classification of fungi.docx

MYCOLOGY
Unit Ist, Classification Of Fungi
DR VIJAY KUMAR SINHAL
DEPARTMENT OF PLANT SCIENCE
MJP ROHILKHAND UNIVERSITY,
BAREILLY, UP, INDIA

The main objective of the present lecture is to cover the topic and make
it easy to understand and interesting for our students/learners.
BLOCK – III : FUNGI – I
Unit –1 : General Characters and Classification of Fungi
OBJECTIVES

 Introduction of fungi
 General characteristics of fungi
 Occurance
 Thallus organisation
 Different forms of mycellium
 Cell structure
 Nutrition
 Heterothallism and Homothallism
 Reproduction
 Classification of fungi
 Classification based on taxonomy hierarchy
 Classification based on spore Production
 Classification of medically important fungi
 Classification based on route of acquisition
 Classification based on virulence
 Key points of the lecture
 Terminology
 Assessment Questions
 Bibliography
CONTENT

 Fungi is the plural of word fungus which is derived from the
latin word fungour.
 Fungi are achlorophyllas, heterotrophic
eukaryotic thallophytes.
 According to Alexopoulos (1962), the fungi include nucleated
spore bearing achlorophyllas organisms that generally
reproduce sexually and whose filamentous branched somatic
struture are typically surrounded by cell wall containing
cellulose or chitin or both.
 According to Bessey (1968), fungi are chlorophyll less non
vascular plants whose reproductive or vegetative structure do
not permit them to be assigned to position among
recognized group of higher plants.
 The branch of botany that deals with the fungi is called
mycology and the scientist who is concern with the fungi is
called a mycologist.
 P. A. Micheli known as father of mycology whereas E. J. Butler
refer to as father of Indian mycology.
 Fungi are non-green in color with the capacity to live in all
kinds of environments.
WHAT IS FUNGI ????

DIFFERENCE BETWEEN ALGAE AND FUNGI
Algae Fungi
The possess chlorophyll which in some of them is
masked by other pigments such as brown, red etc.
The fungi lack chlorophyll
With the help of chlorophyll, they are able to synthesize
their own food and thus are called autotrophic in their
mode of nutrition.
Lacking chlorophyll, the fungi are unable to synthesized
their own organic food. They get it readymade sources
either by living as parasites or saprophytes. For this
resions fungi are refer to as heterotrophic in their mode
of nutrition.
The algal thallus is composed of true parenchyma cells.
The unit f structure an algal thallus thus is a cell.
The fungal thallus which is termed das mycelium is not
formed by the division and differentiation of the cells but
composed of a false tissue called pseudoparanchyma.
Thus the unit of structure of a
fungus thallus is not a cell but hyphae.
The cell wall is typically composed of cellulose. The cell or hyphae wall is composed of fungus cellulose
or often called chitin.
The food reserve is chiefly in the form of starch. The reserve food invariably accumulated in the form of
glycogen and not starch.
The algae grow in the habitat where sun light is present. They generally have grown in dark and dim light.
They grow in water or in a damp soil and sometime as an
epiphytes rarely as endophytes.
They have grown in the wide variety of habitat; as
parasites in the tissue of plants and animals.
The sexual apparatus increases in complexity from the
simple to the higher forms.
There is a progressively and gradually simplification and
ultimate illumination of the sexual apparatus from the
lower to higher fungi.

SIMILARITIES BETWEEN ALGAE AND FUNGI
 Fungi and algae both prefer to live in moist environments. In fact, one of the benefits algae derive
from their symbiotic lichen relationship with fungi is their ability to survive on land in a moist
environment.
 Both algae and fungi are thallophytes (plant body not differentiated into root, stem and leaves)
 Both algae and fungi are placed together in the division thallophyta of cryptogams
 With the exception of blue green algae, majority of algae and fungi are eukaryotic
 Both fungi and algae are, in general, examples of organisms possessing a haploid nuclei. This
means they have only a single copy of each chromosome. By contrast, diploid organisms, such as
humans and most mammals, have two copies of each chromosome.
 Vascular tissue system is absent in both groups
 Both algae and fungi processes cell wall made of polysaccharides, chemical nature of cell wall
varies in algae and fungi
 Symbiotic members are present in both groups (algae with animals, fungi with roots of higher
plants, between algae and fungi as in lichens)
 Both groups can reproduce by vegetative reproduction by fragmentation and fission.
 Both algae and fungi can reproduce asexually by the production of various motile and non-motile
spores
 Sex organs are naked in both groups, no protective covering for sex organs in both groups

