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ULTRA STRUCTURE OF
FUNGAL CELL AND
GROWTH
K R MICRO NOTES 1
INTRODUCTION
❖ FUNGI is the plural for the word FUNGUS which is derived from the
latin word FUNGOUR, which means to flourish.
❖ Fungi can be defined as eukaryotic, spore bearing, achlorophyllous
organisms and Thallophytic plants that may reproduce sexually or
asexually and whose filamentous, branched and somatic structures
are typically surrounded by cell walls containing chitin, cellulose, or
combination of both.
❖ The branch of biology which deals with the study of fungi is called
mycology (Mykes = Mushroom or fungi, logos = Discourse)
K R MICRO NOTES 2
❖ They are ubiquitous in terrestrial and fresh water habitats,
less in the marine environment.
❖ They are cosmopolitan in distribution
❖ Characteristically, they are saprophytic, parasitic, symbiotic
or hyper parasitic in nature.
❖ They are also used for preparation of different industrial
substances including antibiotics, enzymes and acids etc..
K R MICRO NOTES 3
ULTRASTUCTURE OF FUNGAL
CELL
K R MICRO NOTES 4
Cross-section view of a typical fungal cell
K R MICRO NOTES 5
CELL WALL
 The main identifying characteristics of fungi is the make up of their cell
walls.
 The composition of the fungal cell wall is rather variable.
 It gives strength and shape to fungi.
 Iit provides protection for the protoplasm from UV RAYS(presence of
melanin)
 Glucan and Chitin are components of the primary wall, proteins are the
components on the secondary cell.
 Ability to resist Lysis by organic solvents such as enzymes, toxins and
osmotic integrity.
 They have ability to bind with metal ions.
 Except slime moulds (Myxomycetes) ,the fungal cell consist of a rigid
cell wall and cell organelles.
6
 The cell wall of Ascomycotina
and Basidiomicotina contains
chitin (β 1,4 N-
acetylglucosamine ).
 In the Zygomycotina, the chitin
fibres are modified to produce
poly-β-(1,4)glucosamine, which
is called chitosan.
 The cell walls of oomycetes
contain cellulose and lack chitin.
K R MICRO NOTES 7
CELL MEMBRANE
❖ In fungal cells, the living protoplast
is enclosed in a cell membrane,also
called the plasma membrane or
plasmalemma.
❖ It is delicate, extremely thin
semipermeable membrane.
❖ The principal components of
plasmalemma are proteins and
lipids.
❖ At the surface of plasmalemma
,some membrane structures known
as lomasomes and
plasmalomosomes have been
reported.
❖ Glucose residues, Glucosamine,
sterols(ergosterol), Mannose are
present.
K R MICRO NOTES 8
CYTOPLASM
 Within the plasma membrane ,is the colourless cytoplasm in which
sap-filled vacuoles may occur.
 Immersed in the cytoplasm are structures known as the organelles
and inclusions.
 The organelles are living structures,each with a specific function.The inclusions
are dead,have no specific function and thus are not essential to cell survival.
 Among the cell organelles are included the E.R,mitochondria,ribosomes,Golgi
apparatus and vacuoles.
 Examples of inclusions are the stored foods( glycogen,oil drops) pigments and
secretory granules.
K R MICRO NOTES 9
NUCLEUS
❖ The cytoplasm contains one, two or more
globose or spherical nuclei
❖ It measures up to 1-3 µm in diameter.
❖ Structurally the nucleus consists of :
❖ A central dense body(nucleolus).
❖ Chromatin strands.
❖ The whole structures surrounded by a
definite nuclear membrane.
❖ Under the electron microscope, nuclear
membrane is seen to consist of 2 unit
membranes - inner and outer layers of
electron dense material.
❖ It has pores, at certain points and the
membrane is continuous with ER.
K R MICRO NOTES 10
ENDOPLASMIC RETICULUM
❖ Presence of endoplasmic reticulum in
fungal cytoplasm is observed through
electron microscope.
❖ It is made up of flattened sacs of
membrane- cisternae.
