Microscopic Views of Yeasts

I borrowed the following from a mycology website in England and will make appropriate comments (in green) throughout. I will also boldface some of their black text so you can grasp the important parts without changing the actual words they used.

Yeasts are fungi that grow as single cells, producing daughter cells either by budding (the budding yeasts) or by binary fission (the fission yeasts). They differ from most fungi, which grow as thread-like hyphae (definition: any of the threadlike filaments forming the mycelium of a fungus). But this distinction is not a fundamental one, because some fungi can alternate between a yeast phase and a hyphal phase(1), depending on environmental conditions. Such fungi are termed dimorphic (with two shapes) and they include several that cause disease of humans.

Note 1: This is important in human physiology. If a fungus can alternate between these states, it is capable of self-propulsion (travel) throughout your system, then embedding itself to grow (colonize). Then pieces can break away, alternate forms, travel, then embed and colonize. In cancer terminology, this would be called metastasizing, although at this point we wouldn’t use that word because, as yet, the invading fungi have not altered your DNA to cause uncontrolled cellular growth. Right now, these yeasts are merely feeding on your body’s available nutrients and spreading their own cells in an attempt to become the dominant parasite.

Here we consider several examples of yeasts and dimorphic fungi:

• the common baker’s yeast, Saccharomyces cerevisiae
• the genus Cryptococcus, which includes C. neoformans, a pathogen of humans
• the dimorphic fungus Candida albicans which can be a significant pathogen of humans
• some of the common leaf surface yeasts.

Yeasts grow typically in moist environments where there is a plentiful supply of simple, soluble nutrients such as sugars and amino acids(2). For this reason they are common on leaf and fruit surfaces, on roots and in various types of food. With few exceptions, they are unable to degrade polymers, such as starch and cellulose, which are used by many hyphal fungi.(3)

Note 2: Where in your body would you expect to find those conditions? Start with your intestines, where several times a day you feed them exactly what they need for growth. Then they spread out and can obtain their needs just about anywhere in your body.

Note 3: Hyphal is merely the adjective form of hyphae, so to say a normal yeast cannot degrade polymers, but to say the hyphal types can, implies that when they switch forms, they can consume just about anything.

Saccharomyces cerevisiae (Figure A) is the budding yeast (often called baker’s yeast) used for bread-making, where the carbon dioxide produced by growth in the dough causes the bread to rise. Essentially similar yeasts, but now given different species names, are used for production of beers, wines, and other alcoholic drinks (usually called brewer’s yeast). This phase-contrast micrograph shows cells in various stages of budding. The buds are small at first, but enlarge progressively and eventually separate from the mother cell by formation of a septum (cross wall).

Few of the cellular organelles (definition: a specialized part of a cell; analogous to an organ) can be seen by light microscopy, unless they are stained specifically. The only conspicuous organelle seen in Fig. A is the large central vacuole (definition: a tiny cavity filled with fluid in the cytoplasm of a cell), which contributes to cell expansion. S. cerevisiae is a member of the fungal group Ascomycota (the ascus-forming fungi; definition: ascus is a saclike structure in which ascospores are formed through sexual reproduction of ascomycetes).

Cryptococcus albidus (Figure B) is another budding yeast, shown here by phase-contrast microscopy, but also with negative staining (the cells are suspended in India ink). Various stages of bud development are seen. The cells are surrounded by a rigid polysaccharide capsule, typical of the genus Cryptococcus, and seen as distinct haloes where the India ink particles have been excluded. (Unless you are specifically looking for fungi in your microscope, when these appear mixed in with an unstained blood sample, the average technician or doctor will simply assume these are also red blood cells and never know you have a systemic yeast infection.)

Cryptococcus species are common on leaf surfaces. But the most important species from the human standpoint is C. neoformans, a significant pathogen of immunocompromised people, causing the disease termed cryptococcosis. This disease occurs in about 7-8% of AIDS patients in the USA, and a slightly smaller percentage (3-6%) in western Europe. The capsule is a significant virulence determinant of C. neoformans because it helps to prevent the cells from being recognized and engulfed by white blood cells. Additionally, C. neoformans is unique among Cryptococcus species in producing a phenoloxidase. This enzyme acts on phenolic compounds to produce melanin, which might help to protect the cells against the antimicrobial effects of oxidants in host tissues.

