of the human condition. New ways of fighting disease and hunger, protecting the environment, and harnessing alternative sources of energy are the Weizmann Institute's highest priorities.
Weizmann Institute news releases are posted on the World Wide Web at www.weizmann.ac.il, and are also available at www.eurekalert.org.
Journal
Nature