❖ It is composed of a system of
membranes or micro tubular structures
with small granules (ribosomes)
❖ In many fungi, the E.R is highly
vesicular.
❖ It is loose and irregular as compared
with cells of green plants.
K R MICRO NOTES 11
RIBOSOMES
❖ Ribosomes is found on the ER , others free floating in the
cytoplasm.
❖ They are proteinaceous bodies with high RNA content.
❖ They are concerned with protein synthesis .
❖ They aggregate to form polyribosomes (or polysomes)
K R MICRO NOTES 12
GOLGI BODIES( DICTYOSOMES)
❖ Moore and Muhlethaler in 1963 reported 3 flattened sacs in
Saccharomyces cells.
❖ Golgi Bodies or dictyosomes are found comparatively rarely in fungi
(except oomycetes).
❖ Not organized as stacks of flattened cisternae .
❖ Instead, the Golgi bodies of fungi appear as single tubular, cisternae that
vary in shape from cup-like to planar bodies.
❖ functionally equivalent to the stacked Golgi bodies.
❖ Major function is to process and package macromolecules (proteins) and
transportation of lipids around the cell.
K R MICRO NOTES 13
K R MICRO NOTES 14
MITOCHONDRIA
❖ Richard Altmann , in 1890, established cell organelles and called them
“bioblasts”. Carl Benda coined the term “mitochondria” in 1898.
❖ The cytoplasm contains small, usually spherical bodies known as the
mitochondria.
❖ Each mitochondrion is enveloped by a double membrane.
❖ The inner membrane is infolded to form the cristae which are in the form
of parallel flat plates.
❖ The mitochondria function as the power house of the cell.
❖ Mitochondria has its own machinery for transcription and translation of
organelle specific DNA.
K R MICRO NOTES 15
VACUOLES
❖ Vacuoles are essential for cell function in
fungi. Fungi are characterized by the
presence of spherical to tubular vacuoles.
Vacuoles are found in the old cells of
hyphae. The end of hyphal tip of young
hyphae lacks vacuole.
❖ Vacuoles are surrounded by a membrane
known as tonoplast.
❖ The function of the vacuoles is to provide
the turgor needed for cell growth and
maintenance of cell shape.
❖ Besides osmotic function,it stores reserve
materials(Volutin- polymetsphosphate ; in
yeasts), pigments , amino acids and
hydrolases.
K R MICRO NOTES 16
LYSOSOMES
❖ Thornton (1968) described them as “ Autophagic vesicles”.
❖ They have been described only in Botrytis cinerea and
Phycomyces.
❖ They are thought to be derived from Golgi cisternae.
❖ Simple lysosomes have a diameter of 400nm and are bound by a
unit membrane.
K R MICRO NOTES 17
VESICLES
❖ The term vesicle is used for any cell or organ that is inflated by
the stuff that is used to store. (swollen end cells)
❖ This are generally formed by Endomycorrhizal fungi either
between root cells or within the cell wall.
❖ Vesicles are common in fungi, especially in the apical regions
and where ever wall synthesis is in progress.
❖ The apex of hyphae contains a large number of vesicles and is
termed Apical Vesicular Complex (AVC).
❖ They transport the products formed by the secretary action of
Golgi apparatus to the site where these products are to be
utilized.
K R MICRO NOTES 18
MICROTUBULES
❖ Discovered by transmission electron microscopy in the late 1950s.
❖ In filamentous fungi,microtubule is an essential component of tip growth
machinery that enables continuous and rapid growth.
❖ Composed of the protein tubulin which consist of a dimer composed of two
protein subunit.
❖ Microtubules are long, hollow cylinder -25nm in diameter
❖ Involved in the movement of organelles, nuclei and Golgi vesicles containing
cell wall precursor.
❖ Assist in the movement of chromosomes during mitosis and meiosis
❖ The destruction of cytoplasmic microtubules interferes with the transport of
secretory material to the cell periphery, which may inhibit the cell wall
❖ synthesis.
K R MICRO NOTES 19
Micro Bodies
It was first described by Frederick and commerce workers in 1975.
