Video is, unfortunately, in German. If you don’t speak German, consider making up your own (PG) translations to key scenes and sharing them with us in the comments! : )

In the beginning you see the free-living amoebae (I think) happily wandering about on their own with some fungal filaments (called hyphae, high’-fee) growing at the top of the screen. Then the ameobae start aggregating — crowding after each other like sports fans filling a stadium. The species uses a famous signaling molecule called cyclic AMP (cAMP) to coordinate their union, and it passes through the swarms in pulsing, spiraling waves noticeable at about 1:35. If I’m using my extremely poor knowledge of German correctly, the narrator is nothing that hundreds of thousands of amoebae join together in the process. They do not fuse membranes; they retain their cellular identity.

Notice that some amoebae get left behind or lost in the process. At 2:47 you can actually see some break out of line and go back to being  little amoebae at the very tail end. After the spiraling and pulsating business is done, the mass stretches into a slug and crawls off. At some point between forming the slug (also called a grex) and making the sporangium (the house where spores are made), the amoebae get it on and mix some genes.

When the slug decides conditions are perfect, it stops, puddles up, and then stretches skyward. The lucky amoebae who will become spores riding up the stalk like an elevator. Those stalk cells get the rotten end of the deal — they must sacrifice themselves to ensure their comrades can reproduce. This little detail has led scientists to study these organisms in order to better understand altruism and cheating in nature. What they’ve found is that, as ever, things are not always as they seem. Some would-be stalk cells indeed give their lives, but others buck the system by cheating. Yet if everyone did, the system would break down entirely. There are, as you may imagine, some very interesting dynamics and mathematics governing this system.

Finally, a roving madsnail goes on a rampage wantonly destroying the beautiful slime mold gardens. Stupid animals.

Incidentally, D. discoideum is the species I wrote about in January in which some strains were recently discovered to practice agriculture, or something close to it, by taking bacteria of their preferred noshing type with them in their spores so they have a guaranteed food source when they land. And still more recently, scientists published an article in Science (see here and here) they may even have tissues — and use two signaling or regulatory proteins related to the ones animals use to organize their embryos during development. This seems to mean the common ancestor of slime molds and animals (whatever *that* might have looked like) was using ancient versions of these proteins to arrange itself, and its descendants — both slime molds, and you — inherited these same proteins and are still using them to organize their bodies, in their different ways.

Cellular slime molds represent one of life’s many experiments in multicellularity. You are the product of another. So are plants. And so are fungi, and brown and red algae and some blue-green algae — and there are many more. Other experiments seem to have been abortive; recently this article revealed that blue-green bacteria (aka cyanobacteria) dabbled in multicellularity many times. Remember: evolution isn’t a goal-directed endeavor, although in certain etremely successful groups (vertebrates, beetles) it may seem that way.

To see a different cellular slime mold species that makes violet sporangia on slime mold candelabra, see here. Spectacular.

Finally, I’d like to note I have a new favorite German word : Schelim. As in “schleim mold”. : )

HT to this post at Small Things Considered for the discovery of this wonderful and educational German film.

You are witnessing one of nature's most incredible migrations that never gets shown on the Discovery Channel. Believe it or not, each one of those little dots is a solitary amoeba. But not for long.

Note: This post contains a prize inside! It will await those patient enough to dig to the bottom. : )

Regular readers of this blog know well about my weakness for the protists formerly known as slime molds (scientists know apparently prefer the more PC and sexy “social amoebae”, although how you can get much sexier than “slime mold” I really don’t know). Exciting news came this past week that a species of cellular slime mold — Dictyostelium discoideum — contains members who have taken up bacterial farming (or at least husbandry — more on that distinction later). I ask again — slime molds: is there anything they can’t do*?

Before we get into their new status as potential FFA members, let’s talk a little bit about this particular group of slimes. So far on this blog, I’ve told you primarily about a group informally called “plasmodial slime molds”. This is the kind that make big, colorful slimy slicks that rove the forest floor wreaking microbial havoc as they vacuum up any bacteria, yeasts, and protists in their path, and then blossom into beautiful bright fruiting bodies like the one in the masthead of this blog.