OCCURRENCE:
 Fungi are cosmopolitan and occur in air, water soil and on
plants and animals.
 They prefer to grow in warm and humid places. Hence, we
keep food in the refrigerator to prevent bacterial and
fungal infestation.
THALLUS ORGANIZATION:
 Except some unicellular forms (e.g. yeasts, Synchytrium),
the fungal body is a thallus called mycelium.
 The mycelium is an interwoven mass of thread-like
hyphae (Sing, hypha). Hyphae may be septate (with cross
wall) and aseptate (without cross wall). Some fungi are
dimorphic that found as both unicellular and mycelial
forms e.g. Candida albicans.
 The thallus may be two types: Unicellular and
filamentous.
GENERAL CHARACTERISTICS OF FUNGI
 Some of the most important characters of fungi are as follows: 1. Occurrence 2. Thallus
organization 3. Different forms of mycelium 4. Cell structure 5. Nutrition 6. Heterothallism and
Homothallism 7. Reproduction.

 Unicellular thallus: In some of the lower fungi, thallus is more or less a spherical, single celled
structure. At the time of reproduction it becomes a reproductive unit. Such fungi are called
holocarpic. In the unicellular holocarpic forms, the mycelium is absent e.g. Synchytrium. Some
holocarpic fungi (e.g., yeast) producing bud cells in succession and these remain attached to one
another in a chain. Such a chain of bud cells is referred to as pseudomycelium.
 Filamentous thallus: In most true fungi, the thallus is filamentous composed of Hyphae. Loosely
aggregated hyphae are collectively forms a network known as mycelium. Each hypha mayvary in
shapes and sizes. Branching of hyphae is dichotomous. On the basis of presence or absence of
septa the hyphae of mycelical fungi are of two types:
Nonseptate or aseptate hyphae: Mycelium contains numerous nuclei,lying in a common mass
of cytoplasm, without cross wall in the hyphae, E.g., oomycetes and zygomycetes. Such a
condition is known as coenocytic. However, septa may be laid down at the time of formation of
reproductive organs to delimit them from the rest of the vegetative hyphae, therefore called
Pseudosepta. E.g., Allomyces.
Septate Hyphae: Hyphae are septate and hyphal segments may contain one, two or more nuclei.
E.g., Ascomycotina, Basidiomycotina, and Deuteromycotina. There are two types of septa:
• Primary septa: Primary septa are formed in association with mitotic or meiotic nuclear division,
and they separate the daughter nuclei. These types of septa are found in Ascomycotina,
Basidiomycotina and their asexual states.
• Adventitious septa: Adventitious septa are formed in the absence of mitosis or meiosis and occur
especially in association with change in the local concentration of cytoplasm. These are found in
lower groups of fungi as mastigomycotina and zygomycotina.

DIFFERENT FORMS OF MYCELLIUM
 Different forms of mycelium refer to as the various shapes
and the functions of mycelium which modified according
to the circumstances. These includes the following forms:
a. Plectenchyma (fungal tissue): In a fungal mycelium,
hyphae organized loosely or compactly woven to form a
tissue called plectenchyma. It is two types:
 Prosenchyma or Prosoplectenchyma: In these fungal
tissue hyphae are loosely interwoven lying more or less
parallel to each other.
 Pseudoparenchyma or paraplectenchyma: In these
fungal tissue hyphae are compactly interwoven looking
like a parenchyma in cross-section.
b. Sclerotia (Gr. Skleros=haid): These are hard dormant
bodies consist of compact hyphae protected by external
thickened hyphae. Each Sclerotium germinates into a
mycelium, on return of favourable condition, e.g.,
Penicillium.
c. Rhizomorphs: They are root-like compactly interwoven
hyphae with distinct growing tip. They help in absorption
and perennation (to tide over the unfavourable periods),
e.g., Armillaria mellea. Rhizomorphs
Sclerotia
Prosenchyma and Pseudoparenchyma

