Watching Mold Grow

This Stemonitis fusca, a funny-looking slime mold. It eats dead wood through its feet and grows itself long legs.

Trying to find out what causes the rather drastic color changes has turned up a few old stodgy books full of interesting descriptions. In short, each color change is connected to a different life stage. The white stage is the days full of vim, vigor, and juiciness. When they turn black, they are drying out, spores filling up the darkening heads until POOF! Apparently they release a mass of spores that’s not really visible in the above video.

They’re still good reads, so take a look.

From Hardwicke’s science-gossip: an illustrated medium of interchange and gossip for students and lovers of nature, Volume 12 , (p.113), published in 1876:

In the month of May he noticed upon the same stump some small masses of a white substance resembling blanc-mange, irregular in form, as though dropped there out of a spoon. Three hours later the surface of the substance had assumed a vein-like appearance, somewhat swelled and interlacing, which soon changed to regularly formed granulations…a visit a few hours later showed a complete transformation, for the whole mass, with the exception of the slimy film, appeared to be lifted bodily up, and supported underneath by numerous closely-packed horse-hair-like stems, the mass being thicker…In the course of the night…they resembled a nodding plume of feathers; the colour now being dark brown, and the outer membrane bursting, the whole soon became a dusty mass of spores.

From The natural history of plants, their forms, growth, reproduction, and distribution by Anton Kerner von Marilaun, (p.572), published in 1894:

The slimy protoplasm of Stemonitis fusca…rises up in the shape of numerous closely-compacted strands about 1 1/2 cm. long. Each individual strand is divided into a lower, stalk-like portion, and an upper, thick, cylindrical body. This is at first of slimy consistency, but soon becomes dry and divides into a central axis, from which proceed all round an endless number of very fine reticulating threads which break up into thousands of powdery spores, and at the periphery into a very delicate skin, which later on ruptures and allows the spores to fall out. This entire shaping of the protoplasm, with which is connected a change of colour from white to purple, is accomplished under the eye of the observer in about ten hours.

Why We Quest for Synthetic Skin

Skin--and wounded skin.

Whoever arranged our bones and joints was an architect. Whoever networked our veins and organs was an engineer. Whoever covered it all with skin was an artist.

Skin is simultaneously a disgusting and beautiful organ, punctuated with pores and moles and scars, filled with oil and sweat, but textured uniquely with smoothness, roughness, scales, feathers, hair, all colored warmly with traces of sunlight. Nothing in nature can match how supple, versatile, and integral to our well-being and awareness skin is, and nothing in nature can really replace it.

Our skin is the first line of defense against the elements, deflecting dirt and disease simply by being there, while simultaneously allowing oxygen flow in and carbon dioxide out. It also keeps our innards in order, insulating us and keeping us warm by (sometimes inconveniently) storing fats and water. And just under the surface, our skin is wired with nerves that inform our brain where we are, what temperature it is, and whether or not there is a damn needle stuck in the covers somewhere.

Touch is the main function of skin that we most immediately appreciate. The silky slither of a bed sheet across your arm or leg, the sun-warmed roughness of a rock you’re scrambling over, or the crisp, gentle bite of the autumn wind tweaking your nose–the list can go on. Unlike our ears or eyes, our skin covers our entire being. We are drenched in tactile sensations, from head to foot, with each nerve combining to tell a unique, sensual story about our setting every second.

Being Thin-Skinned: Simply Human?

Say something traumatic happens to your skin. A knife slices your palm, the gravel path you tripped on scrapes your knee. Take it a step further: a bullet blasts through your meager defenses, or the blaze that took your house sears you raw. Every nerve that titillates you on a good day can end up screaming in unison, and their demands for soothing silence will reverberate in your voice.

The degree of damage depends on how many layers of skin has been effected. Mammalian skin, like us humans, are composed of two layers: the epidermis and the dermis. The epidermis is the pretty wrapping paper we see every day, and it’s not a very thick layer at all. It doesn’t even contain blood vessels, so if you have ever nicked yourself accidentally in the kitchen, you know that it doesn’t take too much to disturb this outer layer. The dermis, however, is thicker and houses the nerve endings that deliver sensation to our brains. This layer is further divided into two regions, known as the papillary and the reticular areas. The reticular region is the deepest layer of all. Here, our hairs are rooted, as well as our sweat glands and veins, and the layer is thick with specialized proteins that give our skin its elasticity and strength.

