Transcript Slide 1

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.
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 energyrich carbon compounds
manufactured by other organisms.
Fungi have evolved enzymes that
can digest some extremely tough
substrates.
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
wall of fungus-chitin
cytoplasm
sporangium
columella
spores
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.
Rhizopus – asexual reproduction
Sporangia are produced at the ends of the
sporangiophores.
The spores are white at first
Each sporangium contains
hundreds of non-motile,
asexual spores within a
delicate outer membrane
called a peridium.
but turn black as they ripen.
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.
swollen tip
dense protoplasm
columella
forms
columella
swells
thick wall
spores form
spores
blown in
wind
collapsed
wall
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
Mushrooms are well known as a
FUNGI :
tasty food. Other fungi are used
3. Fungi in the food industry –
4. Fungi in medicine –
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.
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 flipflops 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.