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A useful principle in the story of life is that you should never underestimate algae or cyanobacteria. They’ll just always manage to surprise you, and more importantly, to remind you that everything you have comes down, eventually, to them.
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Stock video from:
https://www.gettyimages.com/detail/video/the-growing-lichens-on-the-tree-trunk-in-estonia-stock-footage/1414110263
https://www.gettyimages.com/detail/video/evernia-prunastri-lichen-on-a-tree-branch-stock-footage/1307151481
https://www.gettyimages.com/detail/video/female-three-toed-sloth-climbs-tree-with-baby-2-stock-footage/505038230
https://www.gettyimages.com/detail/video/cladonia-pyxidata-trumpetlinchen-in-montserrat-stock-footage/1302924185
https://www.gettyimages.com/detail/video/lichens-close-up-in-the-wood-stock-footage/1475326764
https://commons.wikimedia.org/wiki/File:Frank_Albert_Bernhardt.png
https://commons.wikimedia.org/wiki/File:Simon_Schwendener,_1899_-_Accademia_delle_Scienze_di_Torino_0155_B.jpg
SOURCES:
https://www.niehs.nih.gov/health/topics/agents/algal-blooms/index.cfm
https://www.livescience.com/54979-what-are-algae.html
https://royalsociety.org/news/2014/sloths-moths-mutualisms/
https://www.fs.usda.gov/wildflowers/beauty/lichens/habitat.shtml
https://www.fs.usda.gov/wildflowers/beauty/lichens/about.shtml
https://www.livescience.com/55008-lichens.html
https://ohioplants.org/lichen-biology/
https://journals.asm.org/doi/10.1128/microbiolspec.FUNK-0011-2016?url\_ver=Z39.88-2003&rfr\_id=ori:rid:crossref.org&rfr\_dat=cr\_pub%20%200pubmed
https://www.fs.usda.gov/wildflowers/beauty/lichens/biology.shtml
https://www.researchgate.net/publication/232679369\_Simon\_Schwendener\_1829-1919\_and\_the\_Dual\_Hypothesis\_of\_Lichens
https://www.nature.com/articles/nrmicro2010
https://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-022-01804-6
https://www.science.org/doi/10.1126/science.aaf8287
This video has been dubbed using an artificial voice via https://aloud.area120.google.com to increase accessibility. You can change the audio track language in the Settings menu.
This episode is sponsored by Squarespace. Go to Squarespace.com/microcosmos to save
10% off your first purchase of a website or domain. A useful principle in the story of life is
that you should never underestimate algae or cyanobacteria. They will always manage to surprise you,
and more importantly, to remind you that everything you have, ultimately comes down to them. Do you like oxygen? Well, take some time to thank a cyanobacterium. If their ancestors hadn’t gone a little
haywire with their
photosynthesis and set off the Great Oxidation Event billions of
years ago, we would not exist. But you don’t even have to look back into
history to see the influence of algae and cyanobacteria. Today, even algae of the smallest size have
a tremendous impact on our lives, both good and bad. On one hand, they translate sunlight into
food through photosynthesis. On the other hand, they bloom in waters and
release toxins that can wreak damage on the organisms around them. But the real reason you sh
ould never underestimate
algae or cyanobacteria is because at their core, they are organisms that seem to just
always find a way. They exist in super salty waters, in ponds,
in hot springs. Though, these are of course aquatic organisms, and
so you might think of their adaptations as restricted to watery environments. But what has made algae so capable of existing
beyond those boundaries is their willingness to use other organisms as a means to their
own survival. At times, their symbiotic relat
ionships sound
absurd, like the species that makes a home out of sloth fur. But our favorite example of the creativity
that algae and cyanobacteria approach their relationships with has to be lichen— that combination of fungus and algae, or fungus
and cyanobacteria, that attaches to trees and rocks and anything else that sits around
long enough. The concept of a lichen appears simple enough. There’s a fungus, which has an incredible
capacity for spreading and decomposing, but no means to make it
s own food. And there’s the algae or cyanobacteria,
fully capable of making their own food, but in need of some help getting around on land. The result is called a dual organism, made
up of the fungal mycobiont and the algal photobiont that takes on the spreading qualities of the
first, and the colors of the second. Fungi and algae can meet and work together
in ways that actually don’t result in a lichen. The distinct structure that we associate with
lichens comes down to the thallus, made up of
distinct layers that reveal the different
combinations of the organisms that make it. The thallus is what allows lichens to survive,
keeping the organism alive in dry conditions so it can tolerate extremes in humidity and
temperature. The shape is generally a function of the fungus,
which starts to weave its body into the appropriate layers as soon as it comes upon algae to team
up with. At the edge is the cortex, where fungal cells
are thicker and close in contact so they can form a protective
structure. And beneath, it keeps a more fibrous and loose
mass of hyphae, a scaffolding structure called the medulla that the photobionts layer themselves
on, dividing and creating their own algal layer that’s large and green and positioned
to access the sun. That layer of cells tells us a little bit more about
the organisms inside the lichen, though only under the right conditions. A dry lichen is typically gray. But with water, the fungal gray clears up,
revealing the color of the photobionts
inside the lichen. In the case of algae photobionts, you’ll
typically see a bright green color. But when there are cyanobacteria, the hues
vary from dark green to black. Now lichens have to actually stick to the
thing they are stuck to, and they have a few ways to anchor
themselves onto surfaces. Some have a structure called a holdfast that
extends as part of the thallus, a bit like a peg that is very good at holding on to things
like rock. Our lichen here though uses a different type of
struc
ture called rhizines. These are threads that come from the medulla
or lower cortex, creeping out from the lichen like roots, only they do not have any
capacity to draw in nutrients. They are just anchors. Now from our perspective right now, there’s
nothing controversial about this partnering of fungus and algae. We look in the lichen, we see signs of both
organisms, and we boil it down to a simple exchange of protection for food. This ancient relationship brought algae onto
land and into place
s so different from their watery origins. But our understanding of lichens as not just
one organism, but two is actually relatively recent, going back only to 1867, when a Swiss botanist