But there is another kind of slime mold. One that, while perhaps less glamorous, is even more crafty and incredible: the dictyostelids, or cellular slime molds. What is the difference? Well, if plasmodial slime molds are amoebas that discovered living large, cellular slime molds are amoebas that discovered living social. In a plasmodial slime mold (also called myxomycete or myxogastrid), two amoebae meet, decide to spend the rest of their lives together, fuse, and then that fused cell starts dividing mitotically, or asexually, like it’s going out of style to churn out hundreds or thousands of genetically identical nuclei inside one big happy bag of cytoplasm.

In a cellular slime mold, something even more remarkable happens: a single amoeba called a myxamoeba suddenly decides it is starving. As a result, it secretes a molecule called cAMP as a distress call**. And suddenly, hundreds, thousands, hundreds of thousands of amoebae amplify the call by emitting their own cAMP, and begin streaming in toward Amoeba Zero in pulsating waves. They get sticky, climb on top of each other, and cling together. The pile towers up. And then, if it’s not sufficiently bright enough, the tower topples and begins sliming around like a slug. It’s now a single multicellular organism — made of 10,000 to 125,000 amoebae who still retain their individual membranes and identities. Yes, like the Borg — if they were all crazy-glued together. And if they intermittently all lived happily on their own before feeling an irresistible pull to join something called a “collective”.

Take a look at this process:

That aggregation star at left is a schematic of what you're seeing in the image at the top of this page. Tijmen Stam, IIVQ (SVG conversion) - user:Hideshi (original version) GFDL + CC-BY-SA, click image for link.

After crawling far enough to reach an area deemed suffienctly light (I imagine this it to raise the odds of being in a windy, spore-dispersally spot), the slug coalesces into a sombrero-shaped mass from which some of the cells begin gliding upward along a stalk like an elevator. At the apex, the elevator cells convert themselves to spores. Ultimately, they blow away in the breeze to (hopefully) more bacterial pastures.

Now take a look at this process in action.

• First, here’s an overview from my alma mater — the Plant Pathology department at Cornell (Try the downloadable versions if the player doesn’t automatically load or if you want to watch a high-res version (recommended)). Watch the perimeter and the background. Note slugs wandering about looking lost.

• Now let’s look at it up close — scroll down and press play on video at right. Note straggler amoebae.

And it gets better — or worse, depending on your perspective. Some of the amoebas in the slug must voluntarily sacrifice themselves (a process called programmed cell death, or apoptosis. It’s basically microbe seppuku) to form the long stalk. This seems to be determined primarily by what phase of the cell cycle they were in when they reached the forming slug; the last cells to arrive will form the tail of the slug, and the early-arrivers at the head of the slug will become the sacrificed cells of the stalk.

But in an entity where not all cells are genetically identical, you can see how it might be tempting (and much more reproductively successful) to shirk stalk duty and climb your way to the top come hell or high water — that is, to cheat. And in fact, it turns out cellular slime mold myxamoebae do sometimes cheat their way to reproductive success. Scientists fascinated by this have studied it a lot.

That brings us back to farming. Because in addition to being cheaters, some Dictyostelium also appear to plan ahead in other ways. Like packing lunch — or perhaps the seed of lunch. They bring their preferred bacteria with them and seed the soil where their spores land. It’s a little too early to tell if they just eat what they brought or wait sufficiently long for what they brought to reproduce a bit. But the evidence so far seems pretty conclusive: some D. discoideum spores are packin’ bacteria. Though whether they are packin’ them inside or outside the spore wasn’t entirely clear to me either. Only 1/3 of the samples they tested were farming amoebae, but that may be because it does come with a price. Farming amoebae are fitter in times of starvation, but less competitive than non-farmers in times of plenty. Having both strains around makes sense in a world of changing conditions.

Because they don’t weed, water, or fertilize their future food, some scientists suggest it might be better termed husbandry than farming. Whatever you call it, these are the first microbes ever known to do it. Cool***. And the reason, scientists told National Geographic, is that these are also the only microbes that are social — being social enables wind-blown, stalk-borne dispersal, which makes bringing bacteria worth it at all. And so far as we know, all the planet’s other farmers are all social organisms as well. EEEN-teresting.