In the language of burns, a first degree wound damages the epidermis. A light second degree burn reaches the first section of the dermis, while a slightly worse degree extends to the reticular region. A third degree burn affects the entire dermis, and a fourth degree burn takes out the skin entirely and proceeds to our tissues, muscles, and bones. At this point, you clearly have bigger worries than scars, but for (comparatively) lesser burns, any damage to the dermis will result in scarring, while damage to the deep reticular region requires skin grafts.

A Record of Trauma

Scar tissue is different from your original, undamaged skin. As the skin begins to grow back, your body-collagen, one of the main building blocks of skin. This means scars actually reach a point where they look and feel like regular skin, and then go on to become the noticeably tougher, thicker scar tissue over time. Additionally, collagen fibers in normal skin are arranged rather haphazardly–which is actually better than the neat, rigid Crayon-box arrangement in scar tissue. So though the material (collagen) used is the same, the amount used and the assemblage is different.

Why does scar tissue form? Why doesn’t our skin grow back the way it used to be? Well, the construction companies between the before and after are different. The original team is known as fibroblasts, while the guys who take over after the trauma goes by myofibroblasts. Myofibroblasts are halfway between a regular fibroblast and a smooth muscle cell. They get employed in wound healing because the edges of your wound need to move in, across the wound, to finally meet and become whole again. Myofibroblasts provide the contraction mechanism needed to make this happen.

Fibroblasts have instructions to keep producing all the materials and fibers that the existing surrounding tissue needs to maintain its function. Among the materials they constantly secrete is collagen, and myofibroblasts try to multitask by contracting the wound edges closed AND producing the collagen necessary for new skin formation. However, as we have seen, they produce too much, and they arrange it all in a new, strange way that creates a completely different building than before.

And, really, if you asked someone why they rebuilt their house to be tougher and stronger than before, would you really blame them if they said, “Because I don’t want it to be hurt that badly again”?

Hiding Past Pains

So why do we bother with skin grafts if our skin is capable of fixing itself? Skin grafts are necessary for large wounds that penetrate the reticular region of the dermis. Grafts speed healing, prevent infection, and improve aesthetics. Here’s a strange thing about our skin: if you place healthy skin on area that’s missing skin, your body will incorporate it into the healing process. It’s an organic bandage that simply becomes a part of you. The process of applying a fresh patch of skin from one area to another is fairly intuitive and grody to think about if you’re not a healthcare professional or a skin graft patient, but at the same time, it’s incredibly lucky for most people that our bodies can accept such a transplant. Skin that has been grafted from a healthy region will continue acting and looking like healthy skin–sweat glands and all. Only the edges will scar, as opposed to the entire wound area.

In some extreme cases, a patient may not have enough healthy skin to replace their burned skin. Doctors can choose to use an outside source of skin, be it an animal, another living human, or even a dead human. The disadvantage to this path is the same that plagues all recipients of organ donations: eventually, the body will blindly reject this foreigner, no matter how helpful it may have been.

Science looks to synthesize a skin replacement that will not hurt the patient more and will not be rejected eventually. So far, the two main solutions are artificial skin and skin cultures, which usually are used in tandem. Artificial skin products like Integra and Biobrane (and even a biomimetic alternative made from spider silk) act as the collagen matrix that myofibroblasts lay down during the healing process, which is like plopping the entire framework of a house down on a construction site instead of waiting for the workers to assemble everything from scratch.

Laying these fibrous, cloth-like products on a wound allows the patient’s cells to start building new skin faster, particular the crucial dermis layer that wouldn’t naturally grow back. This allows for the final skin graft sample to be thinner than they might have been or for skin cultures to be grown in a lab. Until recently, only the epidermis and superficial layers of the dermis could be grown in cultures, but now we are capable of growing full-thickness skin. The cultured skin would be applied much like a regular skin graft and can be supplemented with a skin cell spray that will help less severe wounds to heal.