C. neoformans grows commonly on old “weathered” bird droppings in cities, but does not compete well with bacteria in wet droppings. It infects through the lungs, where it causes a mild or chronic, persistent pneumonia, depending on the person’s degree of immunity. Random testing of people for skin reactions to C. neoformans antigens in Britain, Australia, and the USA indicates that many people have unknowingly been exposed to the fungus with no serious effect. However, in a small proportion of the population, the fungus can disseminate “silently” in the central nervous system, causing fatality.

For many years it was assumed that yeast cells inhaled in dried, powdered bird droppings were the source of lung infection. But a sexual stage of the fungus has now been discovered in laboratory culture; it is typical of the fungal group Basidiomycota (which includes the mushroom fungi) but is microscopic, and it leads to the release of small (about 3 micrometers) airborne basidiospores. These are the ideal size for deposition in the lungs (see  http://helios.bto.ed.ac.uk/bto/microbes/Top). They are thought to be the main means of infection, but their environmental source is unknown – perhaps a yeast stage growing on vegetation.

Candida albicans (Figures C, D) is a dimorphic fungus that grows at 37^oC. Its normal habitat is the mucosal membranes of humans and other warm-blooded animals, where it grows as a yeast (Fig. C) and causes little or no damage. In fact, it can be isolated from the mucosa of up to 50% of humans - from the mouth, the gut, the vagina or, less often, from the surface of the skin.

In some circumstances, however, the same strains of C. albicans that grow as harmless commensals (definition: either of two different animal or plant species living in close association but not interdependent) can become pathogenic, invading the mucosa and causing significant damage. This usually happens when a variety of predisposing factors cause the yeast population to multiply, escaping the normal competition from resident bacteria that keep the yeast population in check. Then the yeast cells sprout a hyphal outgrowth (Fig. D), which locally penetrates the mucosal membrane, causing irritation and shedding of the tissues.

One of the best examples of this is the disease termed thrush - a white speckling of the tongue and the back of the throat, resembling the speckling on the bird’s chest. This is common in newborn babies, perhaps resulting from passage through an infected birth canal. It is also common in AIDS patients and people who have had a prolonged course of antibacterial therapy, reducing the normal resident bacterial population. (4)

Note 4: Damn, a doctor is in agreement here that antibiotics, in reducing the normal resident bacterial population in your body, leave you wide open to other invaders to cause you problems.

C. albicans also causes vaginitis - inflammation and invasion of the vaginal mucosa, especially during the third trimester of pregnancy and in women who take the pill. The predisposing factors seem to be hormonal, associated with changes in the balance of cell types in the lining epithelium (definition: membranous tissue covering internal organs and other internal surfaces of the body) of the vagina. A similar condition termed stomatitis (inflammation of the mouth) is common in people who wear dentures. Candida can adhere to denture resin, and high sugar levels in the diet can also increase the adhesion by enhancing the production of a mannoprotein adhesive on the yeast cell surface. Systemic candidiasis is a more serious condition, when yeast cells proliferate in the circulatory system. This can occur after invasive surgical techniques, including the insertion of intravenous catheters to which the yeast cells adhere, providing a base from which the cells can bud and be disseminated.

All these examples illustrate that C. albicans is a classic opportunistic pathogen, normally kept in check but capable of flaring up in specific, predisposing conditions. It can be identified quite readily from clinical specimens by its ability to sprout hyphae when yeast cells at 37^oC are transferred to tubes of horse serum and incubated for 3-5 hours (Fig. D). Only C. albicans and a few related pathogenic Candida species do this. But the fungus has a strong tendency to revert to the yeast phase after only a short period of hyphal growth. Figures E and F show this for horse serum incubated for 24 hours – the hyphae themselves have a beaded appearance, and they give rise to budding yeast cells at the sites where the hyphae of other fungi would form branches.

