The idea of Ice-9, although fictional, has always fascinated me. Its properties are so powerful, so influential, that one "seed crystal" can direct its entire surroundings, freezing oceans. A recent discovery of one component of the cell wall of bacterium reminded me of this effect. Let me explain.
First:
Ice-nine is a fictional material appearing in Kurt Vonnegut's novel Cat's Cradle. It is supposed to be a more stable polymorph of water than common ice (Ice Ih) which instead of melting at 0 degrees Celsius (32 degrees Fahrenheit), melts at 45.8°C (114.4°F). When ice-nine comes into contact with liquid water below 45.8°C (which is thus effectively supercooled), it acts as a seed crystal, and causes the solidification of the entire body of water which quickly crystallizes as ice-nine. A global catastrophe involving freezing the Earth's oceans by simple contact with ice-nine is used as a plot device in Vonnegut's novel.
A research group at Harvard and Princeton University reported a component of the bacterial cell wall that exerts enormous influence on the cell's ultimate shape. Think of "MreB cytoskeleton" as the world's tiniest conductor, directing a symphony for thousands of bacteria/musicians. Even more intriguing: a "left handed" molecular framework creates a "right handed" cellular structure. This is a brilliant study! From their Abstract: {excerpted for clarity}
The regulation of cell shape is a common challenge faced by organisms across all biological kingdoms. In nearly all bacteria, cell shape is determined by the architecture of the cell wall. In addition to shape, cell growth must also maintain the wall structural integrity. Robustness can be accomplished by establishing a globally ordered cell-wall network, although how a bacterium generates and maintains order on the micron scale using nanometer-sized proteins remains a mystery. Here, we demonstrate that left-handed chirality of the MreB cytoskeleton in the rod-shaped bacterium Escherichia coli gives rise to a global, right-handed chiral ordering of the cell wall. Local, MreB-guided insertion of material into the peptidoglycan network naturally orders the glycan strands and causes cells to twist left-handedly during elongational growth. Through comparison with the right-handed twisting of Bacillus subtilis cells, our work supports a common mechanism linking helical insertion and chiral cell-wall ordering in rod-shaped bacteria. These physical principles of cell growth link the molecular structure of the bacterial cytoskeleton, mechanisms of wall synthesis, and the coordination of cell-wall architecture.
Why is this important? Because the more we understand about how bacteria replicate themselves, the better chance we have to kill them, before they get to us.
A version of this article was published at Dean's Corner at ScienceBlogs.
Follow Dr. Jeffrey H. Toney on Twitter: www.twitter.com/jefftoney
If there were ever such a thing that caused ice to form at a temperature above 100 degrees fahrenheit, then all creatures such as ourselves would very quickly freeze up solid, die, and go extinct.