Fungus Fact Friday

Author: Thomas Roehl

#006: Zombie Ants 4

Fungus Fact

#006: Zombie Ants

The parasitic fungus Ophiocordyceps unilateralis infects rainforest ants, turning them into “zombie ants.”  The fungus takes over the ants’ minds and directs the ants to die in the most advantageous spot for the fungus.  Although this ant/fungus interaction has been known since 1859, it only recently (within the past 5 years) fell under the public eye after a study examined some of the specifics of this interaction.  The story starts when a fungal spore lands on the exoskeleton of an unsuspecting ant.  The spore germinates and forms an infection structure called an appressorium.  This structure is capable of producing enormous pressure (fungal plant pathogens have been known to produce pressures equal to the pressure inside the wheel of a 747) which allows the fungus to penetrate the ant’s exoskeleton.  Then, the real fun begins.  Ant colonies exhibit a behavior known as “social immunity,” where diseased individuals are forcibly removed from...

#005: Xylaria polymorpha, Dead Man’s Fingers [Archived] 2

Archived

#005: Xylaria polymorpha, Dead Man’s Fingers [Archived]

Note: this is an archived post. You can read the updated version here. October is Creepy Fungus Month on Fungus Fact Friday! To start this month I have chosen to highlight Xylaria polymorpha–Dead Man’s Fingers. When you look at this fungus’ fruiting bodies in the summer or fall it is easy to see how it got its common name.  The mushrooms are more or less straight, though often bent or warped.  Their exterior is black, wrinkled, and bumpy and becomes cracked with age.  The individual mushrooms often grow close together and may become fused at the bottom, forming a “hand” with several “fingers.”  X. polymorpha is a wood decomposer, but can often appear to grow from the ground when decomposing buried wood.  Thus, this mushroom often resembles a burnt, dead hand reaching out of the ground to grab unwitting passers-by and drag them down into the depths of the earth. ...

#004: Fungal Hyphae Are Not Made Up of Traditional Cells 3

Fungus Fact

#004: Fungal Hyphae Are Not Made Up of Traditional Cells

The mycelium of a fungus is made up of one continuous cytoplasm and is thus said to be coenocytic.  Most hyphae have structures called septa that divide the hyphae into cells.  Each septum has a central pore (or multiple micropores) which allows it to regulate movement of nuclei and other organelles and to allow nutrients and resources to be quickly moved around.  There are a few levels of complexity of septa.  The least complex level has no septa, and the nuclei are free to move around the hyphae.  In this case there are many nuclei in each hyphae and the hyphae are said to be polykaryotic (plant and animal cells are usually monokaryotic*).  In mated fungi, this allows for an interesting situation where you can think about populations of nuclei within an individual.  Other hyphae are septate but have a large pore at the center of each septum.  This pore...

#003: Yeast vs. Hyphae 5

Fungus Fact

#003: Yeast vs. Hyphae

There are two major fungal growth modes: yeast and hyphae.  Yeast are single-celled organisms.  Hyphae are multicellular,*branching tubes that form mycelial networks.  Although “yeast” is commonly used to refer to Saccharomyces cerevisiae, yeast are a very diverse group.  Actually, they are not even a single group: yeast are placed into both Ascomycota and Basidiomycota.  These are the same two phyla that contain mushrooms, which exhibit hyphal growth.  Yeast grow by increasing the volume of the cell and then dividing through mitosis.  This mitosis can follow either a fission or budding pattern.  In fission, the cell divides in half and the cytoplasm is split equally.  In budding, a small bud forms off of the cell.  The nuclei replicate and half of them move into the bud.  The bud grows in size and eventually separates.  At this point the bud is still smaller and the cytoplasm is not divided evenly.  Under certain...

#002: Agaricus bisporus 13

Fungus Fact

#002: Agaricus bisporus

Agaricus bisporus accounts for about 90% of mushroom production in the United States, and 40% worldwide.  bisporus is the classic grocery store mushroom.  It goes by a variety of common names, including: “button mushroom,” “white mushroom,” “crimini,” and “portabella” (there are a variety of spellings for portabella).  That’s right, all of these are actually the same mushroom!  Crimini and portabella mushrooms come from a more flavorful brown strain of A. bisporus.  Portabellas are exactly the same strain as criminis but the mushrooms have been allowed to mature.  A. bisporus is commercially cultivated in large indoor facilities.  It is a secondary decomposer, so the substrate it is to be grown on needs to be composted first and then purified of the primary decomposers.  The growers then purchase “spawn” to inoculate the substrate with A. bisporus.  The spawn consists of A.bisporus mycelium growing on cereal grain.  The mycelium will grow through the...

#001: Armillaria ostoyae, the Humongous Fungus 3

Fungus Fact

#001: Armillaria ostoyae, the Humongous Fungus

Welcome to Fungus Fact Friday! To start off this exciting new series I have chosen a simple yet amazing fungus fact: the largest known living, single organism on the planet is a fungus; Armillaria ostoyae to be specific!  The Armillaria genus contains good edibles and includes species commonly known as “honey mushrooms” or “shoestring fungi.”  The second name comes from the thick, black rhizomorphs that connect various areas of the fungus together.  These rhizomorphs form under the bark of trees that the fungus attacks parasitically and extend through the soil from tree to tree.  This infection causes the trees to die back, which makes the 2,385 acre area the fungus has colonized visible from the air.  DNA tests taken from ostoyae samples all around the infected area showed that this was one individual (for the moment I have put aside the “what is an individual?” debate, a very confusing subject...