Lichen Revolution

lichen_davis-mtns

Lichen on Rocky Ground, Davis Mountains

Back in 2009 I wrote a little article about lichen, those symbiotic organisms that have intrigued biologists for so long. At the time I wrote the piece, it was generally believed that lichen were usually a partnership of two species, a fungus and a bacteria, though some were known to have more than one bacteria in the group. It turns out that this is not true.

You can easily see how this theory came to be so widely accepted by simply looking at a slice of lichen under a microscope. Here you can see the different organisms that cooperate to create a lichen.

lichen-layers

Photo from Microscopy-uk.org

In this image you can see the photosynthesizing bacteria arranged just beneath the surface to catch the light, while the supporting fungus, here stained blue, lives below.

The species pairings are usually quite specific; for each fungus there is one bacteria that will join with it to create a lichen. It would seem, therefore, that each unique pairing would produce a specific lichen. But this is not always the case – apparently different lichen are sometimes made of the same symbiotes. Moreover lichenologists who have attempted to combine two species known to coexist in real lichen, have not been able to graft the two species together to create a viable lichen. Why?

The situation intrigued Dr. Tony Spiribille who has been studying lichen for over 15 years. He was particularly interested in two North American lichen which contain the same symbiotes, but which are different in several ways. Bryoria fremontii, sometimes called “Tree Hair Lichen” is a dull brown and looks like thick hair.

wilabig

Byoria fremontii

Bryoria tortuosa is yellow or greenish yellow and has finer threads.

bryotort

Bryoria fremontii is is edible – Bryoria tortuosa is poisonous.

Thinking that these two lichen must be different in some way, Dr. Spiribille sequenced their DNA. But DNA from the two lichen appeared to be genetically indistinguishable! Clearly a closer look was called for.

Working with another group at the University of Montana, Dr. Spiribille used advanced sequencing technology to run RNA “deep scans” of the two lichen. Surprisingly, the RNA scan revealed the presence of a third species that was present in both lichens. Believing that his samples had somehow been contaminated he repeated the experiment, several times, but the third species always showed up. It is a species of Basidiomycetes fungus, previously unknown. He found that the Basidiomycetes fungus produces the substance that makes B. tormentosa so toxic. B. fremontii has the fungus, but very little of it, so it is safe to eat.

Dr. Spiribille then asked other lichenologists around the world to look for the Basidiomycetes fungus. Amazingly, they found it in every lichen they examined i It has now been found on every continent on earth. Moreover molecular evidence indicates that it has been part of lichen symbioses from the start of this partner’s evolution. Unnoticed for almost 150 years, this single species of fungus appears to play an important role in the lives of lichen everywhere. Dr. Spiribille’s remarkable discovery now points the way to a whole new area of research, one which we didn’t imagine just a few years ago.

Advertisements

About aneyefortexas

Retired writer/teacher/photographer, now photographing the Chihuahuan Desert at the Big Bend Ranch State Park, Texas.
This entry was posted in General Topics, Plants. Bookmark the permalink.

10 Responses to Lichen Revolution

  1. bluebrightly says:

    Amazing! I live in the Pacific northwest, where lichens are everywhere. And fungi. And get-togethers! (Seriously, it’s great when a blog post sparks such good comments – thanks!).

  2. Mary J. Matthews says:

    In 1969 I was a freshman in a small Missouri high school. I was fascinated by the flora and fauna on our 65-acre farm, and for my science project I studied and collected lichens. After 46 years, the name of the most splendid, spectacular specimen still comes to the surface: “Scarlet Crested Cladonia!” Thank you for studying and working to preserve lichens on our world.

  3. Mike Mecke says:

    Source: Aneyefortexas – a blog that someone in West Texas started sending to me once in a while since living out there – very good, some very interesting articles and info. mike Aurel says: September 11, 2014 at 10:56 pm I usually don’t like blogs. This is an exception. You are providing a service and a resource I have not been able to find elsewhere — a well written explanation of the flora and fauna of West Texas, especially of the desert, backed up with great photos. Much appreciated.

    ****************************************************************************************************

  4. Priscilla Rutherford says:

    so good to hear from this site I had forgotten about it

  5. Deborah Douglas, M.D. says:

    Gary, I loved this write-up! Below is a recent article from Science Daily. I do love lichens!

    We’ll be arriving in Terlingua late on August 6th, staying til the morning of the 8th. We hope to see y’all then.

    Be on the lookout for bumblebees at the Warnock Center and environs; Tom and I are oh-fficial agents of a TPWD study (led by Dr. Jessica Beckham) with the task of collecting bumblebees in designated areas of West Texas. Love,Deborah