d. Rhizoids: A rhizoid is a short, root like filamentous
branch of the thallus, generally formed in tufts at the base
of the thallus. These also function as anchoring and
absorbing, e.g., Rhizophydium, Rhizopus.
e. Appressoria (Sing. appressorium): It is a terminal
simple or lobed swollen mucilaginous structure of
infecting hyphae which adheres to the surface of the host
or other substratum and helps in the penetration of the
infection hyphae. These are formed by some parasiticfungi
such as powdery mildews and rust
f. Haustoria (Sing. haustorium): A haustorium is an organ
that is developed from a hypha usually performing the
function of absorption. They are characteristic of obligate
parasites. They vary in shape and may be knob like or
button shaped, elongated, finger-like or branched. They
secrete some specific enzymes which hydrolyse the
protein and carbohydrates of the host plant.
g. Hyphal traps (Snares): The predacious fungi develop
sticky hyphae or network of hyphal loops known as hyphal
traps or Snares. They help in capturing nematodes.
h. Stromata: These are compact somatic structures much
like mattresses. Fructifications are generally formed on or
in them.
Rhizoids
Appressoria
Hyphal traps
Hostorium

CELL STRUCTURE
 Fungi are the eukaryotic organisms.
 The cell wall determines the characteristic
shape of a cell. It protects the cell from osmotic
lysis and also acts as a binding site forsome
enzymes.
 The chemical composition of the cell wall is
not the same in all fungi. Chitin is
characteristically present in the cell walls of
most fungi. The chitin in fungal cell wall is not
strictly identical with animal chitin, and the
formula (C22H54N4O21)n has been suggested for
the fungal chitin: It is a polymer of N-
acetylglucosamine.
 The cytoplasm at hyphal tip contains Golgi
vesicles called chitosomes which filled withcell
wall materials.
 Nucleus and mitochondria are found to
connect with ER. Nucleus divides by
intracellular mitosis called karyochoresis
where nuclear envelop remain intact during
nuclear division and internal spindle develop.
Reserve food is glycogen and oil.
Cell Wall
Category
Taxonomic Group Representative
Genera
Cellulose-
Glycogen
Acrasiomycetes Polysphondylium,
Dictyostelium
Cellulose-
β-Glucan
Oomycetes Phytophthora,
Pythium
Cellulose–
Chitin
Hyphochytridiom
ycetes
Rhizidiomyces
Chitin–
Chitosan
Zygomycets Mucor, Phycomyces
Chitin-β-
Glucan
Chytridiomycetes Allomyces
Ascomycetes Neurospora
Deuteromycetes Aspergilllus
Basidiomycetes Fomes, Polyporus
Mannan-β-
Glucan
Ascomycetes Saccharomyces,
Candida

NUTRITION
 The fungi lack chlorophyll. Therefore, they cannot
synthesiz their own food. Depending on from where
and how they get nutrition, fungi are of following
types:
a. Saprotrophs: They obtain food from dead and
decaying organic matter. They secrete digesting
enzymes to outside which digest the substratum and
then absorb nutrients, e.g., Mucor, Agarious,
Rhizopus etc.
b. Parasitic: They obtain food from living organisms.
They may be facultative or obligate. Facultative
parasites grow on a variety of tissues e.g., Ustilago.
The obiigate- parasites growonly upon suitable host,
e.g., downy mildews. The parasitic fungi that grow
on surface of host cells and absorb food through
haustoria are called ectoparasites or ectophytic
parasites (e.g., Mucor, Erisphae). When parasitic
fungi grow inside the host tissue are called
endoparasites or endophytic parasites (e.g.,
Pythium, Puccinia).
c. Predacious: Some soil fungi develop ring-like noses
to trap annelids, nematodes etc. e.g., Arthrobotrys,
Zoophagus, Dactylella etc.
Saprotrophs
Predacious fungi trap nematode
Parasitic fungi on ladybug

d. Symbiotic: They live in mutualistic relationship with another organism by which both are
benefited. The two common examples are lichens and mycorrhiza.
 Lichens are symbiotic associations between fungi and algae. The fungal partner is a member of
ascomycetes or basidiomycetes that provides water and nutrients, while the algal partner is a
green alga or cyanobacteria that prepares food by photosynthesis.
e. Mycorrhizas: or mycorrhizae are the mutualistic symbiotic associations between soil fungi and
the roots of most plant species. According to the carbohydrate theory (Bjorkman, 1949), the
plants that grow in soils deficient in P and N, and high intensity light develop mycorrhizas.
 The two most common types of mycorrhizas are the ectomycorrhizas (ECM) and the
endomycorrhizas (also known as arbuscular mycorrhiza). The two groups are differentiated by
the fact that the hyphae of ectomycorrhizal fungi do not penetrate the cell wall of the plant’s
root cells, while the hyphae of arbuscular mycorrhizal fungi penetrate the cell wall.
(A) Lichen with (B) internal structure Plant showing (C) with and (D) without mycorrhizae