These organelles are round, oval, 1.5-2.0 I'm in diameter surrounded
by single unit membrane.
Their origin is unknown.
They may be identical to or may be the precursors of peroxisomes or
lysosomes, which contains either catalase or histolytic enzymes.
"Woronin bodies " named after M. S woronin, are generally spherical
and highly refractive bodies and are bound by unit membrane.
These are found associated with septal pores of discomycetes and
many deuteromycetous fungi
K R MICRO NOTES 20
GROWTH
❖Growth is defined as the irreversible constant
increase in the dry mass of an organism.
❖It is brought about by an increase in cell size or
number.
❖It is the fundamental characteristics of living
bodies accompanied by various metabolic
processes. (anabolic or catabolic)
❖Factors effecting growth : External factors - light,
temperature, water, nutrients; Internal factors -
hormones.
K R MICRO NOTES 21
OPTIMUM CONDITION FOR GROWTH
❖ Presence of water: 80–90% of the fungi is composed of water by mass, and
requires excess water for absorption due to the evaporation of internally
retent water.
❖ Presence of oxygen
❖ Neutral-acidic pH : Optimum pH 5.0
❖ Low-medium temperature: ranges between 1°C and 35°C, with optimum
growth at 25 °C.
K R MICRO NOTES 22
❖Growth in fungi can be seen by
❖ unicellular organization
❖ in form of hyphae
K R MICRO NOTES 23
UNICELLULAR ORGANIZATION
❖ Unicellular organization occur in some fungal
groups. The most widely known are the yeast.
❖ Budding takes place during favourable
condition.
❖ The protoplasm of vegetative cell swells up at
one side in the form of a bud.
❖ The nucleus undergoes mitotic division.
❖ Out of two nuclei formed by mitosis, one goes
to the bud and other one remains in the
mother.
❖ Bud enlarges and eventually cuts off from the
mother by partition wall and grows
individually.
❖ The size of the bud is always smaller than the
mother cell.
K R MICRO NOTES 24
❖ Sometimes due to rapid
division, large number of
buds develop without
being detached from one
another and persist in the
form of branched or
unbranched chain, called
pseudo-
mycelium.
K R MICRO NOTES 25
IN FORM OF HYPHAE
❖ Under favourable environmental conditions, fungal spores germinate and
form hyphae.
❖ The hypha may be roughly divided into three regions:
❖ (1) the apical zone about 5–10 micrometres in length,
❖ (2) the subapical region, extending about 40 micrometres back of the
apical zone, which is rich in cytoplasmic components, such as nuclei,
Golgi apparatus, ribosomes, Mitochondria, the Endoplasmic Reticulum,
and vesicles, but is devoid of Vaculoes.
❖ (3) the zone of vacuolation, which is characterized by the presence of
many vacuoles and the accumulation of Lipids.
K R MICRO NOTES 26
❖ Fungal hyphae extend continuously at their extreme tips.
❖ The rate of tip extension can be extremely rapid - up to 40
micrometres per minute.
❖ It is continuous movement of materials into the tip from older
regions of the hyphae.
❖ This unique mode of growth - apical growth - is the hallmark of
fungi, and it accounts for much of their environmental and
economic significance.
K R MICRO NOTES 27
MECHANISM OF APICAL GROWTH
K R MICRO NOTES 28
SPITZENKÖRPER
❖ The mature vegetative hyphae elongate by means of tip growth.
❖ The extreme tip of a growing hypha has very few organelles; instead,
it contains a body termed the Spitzenkörper.
❖ This consists of a cluster of small, membrane-bound vesicles
embedded in a meshwork of actin microfilaments.
❖ The Spitzenkörper is always present in growing tips, disappears
when growth stops, reappears when growth restarts.
K R MICRO NOTES 29
❖ A region within the centre of the
Spitzenkörper (the ‘core’) is largely
devoid of nuclei.
❖ Spitzenkörper is generally regarded
as a ‘vesicle supply centre’, which
regulates the initiation, maintenance,
and direction of hyphal growth.
