Oscillators are huge in synthetic biology. They're an exciting challenge, very hard to make in a controlled, robust way, they have the potential to be useful in many applications, like well-timed drug delivery, and they can tell us a lot about how natural circadian rhythms work. A new paper in this week's issue of Nature from Jeff Hasty's group at UCSD presents a new synthetic biological oscillator in bacteria. While there have been a lot of oscillators designed in the past few years, this one is special because it couples oscillations in fluorescence to bacterial quorum sensing, allowing the oscillations to be synchronized in waves across a colony of cells. Quorum sensing is the way that bacteria communicate with one another, basically saying "hey guys I'm over here!" When a lot of these "hey guys" signals are combined in a dense culture, genetic switches in the bacteria are tripped, activating all sorts of behaviors. Synthetic biologists can engineer these switches to activate any number of "unnatural" behaviors in the colony. With some complicated designed genetic circuitry, the cells can be engineered to flash in sync.
Here is a gorgeous video of the bacteria growing and flashing, absolutely mesmerizing:
update: also check out the Nature video about this paper over at Grrlscientist's blog!
One of the important quorum sensing molecules is nitric oxide which is used to signal the transition between the biofilm phenotype and planktonic phenotype. High NO levels inhibit bioifilm formation by most heterotrophic bacteria, including many pathogens but it is low NO that inhibits biofilm formation in the ammonia oxidizing bacteria.
Many eukaryotes use interference with quorum sensing to control surface biofilms. I have found that ammonia and urea release though the surface can nourish an ammonia oxidizing bacteria biofilm, which then suppresses a heterotrophic bacteria biofilm (probably by NO and nitrite oxidizing quorum sensing molecules). Some marine organisms use haloperoxidases to make hypochlorite from H2O2 which is a good oxidant of some quorum sensing compounds.