 HETEROTHALLISM AND HOMOTHALLISM
 A. F. Blakeslee (1904) discovered mating types or
genetically distinct strains in Mucor.
 He called fungi with different mating types are called
heterothallic and fungi without mating types are
called homothallic.
 Nowadays we call some fungi and algae homothallic if
both male and female gametes produce in the same
individual can fertilize each other and heterothallic if
the gametes can only be fertilized by gametes from
another individual of the same species.
Heterothallism introduces variations in the species.
 REPRODUCTION
 In fungi reproduction may take place by three
methods; vegetative, asexual and sexual.
 During asexual and sexual reproduction processes
spores are the essential structures. The spores formed
after meiosis are called meiospores (e.g., ascospores,
basidiospores and sporangiospores) and those
resulting from mitosis, called mitospores (e.g.,
mitospores, zoospores, aplanospores, conidia,
uredospores).

 The diploid body produced as a result of sexual fusion
is known as zygote which in lower fungi is termed as
resting spore, oospore or zygospore.
 In higher fungi, the zygote is represented by a diploid
nucleus produced in a cell (ascus or basidium). This
diploid nucleus after undergoing meiosis results in
the formation of haploid nuclei serving as centres for
haploid sexual spores called ascospores and
basidiospores.
 Vegetative reproduction: In this type of
reproduction, a part of mycelium separate and forms
a new individual. The various methods of vegetative
reproduction are:
a. Fragmentation: The hyphae break into small
fragments. Each piece upon getting suitable
conditions, germinates to form a new mycelium.
b. Fission: This method involves the splitting of cells
into two daughter cells by the formation of a
constriction followed by a cell wall formation.
c. Budding: A small bud formed from the parent cell
which gradually increases in size and receives a part
of nucleus. A cell wall is formed which separates the
daughter cell from the parent cell.
Fragmentation

d. Sclerotia: These are perennating bodies formed by
the compact masses of interwoven hyphae. Sclerotia
under suitable conditions germinate to form new
individuals e.g. Claviceps, Sclerotinia.
e. Rhizomorphs: These are root-like elongated
mycelial strands. They remain dormant under
unfavourable conditions and under favourable
conditions develop into a new mycelium.
 Asexual reproduction: It commonly take place
through spores, either motile or non-motile and
form in a specialized part of mycelium. The various
types of spores are:
a. Zoospores: These are commonly found in lower
fungi e.g., Saprolegnia, Pythium etc. They are naked
spores, which after swarming, encyst, secrete a cell
wall and germinate by germ tube into a thallus. They
are equipped with one or two flagella
b. Sporangiospore: The sporangiospores or
aplanospores are nonmotile and lack flagella and are
formed inside the sporangium e.g. Mucor, Rhizopus.
These spores may by uninucleate or multinucleate
and possess two-layered cell wall.
Rhizomorph
Zoospores
Sclerotia
Sporangiospores

c. Conidia: They are produced externally on branched
or unbranched hyphal tips termed as conidiophores.
The conidia may be formed singly or in chains. The
conidial chains may be basipetal or acropetal in
succession. Conidia may be uninucleate or
multinucleate. The latter type is more common in
the members of the form class Deuteromycetes.
d. Oidia: They are produced by fragmentation of
hyphae from apex to base. Each cell thus formed
rounds off and separates as a spore which under
favourable circumstances germinates and forms the
mycelium.
e. Chlamydospores: They are formed by rounding off
and enlargement of terminal or intercalary cells of a
hypha. These can be single or formed in chains.They
do not separate from the hyphae but remain viable
and germinate under favourable conditions.
f. Ascospores: An ascospore are produced inside an
ascus during the optimal condition. This kind of
spore is specific to fungi classified as ascomycetes.
g. Uredospores: A thin-walled, red, summer spore of
a rust fungus, produced usually on the leaves or
stems of grasses.
Conidia
Oidia
Chlamydospores
Ascospores

h. Basidiospores: These spore produced by
Basidiomycete fungi. They typically each containone
haploid nucleus that is the product of meiosis, and
they are produced by specialized fungal cells called
basidia.
 Sexual reproduction: It involves the formation and
fusion of gametes. Sexual reproduction found in all
groups of fungi except deuteromycetes or fungi
imperfecti. Sexual reproduction has three distinct
phases i.e. plasmogamy (protoplasmic fusion),
karyogamy (fusion of nuclei) and meiosis (reduction
division of zygote). The various methods of sexual
reproduction in fungi are as follows:
a. Planogametic copulation: This is simplest type of
sexual reproduction. In this process fusion of two
gametes of opposite sex or strains takes place where
one or both of the fusing gametes are motile
(flagellated). It results in the formation of a diploid
zygote. This process is usually of these types:
 Isogamy: In this process fusing gametes are
morphologically similar and motile but
physiologically dissimilar. These gametes are
produced by different parents, e.g. Synchytrium.