named Simon Schwendener presented his work at the Swiss Natural History Society. He’d been looking at lichen under the microscope,
just as we are now, when he considered the possibility that the mass of hyphae he was looking at
belonged to a fungus, wrapped around algae. His contemporary lichenologists did not
agree. Sure, Schwendener was just one of multiple
scientists who had noted a resemblance between the parts of lichen, and the bodies of fungi
and algae. But that was just a resemblance, it seemed
to the lichenologists at the time. In their defense, they did not know that
a dual organism could exists, They did not know that there was a symbiosis here How could they, when the word symbiosis
hadn’t been invented yet? Schwendener had more reasons than just appearances
though. One challenge that lich
enologists repeatedly
came across was that it was impossible to grow a new lichen from isolating either the
spores or the green cells growing within the lichen. But in 1877, a scientist named Albert Bernhard
Frank came up with the term “symbiosis.” The organism that inspired him to come up
with that word? Well of course., it was lichen. Frank was one of several biologists intrigued
by the possibility of Schwendener’s hypothesis, this idea that organisms could live together,
not just in an enviro
nment, but in one entity. Now with time, lichenologists came around, and
people only uncovered more examples and nuances around symbiosis. But that does not mean that we
actually understand lichen. They remain challenging to cultivate in a
lab, and we’re still understanding whether the symbiosis we’ve reduced to a simple
meeting of two organisms might actually more complex—whether it can involve other species
as well. Perhaps there’s a way to describe lichens
and the world inside of them that
we just don’t know yet, a word that, like symbiosis,
will reveal something new and remarkable to us about our world. The way we talk about science and knowledge
sometimes makes it feel like we’re done, that science is a static set of all of the facts
in the universe, because it is a lot easier to talk about the things
that we know than the things that we don’t. Of course it’s hard to talk about the things
that we don't know, because we don't know them. But our world is always there, containing
the information that we want in everyday occurrences that are sometimes hundreds
of millions of years old, we humans just have to figure out ways to
ask the questions that will actually give us answers. Thank you for coming on this journey with us as
we explore the unseen world that surrounds us. And thanks to Squarespace for sponsoring
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me to sit here at my desk and just be absolutely amazed and astounded by the completely invisible
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rd work
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Comments
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I used to teach the 5th-grade science class how Alice Algae met Freddie Fungus and they took a Lichen to each other. Thanks to recent studies I can't do that anymore without explaining what a throuple is
I actually read that recent research proves that a lichen always has one species of alga and two species of fungi. I was surprised nobody noticed in, you know, some 200 years, but I can't see it in these amazing images, either.
You know, I've really started to take a lichen to this channel. The writing is excellent and Hank is such a fungi!
I remember a chance encounter at a park with a fellow sitting on a rock looking over lichen. "Nice day, what are you looking at?" He told me about the symbiosis of lichen. I'd wondered since how integrated the cells were, thanks for showing such!
The level of quality this channel brings to every single video is just staggering.
"We don't know the tings we don't know". Equally profound and disturbing at the same time.
I remember when my local council in England proudly announced that someone had discovered a new type of lichen on a pavement. Sadly, during analysis it was noticed that the ‘lichen’ smelled faintly of mint and was actually chewing gum!
I’m just reading through the comments, and this channel has the sweetest fan base <3
maybe lichen is kind of like what life was on earth before it got more complex. Similar to how we eventually somehow captured mitochondria and integrated it, there was probably a time when our ancestor organisms were still just symbiotically coming togther.
Because they can both photosynthesize and break down minerals for food, lichens are one of the first lifeforms to recolonize after disasters like forest fires and volcanic eruptions. Scientists use the appearance of lichens as an indicator that an ecological area is recovering
If this is who I think it is narrating, thank you SO much for a) slowing the narration down and b) laying off all that redundant text. Much more relaxing this way…thanks again, excellent content as per usual.
I developed (ha!) a love affair with lichen when I got a camera with a microscope setting, that lets me take incredibly zoomed-in photos at extremely close range. I discovered an entire garden of lichen growing atop one of the old wooden fence posts of my mom's garden. The closer you get, the stranger and more beautiful they are. And of course, they also frequently play host to my OTHER favorite microorganism, the tardigrade!
Our perspective on the world is always limited by the language culture uses to describe it. It's like Godel's incompleteness theorem, there will always be true things about the world that stand apart from language, the framework we use to explain it to ourselves. It's the task of poets and visionaries to create new models, pushing the language of understanding right up to the boundary of what's speakable
your narritives and visuals give me a sense of peace while fueling my curiosity in a way no other channel has been able to achieve. i come here to relax and learn about little tiny guys, all while wearing my cozy microcosm crewneck which goes harder than any other sweater i own
Funny, I was thinking about lichen recently. Haven't washed my car in a while and there's something reddish growing on the roof. Was thinking of sending samples of it to James, if he's interested
What I don't yet understand is how a lichen is formed. Is it a fungus that meets an algae and in a kind off wedding for the lichen, or is the lichen something that produces spores that grow new lichen?
The photos were amazing! You should make posters of them!
I’m lichen this channel! So great. Keep up the good work!
I wonder to what extent lichens prepared the early Earth for green plants and animals, adding oxygen to the air and breaking down rocks.