Monday, November 29, 2010

Ice-Nine, Or How to Grow Concrete from Bacteria

In Kurt Vonnegut's 1963 satirical novel Cat's Cradle, the protagonist follows the trail of a brilliant researcher's children who hold with them ice-nine - a chemical invention small enough to be carried under the fingernail, but potent enough to freeze all water on earth solid. The element is described as a "seed" that alters the atomic composition of liquid:
"There are several ways", Dr. Breed said to me, "in which certain liquids can crystallize - can freeze - several ways in which their atoms can stack and lock in an orderly, rigid way." That old man with spotted hands invited me to think of several ways in which cannonballs might be stacked on a courthouse lawn, of the several ways in which oranges might be packed into a crate. "So it is with crystals, too; and two different crystals of the same substance can have quite different physical properties."
He goes on to describe the stacking process:
The theoretical villain, however, was what Dr. Breed called "a seed". He meant by that a tiny grain of the undesired crystal pattern. The seed, which had come from God-only-knows-where, taught the atoms the novel way in which to stack and lock, to crystallize, to freeze. "Now think about cannonballs on a courthouse lawn, or about oranges in a crate again", he suggested. And he helped me to see that the pattern of the bottom layer of cannonballs or of oranges determined how each subsequent layer would stack and lock. "The bottom layer is the seed of how every cannonball or every orange that comes after is going to behave, even to an infinite number of cannonballs or oranges."
And of course, the prolific advantages are described alongside the horrific consequences:
And that old man asked me to think of United States Marines in a Godforsaken swamp. "Their trucks and tanks are wallowing", he complained, "sinking in stinking miasma and ooze." He raised a finger and winked at me. "But suppose, young man, that one Marine had with him a tiny capsule containing a seed of ice-nine, a new way for the atoms of water to stack and lock, to freeze. If that Marine threw that seed into the nearest puddle...?" "The puddle would freeze?", I guessed. "And all the muck around the puddle?" "It would freeze?" "And all the puddles in the frozen muck?" "They would freeze?" "And the pools and the streams in the frozen muck?" 'They would freeze?"
In 1963, Vonnegut pondered both the possibilities and the dangers of such technology through dark humor, the absurd, and the profane in this story of invention and the human hands that guide it. In 2010, however, the potency of this allegory is all to familiar as science, theory, and invention is constantly redefining the ability of humans to solve problems.

For the annual iGem synthetic biology contest, a group of students at Newcastle University have engineered BacillaFilla - a type of bacteria that, once inserted into a concrete crack with the proper growing media, will germinate and produce a "mixture of calcium carbonate, levan glue and filamentous cells" that will densify and "activate concrete repair". Eerily, the scientific name for the compound is called Bacillus Subtillus 168. According to the team:

BacillaFilla repairs concrete by producing a mixture of calcium carbonate, levan glue and filamentous cells in the cracks. Once we have applied BacillaFilla spores onto the concrete surface, they will start germinating in the presence of media. Once the cells have germinated, they will start to swarm down the crack. At the bottom of the crack when they reach a high density, they will use subtilin quorum sensing to activate concrete repair. BacillaFilla repairs concrete by 3 different processes:

1. Some of the cells with produce calcium carbonate crystals,
2. Some of the cells will become filamentous thereby acting as reinforcing fibres in the crack and
3. All the cells will produce Levans glue which acts as a binding agent and at the same time it fills up the whole crack.
Interestingly, the bacteria only work through a swarming process whereby the bacteria propel themselves to reach the point of germination. Also, almost in a pre-meditated response to detractors and grey-goo fear-mongers, the team has implemented a genetic "kill-switch" to stop the spread of bacteria.
Of course, the ability to repair concrete from within is as exciting as the potential for a runaway concrete-producing super-bacteria is alarming. Material technologies such as this blur the lines between natural phenomena and synthetic architecture, border on Utopian ideals and science-fictional dystopias, and represent bold new ideas in research and development.

Images via TeamNewcastle and Newcastle University. Seen on i09.