Fungus Fact Friday

Category: Fungus Fact

#024: Fungi in the Production of Chocolate 1

Fungus Fact

#024: Fungi in the Production of Chocolate

Along with red roses and cheesy cards, chocolate is one of the common Valentine’s Day gifts. So on this day when heart-shaped boxes of chocolates are a common sight, I thought you might like to learn a little about how chocolate gets from the cocoa beans to the cloying boxes (be thankful I didn’t decide to discuss fungal diseases you can get from roses).  You probably already know that chocolate comes from the seeds of the cacao tree, Theobroma cacao.  The first way in which fungi allow for the production of chocolate is by helping the cacao tree to grow.  In order to get nutrients required for growth, all trees participate in mutualistic relationships with fungi called mycorrhizae.  There are a number of types of mycorrhizae, but Theobroma cacao only forms endomycorrhize.  In these mycorrhize, fungi in the phylum Glomeromycota penetrate the root cells of the tree and form specialized...

#023: Tremella fuciformis, the Snow Fungus 2

Fungus Fact

#023: Tremella fuciformis, the Snow Fungus

This beautiful jelly mushroom also goes by a variety of other common names, including: silver ear fungus, white ear fungus, and white jelly fungus. The fungus fruits from decaying wood and produces white, translucent mushrooms that have a gelatinous consistency.  Its name seems to come from its white color and roughly snowball-shaped fruiting bodies.  Although, if you ask me, its name was probably also inspired by its “graceful lobes,”* which look somewhat like large, squishy points on a snowflake.  The snow fungus’s range is tropical to subtropical, but it can apparently be found in the United States at least as far north as Indiana.   Despite its name, you will not find this mushroom poking out of snow-covered branches.  The mushroom prefers to fruit in the summer and fall, so if you want to see this fungus for yourself you’ll either have to wait half a year or visit the mushroom...

#022: Nematode-Trapping Fungi 1

Fungus Fact

#022: Nematode-Trapping Fungi

Fungi have developed a variety of ways to trap and kill nematodes. These include: adhesive branches, adhesive knobs, adhesive networks, non-constricting rings, and constricting rings.  None of these fungi use nematodes as a primary food source.  However, fungi sometimes need extra nutrients, especially nitrogen.  Forming traps is very energy-intensive, so they are only formed when nutrients are scarce and nematodes are present.  Fungi detect nematodes by “eavesdropping” on ascarosides, the chemicals that nematodes use to communicate with each other.  If you want to see these fungi in action and/or get a better understanding of nematophagous fungi, watch the YouTube video (in two parts) linked below*.  For your convenience, I have noted the time at which each type of trap is discussed in the video.

#018: Characteristics of the Phyla Blastocladiomycota and Neocallimastigomycota 1

Fungus Fact

#018: Characteristics of the Phyla Blastocladiomycota and Neocallimastigomycota

These two groups of fungi were recently taken out of the Chytridiomycota and elevated to the rank of phylum. Not surprisingly, both of these phyla produce motile spores (zoospores).  The blastocladiomycota inhabit fresh water and soil and fill similar ecological roles to the core chytrids.  Many of the blastocladiomycota are pathogens of small, aquatic animals (such as nematodes or water bears), algae, or semi-aquatic plants.  The genus Allomyces contains saprobic species often used in experiments.  In Allomyces the female gametes secrete the pheromone sirenin to attract the male gametes.  The main difference between the blastocladiomycota and the chytridiomycota is that the blastocladiomycota produce an extensive mycelium.  Furthermore, only certain cells at the tips of the hyphae produce sexual (male and female, haploid) or asexual (diploid) zoospores.  In the core chytrids, the entire thallus is used to produce zoospores.

#017: Characteristics of Phylum Microspora 1

Fungus Fact

#017: Characteristics of Phylum Microspora

Phylum microspora (not to be confused with the green algae genus Microspora) contains some of the most unusual fungi: the microsporidia. There are over 1200 described species in this phylum (and that is only a fraction of their biodiversity), divided into about 150 genera (plural of genus).  These organisms were originally thought to be protozoans, but recent DNA studies have demonstrated that they belong with the fungi.  The microsporidia are all obligate parasites of animals and have an extremely reduced cell structure.  They do not have mitochondria, so they can only grow and reproduce within the cells of their host.  Their very resistant spores persist in the environment for a long time and allow them to spread from one animal to another.  The spores are 1 to 40 micrometers long, making them the smallest eukaryotes.  The spores are rougly oval and have a cell wall made of chitin that is...