From Science magazine’s writeup:

Koos Boomsma, an evolutionary biologist at the University of Copenhagen who did not work on the study, is not surprised that farming is scattered through the tree of life. “But if I would’ve had to predict where I would have next expected farming to be discovered, I would never have predicted a slime mold,” he says.

See, this is exactly what happens when we underestimate slime molds. And you all thought I was kidding about that world domination thing . . .

This discovery got full court press coverage; you can read more about it here, here, here, here, here, and here.

When first discovered, slime molds — both plasmodial and cellular — were thought to be fungi, hence the “mold” bit. But unlike fungi, they have cellulose cell walls (like plants and some other protists, but not chitin, like fungi) and cellular organelles called centrioles (like animals). Moreover, the two groups were not thought to be closely related to each other****. Now we know that although there are other types of slime molds that do not fit into these two groups, the plasmodial and cellular slime molds are true taxonomic groupings reflecting common ancestry, and that the two groups are fairly closely related: they are both in the same taxon as free-living amoebas — the Amoebazoa (look for the group on this tree, and then click on it to explore. Notice on the big tree they’re on the same branch with animals and fungi). Which makes sense — slime molds all begin life as ordinary looking amoebas.

Now bear in mind Dictyostelium, for all its transcendent coolness, is but one species among many — perhaps hundreds or thousands. What are other cellular slime molds like? Well, we may not know what many or most of them are like, since so few people study them. But below are videos (your treat for making it all the way to the end of this post) of a spectacularly beautiful other species of cellular slimes, Polysphondylium violaceum (Paul-ee-sfon-dil’-ee-um vie-o-lace’-ee-um — say that three times fast). Unlike Dictyostelium, it does not make roving slugs (though it does aggregate), and it uses a chemical called glorin, and not cAMP, as its chemoattractant. Watch the complex fruiting bodies — or sporocarps — form in these time-lapse movies again from my old buds in the Plant Path department at Cornell.  Notice in particular the branching and the purple pigment — it’s like a fireworks display in slow motion. Try pausing the videos just before the end for a nice still. And again, try the downloadable versions — they’re much higher quality images anyway.

• Video 1 — close up
• Video 2 — wider angle, different sample, even more spectacular display

Yes. Ameobas can do that.

Finally, ponder this: Dictyostelium, and the cellular slime molds as an entire group — was not discovered until 1935 in a North Carolina forest. 1935. Now ponder all the other amazing stuff that must still be out there, just waiting.

____________________________________________________________________

*Perhaps home decorating.

**cAMP is a ubiquitous Earth signaling protein found in organisms from humans to bacteria. It’s a stripped down ATP ( the energy currency of the cell) used, essentially, as one of several master switches for turning circuits (metabolic pathways) on and off in the bioreaktor/ Brownian chaos computer of the cell (Many, if not most, of the biochemical reactions of the cell are governed merely by the rate at which molecules happen to randomly bump into one another (implication: more molecules will make the reaction go faster). Even proteins chaperoned to important reactions by other proteins must bump into their chaperones in the first place.) In social amoebae, cAMP takes up the somewhat novel role of chemical attractant — that is, a pheromone.

***There are a few more lurid and/or fascinating bits to the cellular slime mold story. For one, lest you think their asexual reproduction was the only weird thing about them, Dictyostelium sex is also kinda creepy. It starts out normally: two amoebae meet and fuse. But things get weird fast: the zygote (diploid, or double-chromosomed) offsprings goes on a cannabilistic rampage, engulfing all nearby amoebae as fast as it can. When sated, the cell wall thickens with cellulose to form the resting spore, or macrocyst, that can survive tough conditions. Before it germinates, the cell undergoes meiosis, or reductive cell division, to get back to one copy of chromosomes per cell, and then several mitotic, or regular, cell divisions before it releases its little myxamoebas when conditions are good.

**** From my late-90s botany book: “The plasmodial slime molds, or myxomycetes, are a group of about 700 species that seems to have no direct relationship to the cellular slime molds, the fungi, or any other group.”

