The "clanger cicada" can physically kill bacteria by poking and shredding them with tiny pointy structures that seem to look a little like an old fashioned cheese grater. Keep in mind that this happens at a very small spacial scale, so the relationship between objects is different than in normal human experience. Essentially, the membrane of a bacterium spreads itself over the pointy nano-spikes of the insect wing. This is a little like a failed "laying on the bed of nails" attempt, but where the force involved with the bed of nails is gravity, gravity has nothing to do with the bacterium interacting with the nano spikes. Also, the bacterium does not shred because the nano spikes pierce it. Rather, the bacterial membrane is stretched to breaking point and falls apart that way. From the write-up in Nature News:
The clanger cicada (Psaltoda claripennis) is a locust-like insect whose wings are covered by a vast hexagonal array of 'nanopillars' — blunted spikes on a similar size scale to bacteria (see video, bottom). When a bacterium settles on the wing surface, its cellular membrane sticks to the surface of the nanopillars and stretches into the crevices between them, where it experiences the most strain. If the membrane is soft enough, it ruptures...
Here's the model:
Not all bacteria are subject to this effect; it depends on the rigidity of the cell membrane.
Obviously, we want to make all doorknobs and toilet seats out of this stuff.
Pogodin, Et Al. 2013. Biophysical Model of Bacterial Cell Interactions with Nanopatterned Cicada Wing Surfaces. Biophysical Journal 104(4):835-840. The article was published on Feb. 19th in Biophysical Journal. Abstract:
The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria on contact based solely on their physical surface structure. The wings provide a model for the development of novel functional surfaces that possess an increased resistance to bacterial contamination and infection. We propose a biophysical model of the interactions between bacterial cells and cicada wing surface structures, and show that mechanical properties, in particular cell rigidity, are key factors in determining bacterial resistance/sensitivity to the bactericidal nature of the wing surface. We confirmed this experimentally by decreasing the rigidity of surface-resistant strains through microwave irradiation of the cells, which renders them susceptible to the wing effects. Our findings demonstrate the potential benefits of incorporating cicada wing nanopatterns into the design of antibacterial nanomaterials.
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Interesting... if only there were more bacteria that could be killed with pointy objects (Most can't, right? Otherwise skip the water and just get your needles...?)
The way that bacteria attach to things, which is what we are seeing here, essentially, could be used against them. Bacteria involved in UTI survive between bouts by attaching themselves to urinary tissues. Some chemicals are known to interfere with that and may thus reduce chance of infection (the thing in cranberry juice, proanthocyanidin).
I quickly add: cranberry juice is not known to be good at treating UTIs. The question is, does regular consumption of the juice reduce recurrence of UTI's in women who tend to get them easily. The available evidence suggests that this may be true, but it is not conclusively proven. The cranberry juice thing is more interesting because of what it reveals about how regular people as well as scientists react to incomplete information. See this: http://scienceblogs.com/gregladen/2010/08/13/does-cranberry-juice-help-…
can this surface be practically synthesised for practical applications?
#2
It's not the proanthocyanidins (a class of anti-oxidants) in the cranberry juice that prevents UTI bacteria from adhering to the bladder wall; it's mannose, a sugar that appears on the surface of human cells (hence the term, MANnose).
Cranberry happens to be high in mannitol, which converts readily to mannose, some of which is excreted in the urine. By eating cranberries, or cranberry extract, one's level of urinary mannose increases.
Once in the bladder, the aqueous mannose competes with human bladder cells for attachment to UTI bacteria. By reducing the number of available, unbound mannose binding sites on the UTI bacteria, fewer bacteria attach and can form biofilms. The bacteria are then excreted by urination.
One can "cut to the chase" and simply ingest powdered mannose sugar to achieve the same effect. Eating cranberries is not necessary, although they're likely to be more available than bottles of powdered mannose...
One of things that confuses this issue is the incorrect assumption that what's labeled as "cranberry juice" in the grocery stores actually contains cranberry juice -- or, mannitol/mannose, which is what's important. Typically, this is not the case, and if this were the basis of experiments to verify its efficacy, it will likely fail.
Another misconception is that cranberry/mannose is an effective treatment for UTIs. It is NOT. Once the UTI bacteria form biofilms on the bladder walls, it's "game over" -- you have an infection and it's too late.
Cranberry/mannose is only effective as a prophylactic against getting UTIs -- so it must be consumed regularly. Think of it like "birth control pills for UTI bacteria"... Skip your dose and you may have "unhappy result".
#3
It's already been proposed that carbon nanotubes can be used for a similar purpose: They are thought to have the potential of piercing bacterial cell walls/membranes, allowing their cytoplasm to "leak out", killing them.
Brainstorms, no, proanthocyanidins have the effect I described.
You may be right about mannose, but I'm not vouching for that here. As far as I know, the mannose work and concentration is in other fruit juices.
You are certainly right about the issue being confusing,and confused by assumptions about what is being talked about. I addressed this here: http://scienceblogs.com/gregladen/2010/08/13/does-cranberry-juice-help-…
Greg, yes I provided comment 37 in that post.
I've never read that proanthocyanidins prevent bacterial adhesion, but I'll take your word on that.
Here's your confounder for UTI prevention: When my wife skips the proanthocyanidins by taking powdered mannose sugar instead of cranberries or cranberry juice (which have both), her UTIs no longer occur.
She is not willing to try only proanthocyanidins as a control. And I am not willing to return to the $200 bills for the 2am trips to the ER across town either.