 Heterogamy: When the fusing gametes are
morphologically as well as physiologically
different, the process is known asheterogamy.
Heterogamous reproduction is of two types:
anisogamy and oogamy. Anisogamy consists
of the fusion of two motile gametes where the
male gamete issmall and more active than the
femalegamete, e.g., Allomyces. In oogamy the
motile male gamete (antherozooid) fuses
with the large, non-motile female gamete
(egg or ovum) e.g., Synchytrium etc.
b. Gametangial contact: In this process two
gametangia of opposite sex come in contact
with one another. The male gametangium
(antheridium) transfer male nucleus or
gamete into the female gametangium
(oogonium) either through a pore at the point
of contact or through a fertilizationtube, e.g.,
Phytophthora, Albugo, Pythium etc.
c. Gametangial copulation: In involves the
fusion of entire contents of two gametangia
to form a common cell called zygote or
zygospore, e.g., Mucor, Rhizopus.

d. Spermatization: Some fungi produce many minute, spore-like, single-celled structures called
spermatia (nonmotile gametes). These structures are transferred through agencies like water,
wind and insects to either special receptive hyphae or trichogyne of ascogonium. The contents
migrate into receptive structure. Thus dikaryotic condition is established, e.g. Puccinia.
e. Somatogamy: This takes place in fungi where formation of gametes is absent. In such fungi,
anastomoses takes place between hyphae and their somatic cells fuse to produce dikaryotic cells,
e.g, Agaricus, Peniophora etc.
Sexual reproduction in fungi: (A) Gametangia contact, (B-C-D) Planogametic copulation,
(E-F-G) Spermatization, (H) Gmaetangia copulation, (I) Somatogamy

 The classification of fungi is designed mainly for practical application but it also bears some
relation to phylogenetic considerations.
 The division of mycota, or fungi and moulds, includes the true slime moulds (Myxomycetes), the
lower fungi (Phycomycetes), and the higher fungi (Eumycetes).
 The fungi can be classified according to the various parameters including;
o Classification based on taxonomy hierarchy
o Classification based on spore Production
o Classification of medically important fungi
o Classification based on route of acquisition
o Classification based on virulence
o Classification based on taxonomy hierarchy:
 Alexopolous and Mims proposed fungal classification in 1979. They place the fungi including the
slime molds in the kingdom mycetae of the super kingdom Eukaryota which, in addition, includes
four other kingdoms. They divide the kingdom mycetae into three divisions namely:
 Gymnomycota
 Mastigomycota
 Amastigomycota
 The division is subdivided into subdivision, classes, sub-classes, and orders.
CLASSIFICATION OF FUNGI

 Division I: Gymnomycota: It includes phagotrophic organism devoid of cell walls.
Thisdivision comprises two subdivisions; Acrasiogymnomycotina and Plasmodiogynomycotina.
1. Subdivision : Acrasiogymnomycotina: It includes a single class Acrasiomycetes.
Class 1. Acrasiomycetes : Lacks flagellated cells except for one species. The class comprises:
Sub class 1. Acrasiomycetidae
Sub class 2. Dictyosteliomycetidae
2. Subdivision: Plasmodiogymnomycotina: It is divided into two classes:
Class 1. Protosteliomycetes
Class 2. Mycomycetes: It includes the true slime mold and comprises three sub class namely:
Sub class 1. Ceratiomyxomycomycetidae, 1 Order : Ceratiomyxales
Sub class 2. Mycogasteomycetidae, 4 Orders: Liceales, Echinosteleales, Trichlales, Physarales
Sub class 3. Stemonitomycetidae, 1 Order: Stemonitales
 Division II: Mastigomycota: Includes fungi with absorptive nutrition, unicellular
or filamentous, mycelium coenocytic. It comprises two sub divisions:
1. Sub division: Haplomastigomycotina: Includes fungi with uni-or, bi-flagellate zoospores.
Class 1. Chytridiomycetes– Fungi producing zoospores furnished with a single whiplash
flagellum inserted at the posterior end.
Class 2. Hyphochytridiomycetes- Motile cells with a single tinsel flagellum inserted at the
anterior end.
Class 3. Plasmodiophoromycetes- Parasitic fungi producing biflagellate motile cells with
both the flagella of whiplash type inserted at the anterior end.
2. Sub division: Diplomastigomycotima: Sexual reproduction ooagamous, zoospores
biflagellate.
Class 1. Oomycetes, 4 Orders: Lagenidiales, Saprolegnailes, Leptomitales, Peronosporales