If all goes according to plan, this website will be making its move this weekend from frazer.northerncoloradogrotto.com to being truly hosted at theartfulamoeba.com (right now I employ masking to make that work). That may mean the feed will change and you will need to resubscribe, but I’m not certain yet as I have yet to consult with my volunteer tech department. Rest assured I’ll do my best to make the transition as seamless as possible, and the feed may not need any updating on your end at all. If for some reason it does stop working, just go to theartfulamoeba.com and hit the little orange RSS feed subscribe button at the upper right to resubscribe this blog to your feed reader.

In addition, if you have any links to my blog on your site, the links will break unless you sub theartfulamoeba.com for frazer.northerncolorado.grotto in the root once the transition happens. Finally, if you have a link to this blog in general from your blogroll, etc .(thank you! Very honored by that!), make sure the link is to theartfulamoeba.com and not frazer.northerncoloradogrotto.com

I’m making this move to make things less confusing for readers (what the heck is frazer.northerncoloradogrotto.com?!) and in preparation for some big changes: I hope to attempt join to the Nature Blog network and Researchblogging.org soon and I figured it would be best to get the tech stuff squared away before I complicate things further.

In any case, theartfulamoeba.com, artfulamoeba.com, theartfulamoeba.org, etc., will all continue working no matter what happens. Bear with me, faithful readers, and in the meantime, enjoy this movie of an amoeba strutting its stuff. This phenomenon by which amoebae move is called “cytoplasmic streaming“. I love that the amoeba seems to “change its mind” several times about whether that top pseudopod (arm) should be expanding or contracting. : )

In Russia, amoeba study YOU.

OK, giant deep-sea amoebae that roll around like possessed dust bunnies? AWESOME. The 411. Though this group had just been discovered in the Arabian Sea in 2000, it seems it was still a surprise to find them *leaving tracks* (although I should emphasize no one can actually see them move in real time. This sounds like a job for the BBC’s magic time-lapse camera). They are testate amoebae, or ameobae that make shells called tests (a few other deep sea protists like foraminifera also make shells called tests, and I just discovered that Chris Taylor over at Catalogue of Organisms just happens to have coincidentally published on the foram version yesterday.). This species, Gromia sphaerica, fits into the Gromiidea on this tree. Just look at all the uncharted territory and things you’ve never heard of. Space is not the final frontier. . . not by a long shot. Not yet.

The bigger, non-motile existing deep-sea protozoans Matz refers to in the video are probably xenophyophores, an outrageously bizarre group alluded to here before. You’ll just have to wait on a post about those another day. And there’s probably lots more giant deep sea protists I don’t know about yet. Readers?

The big take-home message of Matz’s discovery (or at least what they’d like us to take home) seems to be that we could really be misinterpreting Pre-Cambrian fossil trackwaves — that is, the fossil tracks of organisms that predate the blossoming of most modern animal groups in an event called the Cambrian Explosion, ca. 550 million years ago. These tracks can be found in fossils as old as 1.8 billion years (yes, that’s billion with a pinkie to the corner of the mouth). These tracks were for many years interpreted as early modern animals for whom we just didn’t happen to have fossils. But what if they were giant protists? Or something else? Possible, and probably not surprising given the fossils we do have of Ediacaran creatures, they bizarre early animal(?) forms that predate the Cambrian explosion and are the first fossils of complex multicellular organisms we have. They all seem to be soft and, for lack of a better term, pillowy. Yes, like Charmin.

Will we ever know? Probably not. But you never know. A fossil of a recognizable ancestor of a modern animal keeled over at the end of one of these tracks might settle things. On the other hand, simple tracks do tend to look alike. And with hundreds of millions of years on hand, there’s plenty of time for lots of really weird things we’ll never know about to have made them.

You know what this video reminds me of, of course . . .

I think you all know how I would answer that question.

Pollen from sunflower, morning glory, hollyhock, lily, primrose, and castor bean plants. 500X magnification; the bean-shaped pollen grain at lower left if 50 micrometers (μm) long. Believe it or not, these microbes are actually an entire plant -- the male gametophyte.

