Let's visit the Lichens: Microbes With A View! Ms. Myco Rhiza
Updated: Jun 5, 2021
Good morning precious littles! Today we are visiting the mountains! Perched on ledges with a fabulous view of NH's White Mountain Presidential Range, microbes cling to every surface. Those that choose to cling to the cliffs and rock surfaces enjoy awesome views all the time! The giants just tromp right by in an activity they call hiking, huffing, and puffing to try and catch spectacular views from the summits. If they only knew what was going on all around them at the microscopic level!
As you've been learning, we microbes are everywhere, even the mountains! Microbes can be found in many shapes and colors on the trees, on the rocks, on signs, everywhere! Even the giants, who normally need help seeing microbes, can see them if they look around.
Let's talk about some of the microbes that work together so well that they grow large enough to be seen by the giant kind without even needing a microscope, lichens! It’s pronounced ligh-ken (not lee-chen or ligh-chen). They grow in all kinds of shapes and colors.
Lichen is very common and grows all over the world, in just about every habitat and climate. It is estimated that lichens cover 6-8% of the earth's land surface! There are approximately 3,600 different species in North America - (20,000 worldwide) and we probably have not yet found them all! You may think that it is a plant because it’s often green and grows all over, but you would be wrong! They don't have roots to absorb water and nutrients like plants. However, like plants, Lichens (at least part of it) do use photosynthesis to create nutrients. They are also important because they are part of the ecosystem turning pollutants into O2 and nutrients! They are an important food source for deer and other animals and provide building materials for nests. However, Lichen isn’t really a thing, it’s actually two (or more) organisms living symbiotically.
Let's talk about symbiosis for a moment. When organisms share the same space, they will often enter into some type of relationship/interaction with one another. This interaction can be categorized into the 5 main types of symbiosis: Parasitic (Zombie Ants - yikes!), Predatory, Competitive, Commensal, and my favorite Mutualistic!
The first and more dominant organism in this symbiotic relationship is fungi (the mycobiont), and it is what provides the structure (thallus) for the lichen. Fungi are eukaryotes, organisms that have a nucleus, which includes all plants, animals, protozoa, and fungi. The kingdom of fungi includes organisms such as yeasts, molds, and mushrooms (which are fundamentally different from plants and animals) Want to eat some fungi salad, popcorn, or drink some mushroom coffee?).
Lichens are comprised of layers:
Cortex - a layer of densely packed fungal filaments that protects from sun and predators. In some Lichens (see below), sometimes there is an upper and a lower cortex.
Algal Layer - where the algal cells are embedded in the fungal hyphae (which are less densely packed, allowing for air circulation for photosynthesis to occur)
Medulla - a loosely arranged later of interfaced hyphae with a cottony appearance.
Basal Attachment - method of attachment to their substrate. Different types of lichens use different methods of attachment (see below).
Note: A few lichens don't have this structure and are more like jelly, everything mixed in a gelatinous blob - how fun!
The fungi give the lichen the majority of its characteristics (shape, growth, and movement). Hyphae are the tubular projections of multicellular fungi that form a filamentous network (mycelium). Fungal hyphae release digestive enzymes to absorb nutrients from food sources. They can't produce nutrients though, and that’s where the symbiotic partnership comes in, with algae or cyanobacteria (the photobiont).
While the fungus protects and houses it, algae or bacteria provide energy and nutrients for the fungus so it can grow. Pop Quiz! What type of Symbiosis is going on here? (answer below). Algae are in another kingdom (Protista) separate from plants and fungi. There are several types of algae: green, brown, red, gold. They can survive in saltwater and freshwater on their own, but when part of a lichen relationship, they can survive just about anywhere! Although cyanobacteria are called blue-green algae, they are actually bacteria and are part of the bacteria kingdom, Monera. The "blue" in the common name refers to the fact that they need to live in water, and "green algae" refers to their photosynthetic abilities, like green algae.
Many lichens will have multiple algae or bacteria contributing to the overall hue of the lichen. The shape and texture of the Lichen are determined by the fungi housing the algae. There are no roots or vascular systems like we see in the forest plants and they don't seem susceptible to weather and wear. The variety of combinations certainly make lichens beautiful in their own way. There are several main growth types of Lichen:
Crustose - the hyphae of the fungi are tight and form a crustlike body on the surface of rocks, trees, ships, etc. There's the cortex, which is the upper layer, which is usually pigmented, giving it color. The algal layer lies beneath, which is, of course where the algae live and the medulla layer fastens the lichen to whatever it is growing on (there's no lower cortex). These are flat against the surface and can withstand weather and giants stepping and sitting on it with no harm!
Foliose - these have two easily distinguished sides and are the structure is flattened layers of leaf-like tissue. The hyphae on the lower cortex attach themselves to surfaces with small root-like structures called rhizines.
Fruticose - these look a bit like coral or bushes and generally attach themselves to surfaces with a basal attachment called a holdfast. The algal body grows around the circumference.
There are other types too, but these are enough to get us started!
Pop Quiz time!
There is a lot more to lichens, but hopefully, you have enough info to start noticing them in your travels. Until next time class!
Lichen is formed by a mutualistic symbiosis between fungi and alga.
Fruticose lichen growing with some actual moss (a plant)
It looks like she's found some leafy foliose lichen on that tree!
It is! Native Americans, soldiers, and lost starving wanderers have eaten it, but it doesn't have much nutritional value and wouldn't taste great.
Crustose - what a view! If only they had eyes!
Yes! I can see fruticose and foliose!
Comment below if you have some cool lichen pics!