User blog:Cerne/Much ado about mushrooms

And no, I am not referring to the "magic" kind, here. Although they might seem quite magical at first. I am referring to a couple of articles I found on the Conworld Bulletin Board (CWBB) a while ago. The first one is an older article by EnvironmentalGraffiti.com called Mushrooms that Glow in the Dark and the second is a newer article by EcoGeek.org called Chernobyl Shrooms Devour Radiation. Both are examples of extraordinary adaptations taken by certain species of mushroom, and both provide some excellent real life inspiration for creating conworlds. In particular, they really help me with my own conworld.

The first article describes a type of mushroom called Mycena chlorophos which is found so far only in Japan and Brazil. They are bioluminescent, and while no one yet knows how these mushrooms are using the chemicals in their environment to produce the bioluminescence, what kinds of chemicals they are using, where they are getting the chemicals from, and why they have evolved toward becoming bioluminescent in the first place, one can assume that there are as-of-yet many different ways to answer these questions. Fireflies use bioluminescence to attract mates, so there's one purpose for bioluminescence. Many organisms living in oceanic abyssal zones use bioluminescence for communication. And there are bioluminescent plankton that are bioluminescent as a side-product of metabolizing metals in the surrounding environment. So it isn't hard to imagine some other reason why an organism might evolve toward becoming bioluminescent.

Of course, it must be noted that no organism strives toward a new adaptation until that adaptation has already evolved. What happens is that some sort of pre-adaptation unintentionally evolves in the organism first, as perhaps a byproduct of some other already-selected-for adaptation, or by accident, and then - once the organism does something with the new adaptation that is advantageous - it intentionally selects for that adaptation by being attracted to it in a potential mate. Organisms don't care what kinds of adaptations make them successful, and hence "sexy," to other members of their species and population; as long as the organism itself is successful in its environment and it is able to compete with other species and other members of its own species, then it will attract a mate and pass on all of the adaptation that have made it successful.

Therefore, we've got to figure out what the organism in question is already doing and how the new trait - in this case bioluminescence - can help the organism do it more successfully.

My conworld uses bioluminescence for a somewhat more sinister purpose. Like Earth, all fungi on the planet reproduce by releasing spores. Mushrooms aren't actually a type or taxonomic group of fungi, although only some types of fungi can produce mushrooms; rather, they are a phase in the lives of some fungi species in which macroscopic "bodies" are formed to release spores. Anyway, like Earth, there are also spore-producing plants on the planet. Unlike Earth (now), there is a much greater diversity of spore-producing plants, or sporophytes, in my conworld. This is because the delay in angiosperm seed-producing plants has allowed sporophytes to out-compete any possible gymnosperm predecessors due to the environments where most sporophytes are found being much more conducive to spore dispersal and growth than seed dispersal and growth. In addition, many fungi and sporophyte plants are epiphytes and/or parasitic, meaning their spores need to grow inside organic matter. Fungi in particular need to consume organic matter, instead of merely growing in it, so they need a way to get their spores into living tissue. For those species growing their spores in plant tissue, this is quite easy to do. However, some fungi spores need to grow inside animal tissue. One way they do this is by getting eaten. They grow "toadstools" structures much like many fungi on Earth do, but these structures have been adapted to look appetizing. They do this in a bunch of different ways, but since my conworld receives less sunlight than Earth does (due to a number of factors, from sun type to more cloud cover) it is darker during the day and night than Earth is. Many animals still need to see, so one way to attract them into eating you is by providing them with light. Providing certain smells, textures and shapes/appearances also helps, but in this way bioluminescence can play a major role in fungi reproduction. Bioluminescence also occurs in several sporophyte plant species in my conworld but not to such an extent.

The second article I actually found a lot more interesting. The type of mushroom is called Cryptococcus neoformans and it lives in the radioactively contaminated site of Chernobyl in Ukraine. It actually feeds off of nuclear waste and stores it in the body of the mushroom. Now, it should be pointed out that the mushroom does not neutralize the absorbed radiation or make it disappear. The nuclear waste is merely "relocated" into the body of a living organism. The article itself mentions that the mushrooms could even be used as a possible source of nuclear energy. Still, all that radiation did go somewhere. Right now, as far as we know, the mushrooms are just storing it. If they are using it somehow, the article certainly doesn't say anything about it. But what if an organism - like a fungus - could use radiation for its own purposes?