 Division III: Amastigomycota: Fungi with absorptive nutrition, motile cells
lacking,mycelium aseptate or septate. This includes four sub divisions:
1. Sub division: Zygomycotina
Class 1. Zygomycetes – it includes six orders.,
Class 2. Trichomycetes – it comprises five orders.
2. Sub division: Ascomycotina: Fungi usually with a septate mycelium producing
haploid ascospores in sac like cells called asci.
Class 1. Ascomycetes: Divided into five sub classes:
Sub class 1. Hemiascomycetidae- comprising three orders.
Sub class 2. Plectomycetidae- Five orders
Sub class 3. Hymenoascomycetidae – Ten orders
Sub class 4. Laboulbeniomycetidae – Two orders
Sub class 5. Lowloascomycetidae – five orders
3. Sub division 3: Basidiomycotina: Septate mycelium, produces basidiospores,
exogenously onvarious types of basidia.
Class 1. Basidiomycetes: it is split into 3 sub clases:
Sub class 1. Holobasidiomycetidae
Sub class 2. Phragmobasidiomycetidae
Sub class 3. Teliomycetidae
4. Sub division: Deuteromycotina: It includes imperfect fungi in whichsexual stage
isunknown. It comprises a single class.
Class 1. Deuteromycetes
Sub class 1. Blastomycetidae
Sub class 2. Coelomycetidae
Sub class 3.Hyphomycetidae

Division mycota: These include non green, nucleated thallophytes which are saprophytes or parasite in nutrition.
Subdivision Myxomycotine: Thallus is achlorophyllus, multinucleated mass of protoplasm called plasmodium, e.g., slime molds.
Subdivision Eumycotina: All the fungi except the slime molds are included in this subdivision.
Lower fungi: They have simple thallus which are unicellular and others filamentous (mycelium), usually septa is not present.
Class Chytridiomycetes: Motile cells have a single flagellum of whiplash type inserted at the posterior end.
Class Hyphochytridiomycetes: Motile cell spossesses a single flagellum of tinsel type inserted at the anterior end.
Class Plasmodiophoromycetes: Motile cells are biflagellated (whiplash type), but one is longer than the other one.
Class Oomyceters: Motile cells are biflagellated, nearly equal length, one of these points forwards and the other trails behind.
Class Zygomycetes: Motile cells are absent. Asexual reproduction take place by sporangiospores.
Class Trichomycetes: Motile cells are lacking. Asexual reproduction take place by conidia.
Higher fungi: The somatic phase consists mostly of a mycelium which is usually septate.
Class Ascomycetes: The characteristic spores called ascospores are produced endogenous within sac like structure called asci.
Class Basidiomycetes: Characteristic spores called basidospores are produced exogenous on club shaped structure called basidia.
Class Deuteromycetes: Sexual stage is unknown. The somatic phase consist a septate mycelium which multiply by conidia.
 Martin (1965) proposed a classification according to the spore formation in fungi. The outline of
classification is given;

A more natural system of classification of fungi was proposed by Ainsworth (1973) which has
been accepted by many mycologist today like Webster (1980), Bilgrami (1985 and Dube (1987).

o Classification based on spore production:
 On the basis of the organisation of the vegetative thallus, the morphology of reproductive
structures, the way of spores production and particular life cycle involved the kingdom mycota is
classified into following divisions.
 Phycomycetes
• It includes the simplest type of fungi. It is also called as Algae-Fungi because most
of thecharacteristics of them are similar to algae like Vaucheria.
• They have simple thallus which is unicellular or coenocytic or aseptate filaments.
• They reproduce asexually by the formation of zoospores or non-motile spores.
• Sexual reproduction is isogamous or heterogamous which takes place by gametangial contact.
• The diploid phase is represented by zygote.
• Phycomycetes has been classified into subclasses: oomycetes and zygomycetes.
Oomycetes
• It range from a primitive unicellular thallus to a profusely branched filamentous mycelium.
• Many members of them are terrestrial and obligate parasites.
• Asexually they reproduce by biflagellate zoospores.
• Oogamous reproduction that involves the fusion of male and female gametes to form oospore.
• Oospore undergoes meioses to produce haploid biflagellate zoospores.
• Example; Phytophthora infestans (causes potato blight).