K R MICRO NOTES 30
CYTOSKELETON
❖ There are two main cytoskeletal elements
in fungi: microtubules, actin
microfilaments.
❖ Microtubules and actin microfilaments
play a variety of roles:
❖ formation of spindles.
❖ allowing chromosome segregation during
nuclear division.
❖ nuclear positioning.
❖ providing long distance transport of
secretory vesicles to hyphal tips.
❖ Intracellular movement of organelles and
protein complexes.
K R MICRO NOTES 31
❖ The rate of hyphal extension might be controlled, and
bursting prevented, by the actin/spectrin cap
❖ The transport of secretory vesicles and other organelles
along cytoskeletal elements is driven by motor proteins
❖ Depolymerization of microtubules results in a disappearance
of the Spitzenkorper, termination or reduction of apical
growth and enzyme secretion.
❖ Actin depolymerization leads to uncontrolled tip extension
to form giant spheres.
❖ The integrity of the Spitzenkorper is maintained by an
interplay between actin and microtubule.
K R MICRO NOTES 32
SECRETORY PROCESS OF HYPHAL TIP GROWTH
K R MICRO NOTES 33
SYNTHESIS OF CELL WALL
K R MICRO NOTES 34
FUNGAL GROWTH PHASES
❖ From the time a spore or a hyphal fragment germinates to form a
colony to the time the fungus dies, there are a number of growth
phases.
❖ Although these phases have been determined under laboratory
conditions, it is possible that the same occur in nature.
❖ The unicellular organisms (Yeast) may present different phases :-
❖ 1.Lag phase 2. Log phase or exponential phase 3.Retardation phase
4.stationary phase .
K R MICRO NOTES 35
K R MICRO NOTES 36
Lag phase
❖ Once the growth conditions become favourable for the fungi to germinate, new
transport systems must be induced before growth starts.
❖ Thus growth starts slowly. This phase is referred to as the lag phase.
Exponential or log phase
❖ Hyphae branches are initiated
❖ The new hypha extends at a linear .
❖ The biomass of the growing fungus doubles per unit time.
❖ As long as the nutrients are in excess growth remains constant during the
exponential phase.
K R MICRO NOTES 37
Retardation Phase :
 After the end of the exponential phase the growth of the culture
ceases long before the nutrients in the medium where exhausted.
Stationary phase
❖ As soon as the nutrients are depleted or toxic metabolites are
produced growth slows down or is completely stopped.
❖ During the stationary phase, hyphal growth stops and, in some molds,
cell differentiation occurs, resulting in spore formation.
❖ During this process nutrients are transferred from the vegetative
mycelium to the developing spores.
❖ The spores are dispersed by air movement to other areas of the
building where they can start new mold growth once the conditions
K R MICRO NOTES 38
Different Phases of Growth In filamentous Fungi is due to
linear phase of growth
Here Usually exponential Phase is replaced by linear
phase of growth.
In linear Phase growth of fungi is limited to terminal
portion of the hyphae.
This phenomenon of terminal growth was studied in
Fusarium, Aspergillus, Pencillium, Rhizopus.
Three dimension growth can also be seen in standing
liquid cultures , Fungi usually grow as floating mats.
K R MICRO NOTES 39
GENERTION TIME
Generation time is the average time between two consecutive
generations in the lineages of a population.
When growing exponentially by binary fission, the increase in a fungal
population is by geometric progression. If we start with one cell, when
it divides, there are 2 cells in the first generation, 4 cells in the second
generation, 8 cells in the third generation, and so on. The generation
time is the time interval required for the cells (or population) to divide
Calculation of Generation Time
G (generation time) = (time, in minutes or hours)/n (number of
generations)
G = t/n
t = time interval in hours or minutes
B = number of cell at the beginning of a time interval
b = number of cell at the end of the time interval
n = number of generations (number of times the cell population
doubles during the time interval)
. K R MICRO NOTES 40
b = B x 2n
Solve for n:
Log b = log B + n log 2
n = log b – log B log 2
n = log b – log B 0.301
n = 3.3 log b/B
G = t/n
Solve for G
G = t . 3.3 log b/B
K R MICRO NOTES 41
MEASUREMENT OF FUNGAL GROWTH
❖ The following two methods used for measuring the growth
in fungi.
