Thursday, June 20, 2019

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Dragonfly wings can rip apart bacteria without antibiotics - NanoTech Research


Special bacteria-killing surfaces constitute a highly active area of research and development. Strategies to construct them vary widely.

One group of researchers has infused a slippery surface with molecules that disrupt bacterial communication. Others have shown that silver nanoparticle coatings can destroy bacteria. Yet another group used black silicon to create a surface that resembled a tiny ‘bed of nails‘ (nanopillars), which physically rip bacteria apart.

That latter example, which falls into a broad category known as nano-textured surfaces (NTS), is of particular interest, because it also exists in nature. The nanostructure of black silicon is very similar to that of dragonfly wings.

And just like their elemental counterpart, dragonfly wings kill bacteria.

It is widely thought that a ‘bed of nails’ surface destroys bacteria through puncturing the cell wall. But in newly published research based on extensive use of various microscopy techniques, a team of Australian and Nigerian researchers demonstrated that an entirely different killing mechanism may be at play.

The first clue that the conventional wisdom was wrong came from the observation that nanopillars on dragonfly wings were not all the same height, as the photograph below shows:


This stands in contrast to synthetic ‘bed of nails’ surfaces, which tend to produce nanopillars of equal height.

A closer examination further demonstrated that the bacterial membrane does not come into direct contact with the nanopillars.

Rather, bacteria (in this case, E. coli) attach to the nanopillars via structural molecules secreted by the bacteria, known as ‘extracellular polymeric substances‘ (EPSs), which you can see in the image below, as well as by ‘finger-like’ extensions.



Once the bacteria land on the surface, they are subjected to adhesive forces. These can deform the bacterial membrane, but by themselves, probably do not cause the bacteria to rupture.

Instead, the bacteria are essentially caught in one of those sinister traps of which movie villains are quite fond. If they don’t move, the bacteria might survive.

However, when they do move, shear forces pull on the EPSs, ripping the membrane apart. This results in a fatal leakage of cellular contents, which causes the cell to deflate like a balloon, as you can see in the image below:


Only after the cell is dead do the nanopillars penetrate it.

The study has a few limitations. First, it was performed on E. coli, a Gram-negative bacterium with two membranes.
The authors should repeat their analysis with Gram-positive bacteria that contain only one membrane. Second, they should repeat their analysis using bacteria that do not produce as much EPSs to see if nanopillars are still lethal to them.
Finally, they should determine if synthetic nano-textured surfaces, which produce nanopillars of the same height, kill bacteria via the old model or via their new proposed mechanism.


Gaining insights into how nature works will invariably help those scientists wishing to mimic it. And it provides an interesting explanation for why dragonfly wings are so Clean.

Journal article:
http://pubs.acs.org/doi/abs/10.1021/acsami.6b13666


Story via American Council on Science and Health
http://acsh.org/news/2017/02/06/why-dragonfly-wings-kill-bacteria-10829


Source: https://myfusimotors.com/2017/02/09/dragonfly-wings-can-rip-apart-bacteria-without-antibiotics/

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New Movies in Theaters Opening This Week – June 21


Opening This Week – June 21


 
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84 Metascore
When a new toy called "Forky" joins Woody and the gang, a road trip alongside old and new friends reveals how big the world can be for a toy.
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Beneath Anna Poliatova's striking beauty lies a secret that will unleash her indelible strength and skill to become one of the world's most feared government assassins.
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79 Metascore
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102 min   -   Adventure
A family in emotional turmoil is taken by surprise in this quirky adventure where an eccentric 8-year-old American boy, Wes, has an existential epiphany - He believes that he is in fact a Mongolian goat herder.
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A teenager comes of age in a small Australian town during the 1970s when a 200-ton blue whale gets washed up on a local beach.
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91 min   -   Family | Sport
Fifteen year-old Taylor Collins is a golf legacy. The son of a PGA veteran, the younger brother of a PGA rookie, he has all the talent in the world-but wants nothing to do with golf or the pressure of being the next in line. After Taylor purposely blows his tryout for the school team, his disappointed father takes a drive that ends in a texting-while-driving accident and lands him in a coma. Taylor blames himself and, with the guidance of his brother and the prayer support from his mother Jenny and newfound crush Bailey, makes it his mission to get back on the team and become the first freshman in state history to lead his team to a state championship. Faith, hope, and love bring Taylor and his family closer than ever and he learns that the greatest way to honor his father and his God is to embrace the gifts and talents he was given.
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Source: IMDb https://www.imdb.com/movies-coming-soon/

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