 Zygomycetes
• The group is named zygomycetes because a diploid resting spore called the zygospore is
formedduring the life cycle.
• They are mostly saprophytic, some others are parasites on plants and animals.
• The vegetative body is mycelium which is well developed, profusely branched and coenocytic.
• The absence of motile sexual or asexual cells.
• The asexual reproduction takes place by sporangiospores, aplanospores or by conidia.
• Sexual reproduction occurs by conjugation of gametangia resulting in the formation of
zygospore.
• Examples; Rhizopus, Mucor etc.
 Ascomycetes
• The species of ascomycetes are called the sac fungi because they produce sexual pores
within the sac-like vascus.
• Ascomycetes are mostly terrestrial occurring as saprophytes or parasites.
• They have well-developed, branched, septate mycelium except yeast. Yeast is a unicellular fungus.
• Asexually they reproduce by non-motile spores, conidia, oidia or chlamydospores.
• Sexual reproduction takes place by the fusion of gametangia of opposite mating types.
• There is absence of motile cells.
• Examples, Saccharomyces cerevisiae, Penicillium, Aspergillus etc.

 Basidiomycetes
• The members of basidiomycetes are saprophytic or parasitic. The group is named
basidiomycetesas they produce the basidiospores at the club-shaped basidium during
sexual reproduction.
• Mycelium is highly developed, profusely branched and septate.
• The mycelia are differentiated into two mating types; (+ve) and (-ve).
• There are two kinds of mycelium; primary mycelium and secondary mycelium.
• Asexual reproduction takes place by fragmentation, budding, oidia, conidia or chlamydospore.
• The dikaryotic cell is formed during sexual reproduction.
• The absence of motile cell throughout the life cycle.
• These are the most advanced fungi as their fructifications are often large and prominent.
• Examples; Mushrooms, Puccinia, Ustilago etc.
 Deuteromycetes (The Imperfect Fungi)
• Deuteromycetes compromises more than 17000 species of the diverse habits and habitats. It is
considered as an artificial class of fungi. They Iack sexual Reproduction.
• The fungi are saprophytes as well as parasites.Parasitic fungi cause serious diseases to plants,
animals including human beings.
• Some of them are unicellular while others are multicellular.
• They reproduce asexually by conidia along with some other types of spores.
• The sexual reproduction is entirely absent.
• The asexual stage or imperfect stage in Deuteromycetes is well defined. But the sexual or perfect
stage is absent in life cycle, therefore, they are called ‘Fungi Imperfecti’.

• Example; Alternaria, Fusarium, Helminthosporium etc.
o Classification based on medically important fungi
 Mycoses are classified as superficial, cutaneous, subcutaneous, or systemic (deep) infections
depending on the type and degree of tissue involvement and the host response to the pathogen.
a. Superficial mycoses (or tineas): Occur in the tropics and are restricted to the outer surface of
the hair and skin, e.g., Piedraia hortae.
b. Cutaneous mycoses: There are three genera of fungi (Microsporum, Trichophyton and
Epidermophyton) that commonly cause disease in the non-living tissues of skin, hair, or
nails/claws of people and animals, by growing in a zone just above where the protein keratin is
deposited.
c. Subcutaneous mycoses: They are normally saprotrophic inhabitants of soil, particularly in
tropical and subtropical areas of Africa, India and South America.
d. Systemic mycoses are infections that affect the whole body. We divide these into mycoses due
to primary (usually dimorphic) virulent pathogens, and those due to opportunistic pathogens.
o Classification based on route of acquisition
a. Infecting fungi may be either exogenous or endogenous.
b. When classified according to the route of acquisition, a fungal infection may be designated as
exogenous or endogenous in origin.
c. If classified as exogenous, an infecting organism may be transmitted by airborne, cutaneous, or
percutaneous routes.
d. An endogenously-acquired fungal infection may be acquired from colonization or reactivation