❖ The methods are:
❖ Linear Method (Agar Plate)
❖ Mycelial Dry Weight (Biomass)
K R MICRO NOTES 42
Linear Method
❖ Linear Growth means that the
fungus grows by the same amount
in each time.
❖ To measure the diameter of the
colony at two places - at right
angles to each other
❖ An average of the cross diameter
gives the growth of a fungus
❖ On solid medium the fungal
growth can be measured.
K R MICRO NOTES 43
Procedure
❖ Pour the media in sterile petriplate.
❖ Aseptically inoculate the culture
❖ Incubate the plates at 25°C (room temperature) for a week or 10
days.
❖ Measure the diameter of each colony at 2-3 places and take the
average.
❖ This measurement can be done after 24, 48, 72, 96, 120 and 144
hours.
❖ Record the measurements.
❖ plot a graph with time against diameter of colony.
❖ A growth curve is obtained.
K R MICRO NOTES 44
Mycelial Dry Weight (Biomass)
❖ On liquid medium the mycelial growth can be measured.
❖ Determined by inoculating cultures into broth, followed by
filtering of mycelium, drying at 105°C for 48 hours to a constant
weight and weighing the mycelium.
K R MICRO NOTES 45
Procedure
❖ Pour the media in sterile petriplate.
❖ Aseptically inoculate the culture
❖ Incubate the plates at 25°C (room temperature) for a week or
10 days.
❖ Filtered the content through a pre weighed filter paper.
❖ Dry the filter paper in an oven for 48 hours at 105°C.
❖ Reweigh the filter papers with dry mycelium, subtract the
weight of filter paper .
❖ Prepare growth curve with time (hours) against weight of
mycelium.
K R MICRO NOTES 46
REFERENCE
❖An Introduction to Mycology –
--R.S Meherotra & K.R. Aneja.
❖Introduction to Fungi- Webster.
❖ Introductory Mycology – D P Tripathi
K R MICRO NOTES 47
K R MICRO NOTES 48

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ULTRA STRUCTURE OF FUNGAL CELL AND GROWTH

  • 1. ULTRA STRUCTURE OF FUNGAL CELL AND GROWTH K R MICRO NOTES 1
  • 2. INTRODUCTION ❖ FUNGI is the plural for the word FUNGUS which is derived from the latin word FUNGOUR, which means to flourish. ❖ Fungi can be defined as eukaryotic, spore bearing, achlorophyllous organisms and Thallophytic plants that may reproduce sexually or asexually and whose filamentous, branched and somatic structures are typically surrounded by cell walls containing chitin, cellulose, or combination of both. ❖ The branch of biology which deals with the study of fungi is called mycology (Mykes = Mushroom or fungi, logos = Discourse) K R MICRO NOTES 2
  • 3. ❖ They are ubiquitous in terrestrial and fresh water habitats, less in the marine environment. ❖ They are cosmopolitan in distribution ❖ Characteristically, they are saprophytic, parasitic, symbiotic or hyper parasitic in nature. ❖ They are also used for preparation of different industrial substances including antibiotics, enzymes and acids etc.. K R MICRO NOTES 3
  • 5. Cross-section view of a typical fungal cell K R MICRO NOTES 5
  • 6. CELL WALL  The main identifying characteristics of fungi is the make up of their cell walls.  The composition of the fungal cell wall is rather variable.  It gives strength and shape to fungi.  Iit provides protection for the protoplasm from UV RAYS(presence of melanin)  Glucan and Chitin are components of the primary wall, proteins are the components on the secondary cell.  Ability to resist Lysis by organic solvents such as enzymes, toxins and osmotic integrity.  They have ability to bind with metal ions.  Except slime moulds (Myxomycetes) ,the fungal cell consist of a rigid cell wall and cell organelles. 6
  • 7.  The cell wall of Ascomycotina and Basidiomicotina contains chitin (β 1,4 N- acetylglucosamine ).  In the Zygomycotina, the chitin fibres are modified to produce poly-β-(1,4)glucosamine, which is called chitosan.  The cell walls of oomycetes contain cellulose and lack chitin. K R MICRO NOTES 7