One of the complaints I have toward many conworlds (and the people who create them) that have mushrooms in them is that these mushrooms are very often treated like plants. They grow like plants, requiring only air, soil, and water. Of course we know that plants need these things in order to get all of the ingredients required for photosynthesis. What I think many conworlders forget is that mushrooms - and other types of fungi, for that matter - are not plants. Sure, they may look like plants because they are sessile (meaning they don't move) and they grow out of the ground, but fungi - all fungi - are heterotrophs. Meaning they need to consume organic matter in order to live. It might be dead or alive, but organic matter is organic matter. Heterotrophs cannot obtain energy from inorganic chemical compounds the way plants can. You need a way to break chemical compounds apart in order to get any energy from them, and fungi can't do this, so they - like many of the more simple organisms such as bacteria - need to take in chemical compounds as those compounds already are. Organic compounds are chemical compounds arranged in specific ways and involving specific elements like carbon, nitrogen, hydrogen, and oxygen. That is why we call them organic. They are the building blocks of all carbon-based life on Earth. Fungi can only obtain energy and nutrients from organic compounds, and these organic compounds come predominantly from dead animals and plants. So one very common question I have regarding...say...giant tree-like mushrooms of the sort you often see in popular fantasy nowadays, is where the mushrooms are getting their food from. Think about it: a mushroom the size of a tree is going to need a hell of a lot of organic matter in order to sustain itself.

Radioactive isotopes like potassium-40 and thorium-232 could certainly help an organism obtain chemical energy from existing compounds. I mean, UV rays from the sun and gamma rays from radioactive isotopes are both forms of radiation, right? After all, plants do it. The problem is not that these forms of radiation are not available. We're surrounded by sunlight for up to 12 hours each day whenever we go outside, for Pete Sake. You would think that if UV rays were all it took for us to sustain ourselves on inorganic chemical energy then we would be doing it by now. No, the problem is that animals and fungi don't have chloroplasts. We have mitochondria. Chloroplasts are the plant equivalent of mitochondria in animals and fungi, but they do things that mitochondria can't do. Chloroplasts can photosynthesize; they turn carbon dioxide molecules into sugars by splitting off the oxygen atoms and combining the carbon atoms with hydrogen. For the most part, they can do this because they have extra membranes - sometimes three or four - and a much reduced, simplified genome to minimize any damage done by sunlight, but it is not what allows them to photosynthesize. I don't have a degree in botany and a lot of what I got from my grade 12 biology class has probably been forgotten, but to know why these differences between mitochondria and chloroplasts are there to begin with, we need to go back in time and look at something called Endosymbiotic Theory.

Cyanobacteria, otherwise known as "blue-green bacteria," comprise the largest group of photosynthetic organisms on Earth - around 90% of oxygen production and carbon dioxide reduction is done by microscopic photosynthesizers like cyanobacteria and phytoplankton - and they have played perhaps the biggest role in the evolution of life on Earth by converting our planet's primitive carbon dioxide atmosphere into one composed of 21% oxygen (the other 78% is nitrogen and 1% is argon). At some point in Earth's evolutionary history, some prokaryotic cells started eating cyanobacteria while keeping them alive within the cell body. Since these were photosynthetic bacteria, any chemical energy they released could now be used by the surrounding cell. Thus, the first microscopic plants had evolved. Those early prokaryotic cells also ate other types of bacteria that could not photosynthesize but that could still produce chemical energy by combining inorganic chemical elements into compounds. When these bacteria were consumed, they eventually became mitochondria and the host cells became the first animals. We don't really know exactly what these other kinds of bacteria were, or if they even were bacteria; the closest guess right now is that they were some type of proteobacteria.

These differences between plant cells and heterotrophic eukaryote cells, like those found in fungae and animals, explain why - while the mushrooms in Chernobyl are taking in radioactive isotopes - they don't appear to be using the isotopes. At least not in any purposeful and/or systematic way. About four paragraphs back, I asked the question "what if an organism could use radiation to generate its own energy and nutrition?" Well, for starters, it would need to be an autotroph. Like a plant.

