2. CONTENTS
1. SAPROPHYTIC FUNGI
• Humus formation
• Types of organic compounds decomposed by saprophytic fungi
2. PARASITIC FUNGI
• Fungi as plant pathogens
• Fungi as human pathogens
3. COPROPHILOUS FUNGI
4. KERATINOPHILIC FUNGI KKR1116 2
3. SAPROPHYTIC FUNGI
• The word saprophyte is derived from the Greek words “Sapros” and “Phyton” which
means putrid and plant respectively .As such its concerned with decaying plant
matter.
• Fungi which obtain their nutrients from dead organisms and these are mainly
responsible for recycling the components of dead plants are known as saprophytic
fungi.
• They obtain food by dissolving organic material
• CHARACTERISTICS : They are eukaryotic ,lack chlorophyll and non vascular , produces
enzymes (cellulase, phytase,lipase etc),found in dark /shady and moist habitat.
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5. IMPORTANCE OF SAPROPHYTIC FUNGI :
• They are the primary recyclers of nutrients.
• They break down organic matter so that the nitrogen ,carbon and minerals it contains
can be put back into a form that other living organisms can take up and use .
• They release enzymes to break down and digest the lignin,cellulose or chitin into
simple soluble compounds that can be absorbed by them and plants as nutrients.
• HUMUS FORMATION: Saprophytic fungi play a vital role in the formation of of brown or
black organic complexes which remain in dynamic state.Humus can be fractioned into
HUMUS , HUMIC ACIDS , FULVIC ACIDS and HYMETAMELANIC ACIDS.
• Aspergillus and Penicillium are the genera involved in the degradation of humic acid.
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6. TYPES OF ORGANIC COMPOUNDS DECOMPOSED BY SAPROPHYTIC FUNGI:
1.CELLULOSE STRUCTURE AND ITS DECOMPOSITION :
• Cellulose is an organic polymer consisting of linear chains of ß-D-glucose units and
are linked by ß(14) glycosidic linkages.
• Two ß-D-glucose units linked by ß(14) glycosidic linkage forms a disaccharide
called cellobiase. The cellulose are connected by hudrogen bonds and forms tightly
packed crystals . Cellulases hydrolyze the ß(14) glycosidic linkages of cellulose.
• Endoglucanases : hydrolyze internal bonds releasing new terminal ends .
• Exoglucanases : act on the existing or endoglucanase generated chain ends .
• Both enzymes release cellobiase molecules .
Eg, Pleurotus ostreatus , Pleurotus florida , Fusarium solani, Aspergillus niger etc
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8. 2. HEMICELLULOSE STRUCTURE AND ITS DECOMPOSITION :
• Hemicellulose belongs to a group of heterogenous polysaccharides.
• These polysaccharide contains many different sugar monomers which include xylose
,mannose ,galactose ,arabinose rhamnose, glucuronic acids and galacturonic acids.
Sugars are linked by ß1,4 and occasionally by ß1,3 glycosidic bonds.
• Hemicellulose helps in strengthing the cell wall by interaction with cellulose and in
some wallas with lignin.
• Hemicellulose devided into 2 categories –
Homoglycans – single monosaccharide type .eg- xylan ,mannan
Heteroglycans – more than one kind of monosaccharide .eg-glucomannans
,arabinoxylans.
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10. • Decomposition of hemicellulose involves 3 types of enzymes :
Endo –enzymes : which randomly cleaves the bonds between building blocks in the
polymer .
Exo-enzymes : cleaves either a dimer or monomer from the end of the
polysaccharide chain.
Glycosidase : which hydrolyzes the oligomers or disaccharides produced from
hemicellulose
• Examples of utilizing hemicellulose are species of Alternaria, Aspergillus , Fusarium ,
Penicillium etc.
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11. 3. LIGNIN STRUCTURE AND DECOMPOSITION :
• Lignin is a complex polymer of 3 kinds of aromatic alcohols bonded by three types of
bonds which are aryl,ether,and ester which provide lignin a three dimensional polymer
of intermediate size.
• Lignin +cellulose =lignocellulose
• Lignin derived molecules have long been considered to be of significance in the
formation of humus which is important in maintaining soil fertility.
• Decomposotion of lignin is brought about almost entirely by fungi and especially
Basiodiomycetes such such as members of Aphyllophorales and Agaricales .
• Lignin can be slowly degraded by white –rot fungi such as Phanerochaete
chrysosporium which produce an extracellular lignin peroxidase enzyme to commence
the degradation process.Others fungal strains produce manganese peroxidase and
Laccase enzymes that are also active in lignin breakdown .
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14. PARASITIC FUNGI
Parasitic fungi attack living organisms ,penetrate their outer defenses , invade them
and obtain nourishment from living cytoplasm thereby causing disease and
sometimes death of the host .Most pathogenic fungi are parasites of plant .
They enter the host through a natural opening such as stoma in a leaf , lenticel in a
stem or a wound in the plant .
Common diseases of plants caused by fungi mildews (eg, grapes ,onion ,tobocca) ;
the smuts (eg, corn ,wheat ); apple scab; brown rot of stone fruits and various leaf
spots , blights and wilts.