  • 8. CELL MEMBRANE ❖ In fungal cells, the living protoplast is enclosed in a cell membrane,also called the plasma membrane or plasmalemma. ❖ It is delicate, extremely thin semipermeable membrane. ❖ The principal components of plasmalemma are proteins and lipids. ❖ At the surface of plasmalemma ,some membrane structures known as lomasomes and plasmalomosomes have been reported. ❖ Glucose residues, Glucosamine, sterols(ergosterol), Mannose are present. K R MICRO NOTES 8
  • 9. CYTOPLASM  Within the plasma membrane ,is the colourless cytoplasm in which sap-filled vacuoles may occur.  Immersed in the cytoplasm are structures known as the organelles and inclusions.  The organelles are living structures,each with a specific function.The inclusions are dead,have no specific function and thus are not essential to cell survival.  Among the cell organelles are included the E.R,mitochondria,ribosomes,Golgi apparatus and vacuoles.  Examples of inclusions are the stored foods( glycogen,oil drops) pigments and secretory granules. K R MICRO NOTES 9
  • 10. NUCLEUS ❖ The cytoplasm contains one, two or more globose or spherical nuclei ❖ It measures up to 1-3 µm in diameter. ❖ Structurally the nucleus consists of : ❖ A central dense body(nucleolus). ❖ Chromatin strands. ❖ The whole structures surrounded by a definite nuclear membrane. ❖ Under the electron microscope, nuclear membrane is seen to consist of 2 unit membranes - inner and outer layers of electron dense material. ❖ It has pores, at certain points and the membrane is continuous with ER. K R MICRO NOTES 10
  • 11. ENDOPLASMIC RETICULUM ❖ Presence of endoplasmic reticulum in fungal cytoplasm is observed through electron microscope. ❖ It is made up of flattened sacs of membrane- cisternae. ❖ It is composed of a system of membranes or micro tubular structures with small granules (ribosomes) ❖ In many fungi, the E.R is highly vesicular. ❖ It is loose and irregular as compared with cells of green plants. K R MICRO NOTES 11
  • 12. RIBOSOMES ❖ Ribosomes is found on the ER , others free floating in the cytoplasm. ❖ They are proteinaceous bodies with high RNA content. ❖ They are concerned with protein synthesis . ❖ They aggregate to form polyribosomes (or polysomes) K R MICRO NOTES 12
  • 13. GOLGI BODIES( DICTYOSOMES) ❖ Moore and Muhlethaler in 1963 reported 3 flattened sacs in Saccharomyces cells. ❖ Golgi Bodies or dictyosomes are found comparatively rarely in fungi (except oomycetes). ❖ Not organized as stacks of flattened cisternae . ❖ Instead, the Golgi bodies of fungi appear as single tubular, cisternae that vary in shape from cup-like to planar bodies. ❖ functionally equivalent to the stacked Golgi bodies. ❖ Major function is to process and package macromolecules (proteins) and transportation of lipids around the cell. K R MICRO NOTES 13
  • 14. K R MICRO NOTES 14
  • 15. MITOCHONDRIA ❖ Richard Altmann , in 1890, established cell organelles and called them “bioblasts”. Carl Benda coined the term “mitochondria” in 1898. ❖ The cytoplasm contains small, usually spherical bodies known as the mitochondria. ❖ Each mitochondrion is enveloped by a double membrane. ❖ The inner membrane is infolded to form the cristae which are in the form of parallel flat plates. ❖ The mitochondria function as the power house of the cell. ❖ Mitochondria has its own machinery for transcription and translation of organelle specific DNA. K R MICRO NOTES 15