The ultimate goal, however, is regeneration. How is regeneration different from healing? Well, look at a starfish. When an arm is cut off, it doesn’t simply heal–that would mean the arm wound would simply close up. Instead, the whole limb grows back, exactly as it was–which is precisely what we want to accomplish with skin grafts, as well as any kind of large traumatic wounds. Some people are fine carrying a record of their wounds on their faces or bodies, but others prefer to return to life as it was. Regeneration would make that otherwise impossible wish a reality.

While science unravels the cellular mysteries behind that, though, we can do little more than feel each sting of healing, and wait.

Zombie Worms and Vampire Bacteria–’Nuff Said.

Poor unfortunate souls.

Okay, zombie worms are not poor merfolk transformed into miserable worm people by a half-octopus witch lady, but they bear some resemblance to each other in that floaty, polypy kind of way. Zombie worms are actually fairly pretty, but they earned their colloquial name by dissolving whale bones for the lipid content in the middle with a plant-like root. The whales are dead already, so I suppose all in all, they’re very polite zombies.

The official genus name for these worms is Osedax, which means “bone-eating” in Latin, and according to Wikipedia, one of its nicknames is “bone-eating snot flowers.” However, it got into the news recently under “zombie worms” when a strain of this worm was found in the Mediterranean. They have been fingered as culprits in disturbing and warping the fossil record, but at the same time, the bulbous holes they leave behind in ancient fossils are now evidence that they existed three million years ago in that region. Osedax worms were first found in California, and since they are soft-bodied and leave nothing behind when they die, little is known about their collective past.

Here is an important balance of  appreciation: while whale fossils can be amazing records of the past, these worms are fairly specialized. They have been noted to occupy cow corpses when scientists wanted to see how specific their diet was, but sea cows don’t exactly fall to the ocean floor often. Their role in breaking down hard bone matter for other denizens of the dark waters is also crucial for the vibrant, ephemeral ecosystems that spring up from whale falls.

Micavibrio aeruginosavorus (purple) attacking a common bacterium Pseudomonas aeruginosa. M. aeruginosavorus does not actually have teeth, and P. aeruginosa does not actually bleed.

In the meantime, it may be a lot easier to appreciate the vampire bacteria, scientifically known as Micavibrio aeruginosavorus, whose genome has just been sequenced. M. aeruginasavorus has led a rough life, growing up in sewer water and learning to survive by essentially cannibalizing other bacteria for nutrients, amino acids, proteins, DNA, whathaveyou. It’s a survivor, a born hunter, and now that we know its genetic code, scientists hope to leash, train, and set this vampirical beast onto its human-hating brethren–including, amazingly enough, the bacterium that produces the thick mucus that plagues cystic fibrosis patients.

The “physiology” of these microscopic vampires is interesting. It is fully equipped to process carbohydrates, fats, and proteins, and it could create is own nucleotides. However, it lacks the ability to synthesize a whole mess of crucial amino acids, and is incapable of absorbing nutrients from its environment. Thus, if  scientists tried to culture the bacterium in a nutrient-rich environment without other bacteria present, it would starve to death. In the macroscopic world, this would be a bad sign if you put a sheep in a lush pasture and it only leveled blood-red eyes at you; doubly concerning if it salivated when you put other sheep in the pasture with it. As it is, when the scientists grew M. aeruginasavorus with other bacteria, it would latch onto the others and suck them dry of all the nutrients it needed.

Using this bacterium to attack the ones that hurt us is tantalizing. But we also have a history of being seduced by the promises of biological control and overlooking some element that lets things go horribly wrong (I always think of cane toads). Ecological control, however, is quite different from the microscopic field of diseases. Obviously, we’re keeping M. aeruginasavorus in its petri dish until we’re certain it won’t suddenly turn on us, and we will probably tinker with it a little to make sure whatever strain we willingly unleash upon ourselves will actually be the living antibiotic we are hoping for.

Still, this could be the grand opportunity for the zombie virus to spring up–from a vampire bacteria. That’s some good fictional irony just waiting in the wings.