My conworld does have photosynthetic plants in it. They are a lot like the plants on Earth in their basic structure and anatomy. One difference is that because of the lower levels of sunlight, the colour of these plants is more of a yellowish-green colour, like olive, than the rich pure greens and blue-greens you see in most plants on Earth. Their leaves are thinner and more delicate to minimize the amount of leaf a ray of UV needs to pass through. Sporophytes also outnumber seed-producing or spermatophyte plants in diversity and number of species. Regardless of how diverse they are, however, they all photosynthesize using light from the planet's sun so they don't need radioactive chemicals to produce food. And there are fungi in my conworld, but they are all heterotrophs, as those on Earth are. Obviously none of the animals on my conworld can photosynthesize, either. At least none that I have planned can. They are all heterotrophs. Yes, my conworld has slime molds, and no, none of them can photosynthesize because all of them (or most of them - I haven't actually looked into slime molds very much yet) are heterotrophs, too.

So why does the article about radioactive waste-eating mushrooms in Chernobyl hold such a particular interest for me?

You may recall in one of my earlier blog entries that my conworld has five multicellular kingdoms of life that are macroscopic (you can see them). The fifth kingdom is a group of organisms that resemble plants. Like plants, they are sessile, and like plants, they are autotrophs. But unlike plants, they do not photosynthesize. Nor do they use chemosynthesis, as many methanogen archaea in swamps and sulphurophile bacteria in deep sea hydrothermal vents do. So what do they do? Yep, you guessed right. They use radiation from radioactive isotopes. This is not a relatively short occurrance in their evolutionary history, either, as it is for the mushrooms in Chernobyl. No, these organisms have been using radioactive energy throughout their entire evolutionary history on their (my) planet.

I wasn't intending to go extensively into the mechanics of my conworld's biology this early in my blog but in order to explain why the Chernobyl mushroom article was so significant for my conworld, I need to explain how the same thing going on with those Chernobyl mushrooms also goes on in my conworld with this fifth kingdom of life that I've devised.

Let' start at the very bottom, or more appropriately, the very beginning. Back to Endosymbiotic Theory. There have been a few bacteria that have been discovered which can survive in heavily-radiated environments. How heavily radiated? I don't know. All I know is that I have a big book on the natural history of Earth mentioning a type of bacteria that can live in irradiated environments. A similar counterpart exists in my conworld. It resembles cyanobacteria in anatomy but it lives deep, deep underground. It is an extremophile, and its predecessors produced methane in much the same way methanogen archaea do on Earth. However, because my planet's interior has a larger quantity and diversity of radioactive elements in it, such underground systems would be exposed to higher levels of radiation. So these bacteria evolve a resistance to it by systematically scanning their own genes - every one of them - and terminating when a genetic error is detected. They multiply at an accelerated rate so there will always be those that aren't harmed by the radiation. They also have membranous "shells" that slow down or deter the effects of the radiation. In time, these bacteria evolve toward using the radiation to separate carbon dioxide molecules instead of recombining them. They do this by actually consuming the isotopes, storing them inside their bodies as the isotopes decay, and fissioning before the bacteria's genes get damaged by the radiation. One bacteria takes the carbon molecule, the other takes the oxygen molecule and the decaying isotope. The isotope is consumed again, and the process continues. Now, assuming some of these bacteria lived a bit further away from the radiation, somewhere inhabited by early prokaryotes, endosymbiosis could occur. The new eukaryotic organism could effectively use their bacterial symbiont to produce energy and discard any damaged "sister" bacteria before their own genes are damaged.

Let us fast-forward to the time in these organisms' evolutionary where the first macroscopic organisms appear. They are now sessile, as perhaps their single-celled predecessors were, but they are now a whole lot more complex. I can now describe how the process of using radiation from radioactive isotopes could be used in a macroscopic organism as large as the mushrooms in Chernobyl are, but that is an autotroph instead of a heterotroph.