    Yeast emerges as hidden third partner in lichen symbiosis – Date: – July 21, 2016 – Source: – Purdue University – Summary: – For nearly 150 years, lichens have been the model organisms of symbiosis. Now researchers have uncovered an unexpected third partner embedded in the lichen cortex or ‘skin’ — yeast. Lichen.Credit: © varbenov / Fotolia Lichen.Credit: © varbenov / FotoliaClose For nearly 150 years, lichens have been the model organisms of symbiosis. Now researchers have uncovered an unexpected third partner embedded in the lichen cortex or “skin” — yeast.Since 1867, scientists have recognized the fundamental partnership that produces lichens: A fungus joins with an alga or cyanobacteria in a relationship that benefits both individuals. In a study led by the University of Montana and co-authored by Purdue mycologist M. Catherine Aime, researchers show that lichens across six continents also contain basidiomycete yeasts, single-celled fungi that likely produce chemicals that help lichens ward off predators and repel microbes.The finding could explain why many genetically similar lichens present wildly different physical features and why scientists have been unable to synthesize lichens in the laboratory, even when combining species that partner successfully in nature.”This discovery overturns our longstanding assumptions about the best-studied symbiotic relationship on the planet,” said Aime, professor of botany and plant pathology. “These yeasts comprise a whole lineage that no one knew existed, and yet they are in a variety of lichens on every continent as a third symbiotic partner. This is an excellent example of how things can be hidden right under our eyes and why it is crucial that we keep studying the microbial world.”Based on his study of lichens, Swiss botanist Simon Schwendener was the first scientist to propose that some organisms are not autonomous individuals but combinations of unrelated species that work together. He observed that lichens are the result of collaboration between a single fungus and a photosynthetic partner — either an alga or cyanobacterium. The alga or cyanobacterium produces food by converting energy from the sun and carbon dioxide into sugars. The fungus, in turn, forms the main structure of the lichen and offers its photosynthesizing partner protection from the environment.This cross-kingdom combination of strengths and abilities has allowed lichens to thrive on a variety of surfaces and in almost every habitat on the planet, ranging from the Arctic to deserts. They come in myriad shapes, colors and forms and produce a rich variety of secondary metabolites. Lichens were also some of the first land-dwelling organisms, suggesting that a communal effort helped life make the ocean-to-land leap.The discovery that specific yeasts act as third symbiotic partners in lichens began with an investigation into why two lichen species seemed genetically identical but had distinctive attributes. The lichen Bryoria tortuosa is yellow and produces a toxic substance known as vulpinic acid while B. fremontii — made up of the same fungus and alga — is dark brown and produces no such acid. An analysis of gene expression of the known fungal partner in the two species showed no differences.But when the team broadened the data search to include all fungi, they found indications that genes were being expressed differently — unexpectedly, by a fungus that appeared to belong to the Basidiomycota, a completely different phylum than the known fungal partner. These data suggested the presence of a second fungal partner, an undescribed species of yeast in a poorly studied class of early-evolving basidiomycetes.Toby Spribille, first author of the study and postdoctoral researcher at Montana, said he was initially skeptical of the results.”It took a long time to convince myself that I wasn’t dealing with a contamination,” he said.But once the researchers began looking for traces of similar yeasts in other lichens, they found related lineages in 52 genera of lichens worldwide and molecular evidence that indicates a long, shared evolutionary history between the symbiotic partners.”There is a long, venerable history of scientists and natural historians who have peered at lichens through microscopes since the 1800s,” said Spribille, also a postdoctoral researcher at the University of Graz. “The yeasts were always there, and somehow we got to crack it open. It gives me goose bumps.”The high amounts of yeast in B. tortuosa enable the lichen to produce the acid that helps defend it against invasion from other microbes. Aime’s work with related yeasts points to similar beneficial roles in plants, but basidiomycete yeasts are still understudied, she said.”We have barely touched the tip of the iceberg in understanding the importance and ubiquity of microbes in a variety of biological systems,” she said. Story Source:The above post is reprinted from materials provided by Purdue University. Note: Materials may be edited for content and length. Journal Reference: – T. Spribille et al. Basidiomycete yeasts in the cortex of ascomycete macrolichens. Science, 2016 DOI: 10.1126/science.aaf8287 Cite This Page: – MLA – APA – Chicago Purdue University. “Yeast emerges as hidden third partner in lichen symbiosis.” ScienceDaily. ScienceDaily, 21 July 2016. .Purdue University. (2016, July 21). Yeast emerges as hidden third partner in lichen symbiosis. ScienceDaily. Retrieved July 27, 2016 from http://www.sciencedaily.com/releases/2016/07/160721151213.htmPurdue University. “Yeast emerges as hidden third partner in lichen symbiosis.” ScienceDaily. http://www.sciencedaily.com/releases/2016/07/160721151213.htm (accessed July 27, 2016).   Deborah Douglas, M.D. (210) 845-3077 

    On Wednesday, July 27, 2016 5:46 PM, aneyefortexas wrote:

    #yiv1297075281 a:hover {color:red;}#yiv1297075281 a {text-decoration:none;color:#0088cc;}#yiv1297075281 a.yiv1297075281primaryactionlink:link, #yiv1297075281 a.yiv1297075281primaryactionlink:visited {background-color:#2585B2;color:#fff;}#yiv1297075281 a.yiv1297075281primaryactionlink:hover, #yiv1297075281 a.yiv1297075281primaryactionlink:active {background-color:#11729E;color:#fff;}#yiv1297075281 WordPress.com | aneyefortexas posted: “Back in 2009 I wrote a little article about lichen, those symbiotic organisms that have intrigued biologists for so long. At the time I wrote the piece, it was generally believed that lichen were usually a partnership of two species, a fungus and a bacte” | |

  6. Peter Harris says:

    Very cool work–and a very interesting discovery. Thanks for sharing it.

    Peter

  7. jesusan says:

    This is fascinating. I thought I remembered that lichens were made up of a fungus and an alga. Never heard about bacteria being part of them. Obviously a lot of new info has been gained in the 50 years since I graduated from college… Thanks for a great lesson.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s