This blog is all about the variety of life, but part of that variety are the enormously different scales at which life can exist. You may know blue whales are the largest animals (ever, actually. Ever.), but they are not the largest organisms. Trees (aspen are notorious for this — one called Pando in Utah in paticular), fungi (remember the humongous fungus?), and perhaps a mediterranean sea grass called Posidonia oceanica can grow to many square kilometers courtesy their ability to grow asexually and keep at it for thousands of years. Life exists in a contiuum from these titans all the way down to the tiniest bacteria and archaea, the smallest of which are in the 200-400 nanometer range, round about the size of the measles virus.

Now the University of Utah has created an animation with a simple slider bar that takes you from coffee bean to carbon atom and back again. Check it out! Notice, for example, the amoeba (yay! Our site mascot!) approaches the size of the grain of salt and is visible to the naked eye when the animation is zoomed all the way out. If I were a bacterium or yeast cell, I’d cower too!

Notice also that mitochondria, the descendants of bacteria engulfed by ancestral eukaryotic cells (all cells except bacteria and archaea) billions of years ago, are actually slightly bigger than, but still more or less the same size as, E. coli. Notice that measles virus next to it — which gives the scale for the tiniest known cells mentioned above. Zoom in and out to compare this to the size of the amoeba or paramecium, and think about the fact they are both what we call “single-celled organisms”. Yet if the biggest amoeba or smallest bacterium had eyes, they probably wouldn’t be able to see each other. They are an order of magnitude (1000 times) different in size — and the difference is 10 times the difference between blue whales and us!

Don’t miss the question at the bottom either, which shows what amazing packers you boys are. A sample:

How can an X chromosome be nearly as big as the head of the sperm cell?

No, this isn’t a mistake. First, there’s less DNA (half as much, actually –jf) in a sperm cell than there is in a non-reproductive cell such as a skin cell. Second, the DNA in a sperm cell is super-condensed and compacted into a highly dense form. Third, the head of a sperm cell is almost all nucleus. Most of the cytoplasm has been squeezed out in order to make the sperm an efficient torpedo-like swimming machine.

Why do I get the feeling that last sentence will inordinately please the gentlemen out there? : )

The poor little guy who gets it in this video is a little ciliate flagellate(single-celled organism with a long propeller-like propulsive tail) named Chilomonas, according to Psi Wavefunction (thanks Psi!). This little drama is one example of the billions of such daily struggles that go on every day in the soil and water all around you. With our daily lives so full, it’s easy to forget.

This process of eating by engulfment is called “endocytosis” by biologists, which is a fancy term for “into the cell”. Specifically, this is “phagocytosis”, or cellular eating. Many cells can also perform pinocytosis, or cellular drinking, where cells can ingest small bubbles of water. Plasmodial slime molds (oft mentioned and beloved at this blog) start out as single amoebae like this, doing pretty much this the exact same thing in the soil. When they fuse to form a plasmodium, they’re feeding the same way — just at 5 Jillion X.

I love the smell of cyanide in the morning. Smells like . . . Desmoxytes.

Because nothing says, “Don’t Eat Me!” quite like a neon pink millipede (unless you’re two, in which case it says, “All You Can Eat Candy Buffet!”), I give you: The Pink Cyanide Millipede.

In addition to its easily pronounceable Thai (Mangkorn chomphoo) and Latin (Desmoxytes purpurosea) names, it features a pleasing almond aroma (courtesy of the cyanide it’s oozing).  Pink millipede saté sticks, anyone?

To see more bizarre animals either discovered or more fully investigated in the last few years (including our old friend the barreleye fish and the can’t-miss flesh-eating ghost slug), check out this gallery of bizarre animals over at New Scientist. You’ll be glad you did!

In the meantime, here’s a great picture of an artful amoeba, the gracefully named Chaos diffluens, which has officially dethroned my previous favorite scientific name, Borrelia burgdorferi (the spiral bacteria that cause Lyme Disease). If I were an amoeba and had a name this bad a**, I’d have it tattooed on my pseudopod.