FUNGI Click here for a picture introduction to FUNGI. Fungi differs from green plants as they lack chlorophyll and cannot synthesis their own organic food. They are heterotrophic, which means that they depend on energy-rich carbon compounds manufactured by other organisms. Fungi have evolved enzymes that can digest some extremely tough substrates. Chitin (insect exoskeletons), keratin (skin, hair, horn, feathers), cellulose (most plant debris) and lignin (wood), nourish many fungi, though cellulose and lignin remain completely unavailable to almost all animals. Fungi have learned to cope with environmental extremes. They can grow at temperatures as low as -50 Celsius and as high as 60 Celsius. Click here for a picture introduction to FUNGI.

There are about 900 000 species and three common ones are: BREAD MOULDS MUSHROOMS YEASTS

There are two major physical reasons for the incredible success the fungi enjoy. The first is the fungal spore, the second the fungal hypha.  Spores permit rapid dispersal and a kind of scattershot saturation of the biosphere - fungal spores are everywhere.  Hyphae permit the thorough and intimate exploration and exploitation of newly available substrates. SPORES The non-motile microscopic spores of fungi are often produced very quickly and in enormous numbers. Spores are dispersed by wind, water, or animals, and they can often survive long periods, sometimes even years, of unfavourable conditions.

HYPHAE These are the vegetative, filamentous, tube-like organs of most fungi.  When a spore germinates, what emerges is a hypha (sometimes more than one hypha), which grows at its tip. The picture below shows hyphae emerging from spores and looking for food. In order to explore the territory properly, hyphae must branch as they spread out.  This is shown in the drawing below. A young fungal colony arising from a single spore (the black dot in the middle). Its strong, waterproof, chitinous hyphae, its richly branched growth pattern, the  digestive enzymes it secretes at its growing tips, and the hydrostatic pressures it can bring to bear - all these make it ideally suited for actively penetrating, exploring and exploiting solid substrates. 

Rhizopus – bread mould The rhizopus species grow best on moist, organic substances, especially in warm dark places. It consists of a tangled mass of hyphae and there are no roots, stems or leaves. The plant body is called a thallus. Each hypha is branched and the entire plant thallus is known as a mycelium. Each hypha is also non-septate as there are no transverse walls. The hyphae have a large vacuole filled with cell sap and the cytoplasm forms a continuous layer on the wall containing food reserves. There are many nuclei scattered throughout the cytoplasm. The non-septate hyphae are said to be coenocytic.

Rhizopus – structure Rhizopus hyphae are made up of: stolons that form the branch covering over the surface rhizoids that grow down into the substrate sporangiophores that grow up from the stolons Coenocytic hypha of Rhizopus Mycelium of Rhizopus sporangium wall of fungus-chitin cytoplasm spores columella vacuole many nuclei sporangiophore stolon rhizoid

Rhizopus – nutrition Rhizopus relies on complex organic food which must be absorbed from dead organic matter, it is therefore saprophytic. The rhizoids secrete digestive enzymes which change the complex foods into simple soluble ones which can be absorbed. The digested foods are absorbed in watery solution by the hyphae along with nitrates and phosphates. These compounds are then made into the organic material of the fungal protoplasm.

– asexual reproduction Rhizopus – asexual reproduction Sporangia are produced at the ends of the sporangiophores. The spores are white at first but turn black as they ripen. Each sporangium contains hundreds of non-motile, asexual spores within a delicate outer membrane called a peridium.

– asexual reproduction Rhizopus – asexual reproduction The swollen extension of the sporangiophore is called a columella, which protrudes like a balloon into the sporangium. When the spores are mature the sporangium wall either dries out to liberate the spores, or absorbs water to become soft so that the pressure of the columella bursts the wall, exposing the spores. The spores are very light and well suited to being dispersed by wind. thick wall spores form dense protoplasm swollen tip spores blown in wind columella swells collapsed wall columella forms

THE ECONOMIC IMPORTANCE OF FUNGI : 1. Decay or decomposition – Saprophytic fungi cause the decay of the remains of dead plants and animals. This is important because it returns essential nutrients to the soil and atmosphere. 2. Crop diseases – Many fungi cause disease in crop plants causing huge losses in man’s food supply and costing a large amount of money to control.

THE ECONOMIC IMPORTANCE OF FUNGI : Mushrooms are well known as a tasty food. Other fungi are used in the production of certain cheeses like Roquefort, Camembert and Stilton. Yeasts produce alcohol in beer, carbon dioxide in the process of baking bread, are necessary for making grape sugar in wine production and they are also used in the commercial production of vitamins. 3. Fungi in the food industry – 4. Fungi in medicine – Fungi are important in medicine because some of them can produce substances which kill bacteria and these are known as antibiotics. There are also a few human diseases caused by fungi. The best known ones are “ringworm” and “athlete’s foot”. These are caused by parasitic fungi which infect the skin surface.

