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Bacteria Propel Themselves with Slime Jets
galactic_grub writes "Scientists have discovered that some bacteria propel themselves along using tiny jets of slime. According to this story on NewScientistTech, the researchers previously thought the slime was a lubricant. They believe the same technique could be used to move nano-devices around."
"Scientists have discovered that some bacteria propel themselves along using tiny jets of slime".
No - that has been known for a long time. This research mearly elucidates the mechanism. Which is nice. But, in addition to the slime nozzles at the back end, .
Did you know that at the front end Myxo bacteria have "grappling hooks" which that can extend and then retract? Search for pilus retraction...
Or that they are pack hunters? Or that they will commits suicide to save their buddies?
Myxobacteria - they're great!
You're assuming propellers work the same at nano scale. They don't.
;)
Remember, this is a realm of counter-intuitive phenomena that you can't just "gut feel" your way around.
Odds are good that if bacteria do it, then it's an extraordinarily efficient way to do things, and we should seriously consider it. Remember that
a) they evolve much faster than we do
b) are much older (predating eukaryotes by 2 billion years or so)
c) they live at the micro/nano scale boundary.
Call me when you've got that kind of experience under your belt
This may seem a very inefficient way to move about, but things work very differently on the lengthscale of bacteria.
For example, most moving bacteria use propellor-like objects (flagellae) to propel themselves, but the way they work is very different from propellors.
Propellors use Bernouilli's principle to create a pressure difference between the front and the rear of the propellor, thereby 'sucking' themselves forward.
Bacteria, because they're so small, live in a surrounding where water has an effective viscosity higher than molasses on our lengthscale (it has to do with a dimensionless number for friction in hydrodynamics called the Reynold's number, that scales with inverse length).
Bacteria have to push themselves forward in something that really doesn't want to move and creates a lot of friction; all kinds of movements that we would think of intuitively possible are impossible under these circumstances. For example, some hydrodynamics people talk about the 'scallop theorem', which states that at these conditions it's impossible something to move forward like a scallop: rapidly closing its shell and opening it again.
Most flagellae are either spiral structures or stiff rods that get swayed back and forth; none use Bernoulli's effect, but tend to make use of the high viscosity by pushing against the fluid.
These bacteria make a starch gel to propel themselves: the sugar concentration doesn't need to be very high to get a decent gel, and the speeds they obtain sound incredible (usually we're talking 10 microns per minute, not per second).