Archive for January 11th, 2013

January 11, 2013

The Fungus Among Us

by Melissa Harding


Lichens are inconspicuous organisms. These pieces of pale, calcified lace are content to sit quietly on tree trunks, tombstones, and rock ledges for decades without making much fuss; their only real threat in life is a heavy rain. Despite all that, there is much to like about lichens. For starters, they may hold the key to immortality. Scientists are finding that some organisms get stronger and larger as they age, rather than smaller and weaker. (For instance, the giant sequoia.) Lichens are just one example of this phenomenon in nature and some researchers are trying to figure out what that means for the rest of us. New York Times author Hillary Rosner explores this topic with her profile of Dr. Anne Pringle, a Harvard mycologist studying the aging process in lichens. Dr. Pringle believes that research on lichens may answer the question: Is immortality possible?

To begin with, lichens are not individuals, but rather a community of smaller organisms. Each lichen is composed of one main fungus, a group of algae and other, smaller fungi and bacteria. Since fungi are incapable of making their own food, they usually provide for themselves as parasites or decomposers. In lichen, the main fungus is essentially farming the algae for food. This means that lichens are composed of both plants and fungi, making them rather hard to classify.

Because lichens are a compound organism, reproduction can be tricky. To reproduce and expand their range, a lichen can either launch a single fungal spore that must then find a new algae to join with, or it can send out fingerlike projections called isidia, which contain both algae and fungi, to find a new home. The neat thing about lichens is that they will colonize areas that other organisms cannot. They grow on bare rock, desert sand, cleared soil, dead wood, animal bones, rusty metal, and living bark. With the right amounts of light, moisture and freedom from competition, lichens can grow anywhere. They can even survive extremes of heat, cold, and drought by hibernating. All in all, lichens are amazing organisms.

Perhaps few can appreciate them like Dr. Pringle. For eight years, she has been studying lichen formations in a Massachusetts cemetery, trying to figure out if they are deteriorating with the passage of time.  Biologists call this senescence, or declining with age.  Dr. Pringle is looking to see if the lichens are more likely to break apart over time and if their chemical or bacterial composition changes as they age, leaving them more vulnerable to pathogens.

Though Dr. Pringle is studying lichens, what she is really interested in are the fungi inside them. Scientists have long suspected that fungi don’t age, but there has been little research to back this up. A longstanding explanation for aging is that built-up genetic mutations are activated once fertility begins to taper off.  Another theory is that aging occurs because some traits that make us more reproductively successful may also be dangerous. For example, high testosterone increases fertility, but also is a known prostate cancer risk factor. Neither theory works here, since fungi reproduce asexually using spores. In fact, fungi reproduce more as they age, not less.

Dr. Pringle’s preliminary results show that as a lichen grows older and larger, it is less likely to die. The definition of aging changes from organism to organism. Death, as we know it now, is animal-centered. The rules for fungi, as well as the subjects of similar studies like the bristlecone pine and the wandering albatross, are something different.

To learn more about lichen and Dr. Pringle’s research, check out this article by Hillary Rosner in the New York Times.

The above photo was provided courtesy of Evan McGlinn of the New York Times.


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