It all starts in the leaved. The leaves on these organisms are not like those of a plant. They are thick and spongy, and they sit on the branches much like the caps of mushrooms do. Their colours vary, depending on what kinds of chemicals they are absorbing from the air. Their default colour is dark mustard-yellow because they are made of polymerized sulphur that is saturated with hydrogen.

The process goes like this:

The first gaseous elements that are absorbed by the sponge-leaves are hydrogen and various halogens like chlorine. The halogens are combined with any free hydrogen to make acids like hydrochloric acid (HCl) which are then transported out of the leaves, through the branches, down the trunk, and into the "roots." There, it is used to wear away at the rock and obtain any radioactive isotopes within the rock like potassium-40. The roots then consume the isotopes.

Meanwhile, carbon dioxide is absorbed next. It is transported out of the leaves in "transporter cells" that take it down the trunk and into the roots. The transporter cells eat the isotopes once they are taken in, then fission. The carbon dioxide molecule is taken apart and one sister cell takes the carbon while the other takes the oxygen. The cell with the carbon also takes the isotope and goes back up to one of the leaves to combine it with hydrogen to create hydrocarbons. The hydrocarbons are used to create tissues and hormones like ethylene (C2H4).

The cell with the oxygen also goes back up to one of the leaves. If the oxygen hasn't combined already to produce O2, it is combined with any hydrogen that is absorbed and trapped by the leaves to form H2O (water). This produces a lot of chemical energy. The energy is transferred inside the cell to other parts of the organism.

Eventually the radioactive isotope decays to a pint where it is no longer radioactive. If the cell carrying it has free carbon inside it, it splits and one sister cell takes the carbon while the other takes the decayed isotope. I believe once some radioactive isotopes - like potassium-40 - decay, they turn into sodium or some other stable mineral. These can be combined with halogens taken in by the leaves to form salts which can then be taken back down to the roots and excreted into the surrounding soil or rock.

As mentioned earlier, the different "leaves" on the organism are different colours, depending on which chemicals they are taking in. Once sulfur is taken in, it goes into leaf composition right away unless it is part of a sulfur dioxide molecule. In the latter case, the sulphur dioxide is treated like carbon dioxide. Leaves that take in primarily carbon dioxide and sulphur are a dirty yellow colour. Leaves that take in mostly hydrogen are more reddish than yellow. Leaves that take in mostly halogens range from greenish yellow to pure green and even blue.

In the end, these autotrophic organisms are doing three important things: 1) they are removing harmful gases like sulfuric acid and chlorine from the air; 2) they are removing radioactive isotopes from the surrounding environment and actually doing something with them; and 3) they are producing and releasing water and oxygen. The organisms are also removing greenhouse gases, but this planet is farther away from its sun and therefore has a cooler average mean temperature globe-wide, so greenhouse gases are not nearly as much a problem on this world as they are on Earth right now.

I have Neek from the ZBB to thank for most of this. The part about bacteria consuming, using and then disposing of radioactive isotopes, and the parts describing how they are able to do it, were his ideas. I merely applied Endosymbiotic Theory to it and then constructed larger multicellular organisms with it. As implied, there will be many, many different kinds of these organisms. The largest of which will form an endosymbiotic relationship with sporophytic plants, much like lichens do with moss on Earth, and will play an important role in many of the stories I will set in my conworld. I will save that, and any further data on the new kingdom of organisms I came up with, for my conworld articles on this Wikia.

Something ironic about that second article on Chernobyl mushrooms is that the author of that article used the word "radiosynthesis"... I had come up with that same word around the time (maybe even before) I posted that thread on the ZBB about my fifth kingdom of like and Neek replied with all of that information. He will be definitely be listed as a contributor after that.

Both of those mushroom articles show that while we think we know everything there is to know about the natural world and/or how it works, something like glowing and "radiosynthetic" mushrooms are discovered and still manage to surprise us. This is good for conworlding because it still means that our imaginations still have lots of room in which to grow when creating conworlds that can be very realistic. There is an important part of scientific philosophy that says the scientist never really "knows" anything; it is possible for even our most basic theories to be corrected in time and practice. We just need to be willing to learn from them when they do.

Thanks for reading.