Major groups of fungi and the disease caused :
Perosporaceae – downy mildews
Erysiphaceae – powdery mildews
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15. Downy mildews of grapes – Plasmopora viticola
The smuts of corn – Ustilago maydis
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16. Ustilaginales –smuts
• Other groups include hymenomycetes, certain ascomycetes and particularly
deuteromycetes .
• OBLIGATE PARASITE – Those parasite which grows only on living tissues .Nowadays
pathogens of plant have been divided into 2 broad categories:
OBLIGATE PARASITE
BIOTROPHIC PARASITES NECROTROPHIC PARASITES
They derive their nutrients They derive the nutrients from
from living host cells. dead host cells , usually killed by
Eg, The rust fungi(basidiomycetes) the parasite in advance of
The powdery mildew( ascomycota) penetration. Eg, Botrytis cinera
causes grey mold
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18. • INFECTION PROCESS: Spores of a pathogenic fungus falls on the leaves /stem of a
susceptible host germinateseach spore producing a germ tubetube grows on the
surface of the host until it finds an openingtube enters the host mycelial network
is formed within the invaded tissue.
• The germ tubes of some fungi produce special organs called appressoria from which a
needle like peg presses against ounctures the epidermis of the host after penetration ,
a mycelium develops .
• Many parasitic fungi absorb food from the host cell through the hyphal walls apressed
against the cell walls of the hosts internal tissues and others produce haustoria.
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19. FUNGI AS HUMAN PATHOGEN
• Fungal infection is caused by mold yeasts.
• A disease caused by a fungus on human and animal is called Mycosis. Mycosis are
frequently named after the part of body attacked.(eg, Bronchomycosis for respiratory
tract , Dermatomycosis for skin).
• Pathogens are categorized into 4 categories :
SUPERFICIAL - only the outer surface of the skin is invaded .
CUTANEOUS – where the keratinized tissues of the body are invaded.
SUBCUTANEOUS – where invasion occurs in the deeper layer of the skin, extending
into muscles, sometimes into the bone and may involve the lymphatic system .
SYSTEMATIC- where infection of lungs takes place by direct inhalation of fungal
spores . Infection may spread to all organs of the body and may cause death of the
host.
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21. FUNGI WHICH ARE ABLE TO INVADE HUMAN TISSUES ARE DIVIDED INTO TWO
GROUPS:
• THE PRIMARY PATHOGEN : they are capable of producing special kinds of fungak
infection in healthy individuals and have special clinical characteristics.
• THE OPPORTUNISTS : they will only invade the tissues of compromised host .
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22. COPROPHILOUS FUNGI
• They are a type of saprobic fungi that grow on animal dung.
• The distribution of coprophilous fungi is closely linked to the distribution of
herbivores on which they rely such as rabbits ,deer,cattle,horses and sheep.
• The hardy spores of coprophilous species are unwittingly consumed by herbivores
from vegetation and are excreted along with the plant matter. The fungi then
flourish in the feces before releasing their spores to the surrounding area.
• Coprinus radiatus & Panaeolus campanulatus grow exclusively on horse feces.
• Panaeolus sphinetrinus can grow on any feces or even just particularly fertile soil.
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24. • Chaetomium globisporum grows on dung of omnivores (rat droppings )
• Chaetomium rajasthanense grows on dung of carnivores (tiger feces)
• PROCESS: Coprophilous fungi releases spores into the environment eaten by
herbivoresplant digested passes through the animal’s
intestinesdefecatedfruiting bodies of the fungi grow from animal feces the
spores of the species then reach new plant material .
• Some species have developed means of discharging spores a large distance.
Eg, Genus – Pilobolus ; fruiting bodies of Pilobolus will suddenly rupture sending the
contents over 2 metres away.
• Animal feces provide an environment rich in nitrogenous material as well as various
enzymes from the animal’s digestive system.
• The spores themselves survive digestion by being particularly thick walled ,allowing
them to germinate in the dung with minimum competition from other organisms.
• The thick wall is often broken down during digestion ,readying the spore for
germination.
• Eg, Pilobolus kleinii, Mucor hiemalis, Sordaria fimicola
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26. KERATINOPHILIC FUNGI
• Various keratinophilic fungi along with some dermatophytes are responsible for
various skin infections .
• The most active keratinophilic fungi are dermatophytes and their correlates especially
–Microsporum, Trichophyton, Aphanoascus.
• In the kingdom Eumycota (true fungi ), two groups – Deuteromycetes & Ascomycetes
have keratinolytic members that occur commonly in soil as keratin decomposers.
• Some species are potential pathogens and can cause infections in the skin and scalp of
mammals (the dermatophytes)
• Keratinophilic –exhibiting affinity for keratin (as in hair,skin,feathers or horns) used
chiefly of fungi capable of growing on such materials .
• The biological function of keratinophilic fungi in the soil is the degradation of
keratinized materials such as hides, furs ,claws , nails, and horns of dead animals.
• In the soil these fungi live in their teleomorphic (=sexual) stages in the form of
cleistothecia , whereas in keratinized material ( host )they live in an anamorphic
(=asexual) stage .
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27. • Multiply asexually by producing enormous number of conidia and sexually by means
of fruiting bodies called ascomata ( when the keratin substrate is depleted )
• Eg , Chrysosporium spp ( mainly Chrysosporium indicum , Chrysosporium tropicum,
Chrysosporium keratinophilum)
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