I don’t like to admit that there are many things that are as badass in the marine world as sharks, but hagfish definitely give them a run for their money.
Hagfish are primitive, eel-like creatures that spend most of their lives slithering along the ocean floor, scavenging dead and dying fish. They’re spineless, virtually blind, have no jaws and have barely changed over the last 300 million years. They’re not sounding very tough right now, so what makes them so special? Well, hagfish have a sticky trick up their sleeves. When attacked or threatened, they exude a gelatinous slime into the water that can quickly smother the gills and mouth of a predator, thwarting the attack. This incredible goo has amazed scientists for decades, but we’re only just starting to understand its wonderful properties.
Hagfish slime is formed when seawater interacts with two different ingredients secreted by slime glands: mucin vesicles, which rapidly swell and burst in seawater, forming a gloopy net of mucus strands, and threads that are rich in a type of fiber called an intermediate filament (IF). These individual IF threads, which are produced by gland thread cells (GTCs), are only 12 nanometers in width but up to 15 centimeters in length. They’re arranged in yarn-like bundles called skeins which consist of around 15 to 20 conical layers of loops. As GTCs mature, the threads gradually increase in size, but they are organized in such a way that they can rapidly uncoil without tangling. When the skeins come into contact with seawater, the protein glue holding them together dissolves, causing them to unravel and release the elastic energy stored. This transforms a mere teaspoon of slime into a beaker-full of the stuff in just a few seconds.
Now that scientists are starting to understand the secrets of the slime, companies are attempting to synthesize it in the lab to create new super materials with a wide range of applications. One startup company for example, Benthic Labs, turned to the Hagfish with the ultimate goal of developing a biodegradable polymer made out of components of the slime itself. They think the slime could be used in everything from protective clothing to food packaging, bungee cords to bandages. That’s because hagfish slime threads have some impressive properties; they might be 100 times thinner than human hair, but they’re 10 times stronger than nylon.
To produce these materials, Benthic Labs intend on inserting hagfish DNA for the filament proteins into bacteria, transforming them into filament-producing factories. However, hagfish slime isn’t as strong as it is purely because of the filament proteins- lots of other factors are also involved. Furthermore, the unravelling process needs seawater. If the team can get around this requirement, then they may have a few interesting applications on their hands, such as airbags.
Spontaneous unraveling of hagfish slime thread skeins is mediated by a seawater-soluble protein adhesive
Hagfishes are known for their ability to rapidly produce vast quantities of slime when provoked. The slime is formed via the interaction between seawater and two components released by the slime glands: mucin vesicles from gland mucous cells, which swell and rupture in seawater to form a network of mucus strands, and intermediate filament-rich threads, which are produced within gland thread cells as tightly coiled bundles called skeins. A previous study showed that the unraveling of skeins from Atlantic hagfish (Myxine glutinosa) requires both the presence of mucins and hydrodynamic mixing. In contrast, skeins from Pacific hagfish (Eptatretus stoutii) unravel in the absence of both mucins and mixing. We tested the hypothesis that spontaneous unraveling of E. stoutii skeins is triggered by the dissolution of a seawater-soluble protein adhesive and the release of stored strain energy within the coiled thread. Here we show that, as predicted by this hypothesis, unraveling can be initiated by a protease under conditions in which unraveling does not normally occur. We also demonstrate, using high resolution scanning electron microscopy, that the treatment of skeins with solutions that cause unraveling also leads to the disappearance of surface and inter-thread features that remain when skeins are washed with stabilizing solutions. Our study provides a mechanism for the deployment of thread skeins in Pacific hagfish slime, and raises the possibility of producing novel biomimetic protein adhesives that are salt, temperature and kosmotrope sensitive.
The ultimate biofilament: Hagfish slime
(Phys.org) —Perhaps the worst fate to be had in the sea is to be slimed by the hagfish. The proteinaceous goo they secrete has gotten many a hagfish out of bind by gumming up the gills and suffocating a would be attacker. The slime’s prodigious strength and even more remarkable fecundity has attacked the attention of several scientists now trying to replicate it in the lab. While scientists are just begining to understanding how the so-called gland thread cells (GTCs) that produce the slime might actually work, others are already seeking to commercialize the slime as a high performance fiber.
Benthic labs is a synthetic biology startup comprised of students from the College of Science Engineering and Food Science (SEFS) in University College Cork. They envision slime as a material that could have uses in everything from clothing and body armour to applications in the medical field. They believe that the slime could replace many products that now ultimately derive from the petroleum industry. Slime is no slouch when it comes to material properties—on a weight basis it is five times stronger than steel. At 800 megapascals, it is nearly as strong as spider silk (1 gigapascal), which is made primarily from a similar intermediate filament (IF) protein. For those wanting to go full bio and build an all natural spidey-suit, we note that the strongest mussel-derived glue can only withstand 800,000 pascals (N/m2) on polar surfaces and 30 000 on non-polar. Slime based webs or cables would therefore be up to the job.
Each IF thread is a mere 12 nm wide but 15 cm long. Reminiscent of viruses which can pack huge lenghts of DNA into miniscule volumes, each thread is compactly coiled up into 15 or 20 layers inside of a single GTC. The thickness of IFs falls right between the two other main structural polymers found in cells, namely actin filaments (7nm) and microtubules (25 nm). The basic unit of the intermediate filament (IF) is an anti-parallel oriented tetramer. Unlike the parallel oriented actin or microtubule filaments, which have a plus end and a minus end, IFs lack any obvious polarity that would lend themselves to cell motility or directed intracellular transport.
The strategy at Benthic Labs is to put hagfish DNA for the slime filament proteins into a plasmid which is in turn put into bacteria. The bacteria then presumably produces the protein in huge amounts. If their product is to make it on merit, they are probably going to need more than an IF soup to get the numbers quoted above. Real biofibers like silk are more than fancy versions of the keratin IFs in our hair and nails. Many other proteins come into play as the fibers are mixed and formed. For hagfish slime, extremely rapid expansion not only key to building slime, it is the difference between life and death. In part, the volume building formula is facilitated by mucin vessicles. They are simultaneously released with slime to help generate the hydrodynamic forces for needed for unraveling.
There is also believed to be some kind of a seawater-soluble glue than is dissolved to release elastic energy stored in the fibers once the slime hits the water. In that way, just a few cupfuls of gland cell secretion containing some 25,000 thread fibers can rapidly turn into buckets of attack sauce. If the seawater requirement can be eliminated, we might see more terrestrial application emerge. For example, we could have the makings for a fantastic automotive airbag, provided one can deal with getting slimed. Like spider silk the road to replication and production may be long, but several folks are betting the obstacles can be surmounted.
If you were slightly unsure what a Hagfish looked like, well be unsure no more 😛
That actually makes me sad. How has no one made a Hollywood movie about the “Killer Hagfish”. If they have, please please, comment and let us know what that is called 🙂