#016: Characteristics of the Defunct Phylum Zygomycota 0

Fungus Fact

#016: Characteristics of the Defunct Phylum Zygomycota

It has recently been demonstrated that the four subphyla historically classified as zygomycota do not make up a monophyletic group. As a result, the phylum zygomycota is no longer used. However, it has not yet been replaced by other phyla. The terms “zygomycota” and “zygomycetes” are therefore only used informally to reference this diverse group of fungi. The distinctive characteristic of the zygomycetes is their method of sexual reproduction (if a sexual stage exists). Their hyphae are almost always haploid. When two compatible (and haploid) hyphae meet they form gametangia, which fuse and become diploid. However, the diploid hypha is immediately isolated from the rest of the fungus. This isolated hypha then undergoes meiosis and develops into one zygospore. The zygospore is usually thick-walled and undergoes an obligatory period of dormancy before it germinates. This helps the spore survive for a long time in adverse conditions. Zygos also tend to...

#014: Characteristics of Phylum Chytridiomycota 1

Fungus Fact

#014: Characteristics of Phylum Chytridiomycota

Phylum chytridiomycota is the oldest phylum of fungi, with a fossil record dating back to the Vendian period (around 500 million years ago). It is no surprise, then, that chytrids are the simplest fungi.  Hyphae produced by chytrids can be unicellular, diminutive rhizoids or multicellular and as large as those produced by species in the other fungal phyla.  Chytrids are unique among the fungi in that they produce motile spores.  Each spore is equipped with one whiplash flagellum at its posterior.  Other fungus-like organisms which produce motile spores (often with multiple flagella) but have cellulose cell walls are no longer classified as fungi (chytrids, like all other fungi, have chitin in their cell walls).  Asexual zoospores are formed in a zoosporangium and are released through a pore.  The simplest chytrids form a very small network of rhizoids and produce only one zoosporangium per thallus.  However, more complex chytrids may form...

#012: Characteristics of Phylum Ascomycota 16

Fungus Fact

#012: Characteristics of Phylum Ascomycota

Phylum Ascomycota includes about 75% of described fungal species.*  It includes the baker’s yeast, Saccharomyces ceriviciae, scientifically important fungi such as Neurospora crassa and Penicillium chrysogenum, a number of desirable edible mushrooms, most notably morels and truffles, most lichenized fungi, and many important plant pathogens, such as the causal agent of chestnut blight.  As you can tell from this list, the ascomycetes have a variety of life history strategies and ecological roles.  Many ascomycetes grow as hyphae, others grow as yeasts, and some can even switch between the two.  Some ascomycota only reproduce sexually, others only reproduce asexually, and many do both.  Ascomycetes can be saprophytic (they decompose non-living matter), parasitic (on plants, bugs, humans, etc.), or mutualistic (with algae, plants, or even beetles).  Ascomycota have provided us with penicillin and have helped scientists understand the cell cycle, meiosis, and heredity.  Despite this diversity, Ascomycota is a monophyletic group (it...

#010: Fungal Fossils 0

Fungus Fact

#010: Fungal Fossils

It may surprise you to learn that fungi are reasonably well represented in the fossil record. Most of these fossil fungi are microscopic and lack reproductive structures. Additionally, it is often difficult to infer their ecology, making positive identification difficult, if not impossible.  Fossil fungi are often found inside fossilized plant tissue.  This includes fossils of mycorrhizae, plant pathogens, and wood decomposers.  Many of these finds come from Rhynie Chert in Scotland, which dates to the Devonian period (around 400 million years ago, characterized by small land plants and the first forests).  This is around the same time of the first fossilized land plants.  The fact that mycorrhizae were already well-established by this time suggests that fungi were instrumental in helping plants colonize the land.  The best-preserved fossil fungi are found in amber, often growing on insects.  A mosquito trapped in Baltic amber (from the Eocene period, around 47 million...

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Fungus Fact

#009: Overview of the Fungal Life Cycle

Filamentous fungi begin their lives as sexual spores. Each spore has a haploid (only one copy of each chromosome) nucleus, which is designated “n.” When the spore lands in a favorable environment, it germinates and produces a mycelium. There are two ways that this mycelium can grow vegetatively: through growth of the mycelium or through asexual reproduction. The fungus can produce asexual mitospores (n) which are dispersed and grow a new mycelium that is genetically identical to the parent. When this mycelium encounters another fungus with a compatible mating type they fuse together (plasmogamy). However, their nuclei remain separate and the cells become dikaryotic (meaning “two nuclei,” designated “n+n”). This gives rise to a dikaryotic mycelium. In ascomycetes and some other fungi, the dikaryotic mycelium only results in the production of fruiting bodies. In basidiomycetes, the dikaryotic mycelium grows vegetatively and produces fruiting bodies. Some basidiomycetes form clamp connections to...