Leaf surface yeasts: The common occurrence of yeasts on leaf surfaces can be shown by the method in Figure G, where a healthy leaf (in this case from a birch tree) is pressed against the surface of an agar plate for several hours, then removed and the plate is incubated at room temperature. In this example, almost the whole of the leaf print consists of colonies of a single Candida-like dimorphic fungus. The centers of the colonies consist of a mass of yellow-colored yeast cells, but the fungus is extending across the agar as hyphae at the colony margin (arrowhead). Figures I-K show one of these colonies at increasing magnifications. Instead of branching, the hyphae produce clusters of budding yeast cells at the septa (hyphal cross walls). Older and fallen leaves often have a more diverse fungal community, shown for a fallen oak leaf in Figure H. Again, there are dimorphic fungi (unmarked arrowhead) but colonies of Mucor (arrow labeled m) and some darkly pigmented fungi (center of the leaf print) are also present. The darkly pigmented fungi commonly include Cladosporium species (not shown) and one of the dimorphic “black yeasts”, Aureobasidium pullulans (see Figure L).

Now folks, to some of you I have suggested that you do not use an antibacterial soap to wash your hands after playing in the dirt or the leaf piles or trees in your yard or neighborhood forest. That also goes for wandering around in old houses where the walls have mold on them.

Look carefully again at the leaf patterns in the dishes of figures G and H (Birch and Oak respectively). There is no actual leaf in the dish. The leaf was pressed in and removed. The leaf you think you see is the fungi that totally covered the leaf. What good would an antibacterial soap do you to eliminate the fungi you have all over your skin from handling these leaves? All that soap will do is give a significant advantage to the fungi by eliminating its bacterial competition. What you need to wash up with after playing with trees and leaves is an antifungal soap. Ah, you say you can’t find those at WalMart? Of course you can’t. Where you can find them is in health food stores. They are the homemade soaps containing only natural ingredients (no chemicals of synthetic origin) and containing essential oils. These are the kinds of soaps Lannie makes here and they are all we use. If you really want to start making your own soaps, ask her nicely and I’m sure she’ll send you complete instructions.

More Charity BS

Remember a few issues back where I was blasting the charities that didn’t get the money you donate to the actual victims or causes that they were collecting for? Well, what about a case where 100% of the money collected actually does get to the victims? Do those people then use the money to fix the problems for which that money was given? Sorry to say that the answer is not only “no” but “hell no!”

What am I talking about? Well, guess… what charity is everyone on radio and TV crying about right now? Hurricane Katrina relief for those poor victims in New Orleans. Oh, my, those poor people who are without homes or fresh water or clothing and shelter for their children. Surely we should give them all we can, right? Wrong! Here’s how they are spending your money.

On the heels of a report earlier this week that Katrina victims were using $2,000 debit cards to purchase luxury items like Louis Vuitton handbags, Houston police yesterday discovered the cards, provided by FEMA and the Red Cross, being used at local strip clubs. … The Houston Police Department just formed a task force to investigate the abuse of the cards, which were distributed to thousands of Katrina hurricane victims to provide for necessities, such as food, clothing and toiletries. On the first day, the police found the cards being used to buy beer while ogling exotic dancers. … Earlier this week, the New York Daily News reported that “profiteering ghouls” were using the debit cards in luxury-goods stores as far away as Atlanta. … Meanwhile, in Memphis, Tenn., residents told News Channel 3 they saw Hurricane Katrina survivors purchase designer jeans, high heels and purses with their $2,000 emergency debit cards. According to the report, one Katrina victim was spotted at a Cordova clothier buying stacks of $65 designer jeans. Another viewer reported spotting a survivor buying “over $700 in high heel shoes and purses” at a Memphis department store “while (her) younger children, most of them looked under the age of 3, looked like they haven’t showered in weeks.”

For the full story, go to: http://wnd.com/news/article.asp?ARTICLE_ID=46361