of a fungus from latent infection.
o Classification based on virulence
 Primary pathogens can establish infections in normal hosts.
 Opportunistic pathogens cause disease in individuals with compromised host defense
mechanisms.
• Deep mycoses are caused by primary pathogenic and opportunistic fungal pathogens.
• The primary pathogenic fungi are able to establish infection in a normal host; whereas,
opportunistic pathogens require a compromised host in order to establish infection (e.g., cancer,
organ transplantation, surgery, and AIDS).
• The primary deep pathogens usually gain access to the host via the respiratory tract.
Opportunistic fungi causing deep mycosis invade via the respiratory tract, alimentary tract, or
intravascular devices.
• The primary systemic fungal pathogens include Coccidioides immitis, Histoplasma capsulatum,
Blastomyces dermatitidis, and Paracoccidioides brasiliensis.
• The opportunistic fungal pathogens include Cryptococcus neoformans, Candida,
Aspergillusspp., Penicillium marneffei, the Zygomycetes, Trichosporon beigelii, and Fusarium
spp.

 Fungi is the plural of word fungus which is derived from the latin word fungour.
 Fungi are achlorophyllas, heterotrophic eukaryotic thallophytes.
 The branch of botany that deals with the fungi is called mycology and the scientist who is
concern with the fungi is called a mycologist.
 P. A. Micheli known as father of mycology whereas E. J. Butler refer to as father of Indian
mycology.
 Fungi are eukaryotic organisms means they have true nucleus which are enclosed in membranes.
 They are non-vascular organisms. Xylem and Phloem are absent.
 Fungi have cell walls (plants also have cell walls, but animals have no cell walls).
 There is no embryonic stage for fungi.
 They reproduce by means of spores. There are sexual and asexual spores. Sexual spores are
Oospores, Zygospores, Ascospores, Basidiospores, etc. and Asexual spores are Sporangiospores,
Aplanospores, Zoospores, Conidia, etc.
 Depending on the species and conditions both sexual and asexual spores may be produced.
 They are typically non-motile.
 Fungi exhibit the phenomenon of alteration of generation. They have both haploid and diploid
stage.
KEY POINTS OF THE LECTURE

 Fungi are achlorophyllous, which means they lack the chlorophyll pigments present in the
chloroplasts in plant cells and which are necessary for photosynthesis.
 As they are achlorophyllous, therfore, they do not have the ability to make their own food.
 The vegetative body of the fungi may be unicellular or composed of microscopic threads called
hyphae. Hyphae can grow and form a network called a mycelium.
 Yeasts are unicellular fungi that do not produce hyphae.
 The structure of cell wall is similar to plants but chemically the fungi cell wall are composed of
chitin (C8H13O5N)n.
 Fungi are heterotrophic organisms. They obtains its food and energy from organic substances,
plant and animal matters.
 Fungi digest the food first and then ingest it to accomplish this the fungi produce exoenzymes
like Hydrolases, Lyases, Oxidoreductase, Transferase, etc. Fungi store their food as starch.
 Fungi are saprophytes (gets energy from dead and decaying matters), or parasites (lives in a host,
attack and kill) or symbionts (mutually beneficial).
 Optimum temperature of growth for most saprophytic fungi is 20-30°C while (30-37)°C for
parasitic fungi. Growth rate of fungi is slower than that of bacteria.
 Reproduction in fungi is both by sexual and asexual means. Sexual state is referred to as
teleomorph (fruiting body), asexual state is referred to as anamorph (mold like).

 Asexual reproduction methods are: fragmentation, somatic budding, fission, asexual spore
formation. Sexual methods are: gametic copulation, gamate-gametangium copulation,
gametangium copulation, somatic copulation and Spermatization.
 Some fungi are macroscopic and can be seen by naked eyes. Mold or mushrooms are examples of
macroscopic form of fungi.
 In 1991, a landmark paper estimated that there are 1.5 million fungi on the Earth. Only about 300
species of fungi are infectious to human.
 The classification of fungi is designed mainly for practical application but it also bears some
relation to phylogenetic considerations.
 The fungi can be classified according to the various parameters including; Classification based on
taxonomy hierarchy, Classification based on spore Production, Classification of medically
important fungi, Classification based on route of acquisition, Classification based on virulence
 Alexopolous and Mims proposed fungal classification in 1979. They place the fungi including the
slime molds in the kingdom mycetae. They divide the kingdom mycetae into three divisions
namely: Gymnomycota, Mastigomycota and Amastigomycota
 Martin (1965) proposed a classification according to the spore formation in fungi and divide the
division mycota into two sundivision; Myxomycotina and Eumycotina.
 Classification based on medically important fungi divided the fungi into superficial mycoses,
cutaneous mycoses, subcutaneous mycoses and systemic mycoses.

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