FUNGI THAT CAUSE DISEASE IN HUMANS: The Basics on Tinea Infections Tinea (pronounced: tih-nee-uh) is the medical name for a group of related skin infections, including athlete's foot and ringworm. These infections are caused by several types of mold-like fungi called dermatophytes (pronounced: der-mah-tuh-fites) that live on the dead tissues of the skin, hair, and nails. These fungi are not really parasitic in the sense of attacking living tissue. They attack the dead cells of the epidermis, and cause a kind of dermatitis. The irritation caused by the fungus stimulates the skin cells to divide more rapidly. This means that more flakes of skin containing infective mycelium will be shed.

What is Athlete’s Foot? The medical name for athlete's foot is tinea pedis. Usually athlete's foot affects the soles of the feet and the areas between the toes, and it may also spread to the toenails. Athlete's foot can also spread to the palms of your hands, groin, or underarms if you touch your feet and then touch another area of your body. Athlete's foot doesn't just aggravate athletes; anyone whose feet tend to be damp or sweaty can get this infection. The fungi that cause athlete's foot thrive in warm, moist environments. The signs and symptoms of athlete's foot include itching, burning, redness, and stinging on the soles of the feet. The skin may flake, peel, blister, or crack. 

How can you prevent it? Athlete's foot is contagious. It's often spread in damp areas, such as public showers or pool areas. To prevent getting athlete's foot, dry your feet - and the spaces between your toes - thoroughly after showering or swimming. Use a clean towel. (Avoid sharing towels because doing so can spread the infection.) If you use public showers, like those in the locker room, wearing waterproof shoes or flip-flops is a good way to protect your feet.

How is it treated? A doctor can often diagnose athlete's foot simply by examining the affected area. Your doctor may also take a small scraping of the skin on your foot. This sample is then examined under a microscope or sent to a laboratory for culture to see if the fungi that cause athlete's foot are present. If you have athlete's foot, over-the-counter antifungal creams and sprays may solve the problem. Most mild cases of athlete's foot usually clear up within 2 weeks, but it is common for athlete's foot to recur (come back), so some people use medicated powders and sprays to prevent this from happening. If an athlete's foot infection is more serious, it can take longer than a couple of weeks to get better. In these cases, it's a good idea to see your doctor, who may prescribe a stronger antifungal cream, spray, or pill.

What is Ringworm? Ringworm, which isn't a worm at all, can affect not only the skin, but also the nails and scalp. Ringworm of the skin starts as a red, scaly patch or bump. Ringworm tends to be very itchy and uncomfortable. Over time, it may begin to look like a ring or a series of rings with raised, bumpy borders around a scaly center. This ring pattern gave ringworm its name, but not every person who's infected develops the rings. When ringworm affects the feet it's known as athlete's foot, and the rash, which is usually between a person's toes, appears patchy. Ringworm of the scalp may start as a small sore that resembles a pimple before becoming patchy, flaky, or scaly. It may cause some hair to fall out or break into stubbles. It can also cause the place where the infection is to become swollen, tender, and red. Ringworm of the nails may affect one or more nails on a person's hands or feet. The nails may become thick, white or yellowish, and brittle. It's unusual for teens to get ringworm of the nails, though.

Can you prevent Ringworm? The most common sources of the fungi that cause tinea infections are other people. It is also possible to get tinea infections from contact with animals, like cats and dogs. It can be difficult to keep from getting ringworm because the dermatophyte fungi are very common. To protect yourself against a tinea infection it can be helpful to wear flip-flops on your feet in the locker room shower or at the pool and to wash sports clothing on a regular basis. Because fungi are on your skin, it is important to shower after contact sports and it is always a good idea to wash your hands on a regular basis, especially after touching pets. Ringworm is contagious and is easily spread from one person to another, so avoid touching an infected area on another person. If you discover a red, patchy, itchy area that you think may be ringworm, call your doctor.

How is Ringworm treated? Fortunately, ringworm is fairly easy to diagnose and treat. Most of the time, the doctor can diagnose ringworm based on how it looks. Sometimes the doctor will scrape off a small sample of the flaky infected skin to test for fungus. If you do have ringworm, the doctor will recommend an antifungal medication. A topical ointment or cream usually takes care of skin infections, but ringworm of the scalp and nails require oral antifungal medication. Your doctor will decide which treatment is best for you.