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Hyphae Pseudohyphae Spores and the Real World of Molds and Yeasts

© Donald Reinhardt, January 24, 2013

They are all around us in the air, soil and water – some reside on our skin and inside our body – who are they? They are the fungi, the molds and yeasts and they are citizens of the microbial world. Learn more about molds and yeast and what they do.
Aspergillus mold, a fungus. Photo Credit: Centers for Disease Control, U.S.
Candida albicans, a yeast. Photo Credit: Centers for Disease Control, U.S.

Yeasts and Molds, What They Do and Their Characteristics and Features

Some fungi ferment sugar and other carbohydrates and produce flavorful byproducts. Baked breads and rolls are leavened (i.e., caused to rise from the flour mix) by the carbon dioxide (CO2) given off during the fermentation of the carbohydrates.  Saccharomyces, a yeast, changes sugar  into alcohol to help produce beers and wines. During fermentation lots of bubbles are seen in the vat or kettle containing these fermenting yeasts.

 Cheeses of various sorts are made by the Penicillium molds such as P. camembertii and P. roquefortii. The mushrooms, the polypores and the bracket fungi help degrade and decay leaves and wood into recyclable humus and new soil that contributes to the rich growth of plants and crops.

Yeast Features and Characteristics

Yeasts are usually described as eukaryotic cells (or simply – eukaryotes). Yeast usually form new cells by a process of budding (blastospore formation). Yeast cells grow to a certain size and produce these buds which grow larger and eventually separate away from the bud-generating cell and begin to form more yeast cells.

Yeast cell walls are composed of glucans and mannans, both are types of sugar polymers (monomers or unit sugars which chemically bonded together). Two of the most common yeasts are Saccharomyces and Candida. Candida albicans is a known yeast pathogen, an organism able to cause disease in an animal or plant.

Candida albicans can cause infections and disease of the skin, mucous membranes (thrush disease) and even, on occasion, may invade the bloodstream and other tissues to cause systemic damage to the liver, spleen, kidneys and lungs. Typical of many fungi which can become pathogenic (disease-causing) Candida and a few other fungi are known as opportunistic pathogens or adventitious  pathogens. This means the host animal or person is compromised and the compromised condition(s) permit the microbe to take advantage and begin to grow and multiply in the host. Compromised host conditions which promote  the invasion of host by adventitious or opportunistic pathogens  include diabetes, blood and other tissue and organ cancers, antibiotic use , corticosteroid, radiation and chemotherapy treatments. One case I recall particularly was a young girl who had leukemia which required chemotherapy and radiation treatments. During the course of her disease and treatment she developed a mold infection that invaded her lungs and contributed to her death.

Molds – the Filamentous Fungi –  and a Life of Hyphae and Spores

  These, too, are eukaryotic cells, with true nuclei bound by a double-membrane nuclear membrane as are the yeasts. Molds travel through the air as lofted spores and spread themselves everywhere. And where these spores find moisture and simple  food – leaves, wood, cardboard, paper or some simple starch or sugar they germinate and send out tubes seeking to absorb the nutrients they need to grow and multiply. Multiply they do, as they devour the foods they live upon and soon spores of their peculiar or particular type of these various  molds reproduce in abundance. Grow and spread as long as they are not dead, that’s what they do both day and night, and where moisture abounds they cause great fright. Why fright you say? Imagine your favorite book, a valuable painting, even leather boots and clothes covered with molds hyphae and spores even on moisture-laden doors and floors. So, if there ever is a flood in someone’s house or apartment these molds will soon make short work of that situation and begin to destroy many household goods unless they are quickly cleaned and dried.

Most molds help to recycle dead plants and animals in the natural environment. On occasion, molds, like some yeasts, are pathogenic (cause disease) or opportunistic pathogens that can cause skin, subcutaneous tissue, and blood and tissue-organ disease. Examples of these pathogens include the dermatophytes which cause skin, hair and nail disease because they enjoy breaking down the keratin protein found in these locations. Other pathogens include Histoplasma,  Blastomyces and Coccidioides  which can cause lung and disseminated disease.

Some Mold Definitions to See and Remember

Hyphae – fungus threads or mold filaments that are the vegetative, growing parts of the mold.
Pseudohyphae – hyphal-like strands that are really a series of blastospores which are elongate and look like true fungus threads. Pseudohyphae are common to Candida albicans and some other yeasts that are grown under certain conditions appropriate for the formation of pseudohyphae.

Asexual spores  – spores that are produced and formed on vegetative hyphae and which are produced only by simple mitosis. Examples: sporangiospores, blastospores, porospores,  conidia or condiospores.

Sexual spores – spores that result from the fusion of two different fungus cells and formed by a process called meiosis. There are: zygospores, ascospores and basidiospores.