  • 16. VACUOLES ❖ Vacuoles are essential for cell function in fungi. Fungi are characterized by the presence of spherical to tubular vacuoles. Vacuoles are found in the old cells of hyphae. The end of hyphal tip of young hyphae lacks vacuole. ❖ Vacuoles are surrounded by a membrane known as tonoplast. ❖ The function of the vacuoles is to provide the turgor needed for cell growth and maintenance of cell shape. ❖ Besides osmotic function,it stores reserve materials(Volutin- polymetsphosphate ; in yeasts), pigments , amino acids and hydrolases. K R MICRO NOTES 16
  • 17. LYSOSOMES ❖ Thornton (1968) described them as “ Autophagic vesicles”. ❖ They have been described only in Botrytis cinerea and Phycomyces. ❖ They are thought to be derived from Golgi cisternae. ❖ Simple lysosomes have a diameter of 400nm and are bound by a unit membrane. K R MICRO NOTES 17
  • 18. VESICLES ❖ The term vesicle is used for any cell or organ that is inflated by the stuff that is used to store. (swollen end cells) ❖ This are generally formed by Endomycorrhizal fungi either between root cells or within the cell wall. ❖ Vesicles are common in fungi, especially in the apical regions and where ever wall synthesis is in progress. ❖ The apex of hyphae contains a large number of vesicles and is termed Apical Vesicular Complex (AVC). ❖ They transport the products formed by the secretary action of Golgi apparatus to the site where these products are to be utilized. K R MICRO NOTES 18
  • 19. MICROTUBULES ❖ Discovered by transmission electron microscopy in the late 1950s. ❖ In filamentous fungi,microtubule is an essential component of tip growth machinery that enables continuous and rapid growth. ❖ Composed of the protein tubulin which consist of a dimer composed of two protein subunit. ❖ Microtubules are long, hollow cylinder -25nm in diameter ❖ Involved in the movement of organelles, nuclei and Golgi vesicles containing cell wall precursor. ❖ Assist in the movement of chromosomes during mitosis and meiosis ❖ The destruction of cytoplasmic microtubules interferes with the transport of secretory material to the cell periphery, which may inhibit the cell wall ❖ synthesis. K R MICRO NOTES 19
  • 20. Micro Bodies It was first described by Frederick and commerce workers in 1975. These organelles are round, oval, 1.5-2.0 I'm in diameter surrounded by single unit membrane. Their origin is unknown. They may be identical to or may be the precursors of peroxisomes or lysosomes, which contains either catalase or histolytic enzymes. "Woronin bodies " named after M. S woronin, are generally spherical and highly refractive bodies and are bound by unit membrane. These are found associated with septal pores of discomycetes and many deuteromycetous fungi K R MICRO NOTES 20
  • 21. GROWTH ❖Growth is defined as the irreversible constant increase in the dry mass of an organism. ❖It is brought about by an increase in cell size or number. ❖It is the fundamental characteristics of living bodies accompanied by various metabolic processes. (anabolic or catabolic) ❖Factors effecting growth : External factors - light, temperature, water, nutrients; Internal factors - hormones. K R MICRO NOTES 21
  • 22. OPTIMUM CONDITION FOR GROWTH ❖ Presence of water: 80–90% of the fungi is composed of water by mass, and requires excess water for absorption due to the evaporation of internally retent water. ❖ Presence of oxygen ❖ Neutral-acidic pH : Optimum pH 5.0 ❖ Low-medium temperature: ranges between 1°C and 35°C, with optimum growth at 25 °C. K R MICRO NOTES 22
  • 23. ❖Growth in fungi can be seen by ❖ unicellular organization ❖ in form of hyphae K R MICRO NOTES 23
  • 24. UNICELLULAR ORGANIZATION ❖ Unicellular organization occur in some fungal groups. The most widely known are the yeast. ❖ Budding takes place during favourable condition. ❖ The protoplasm of vegetative cell swells up at one side in the form of a bud. ❖ The nucleus undergoes mitotic division. ❖ Out of two nuclei formed by mitosis, one goes to the bud and other one remains in the mother. ❖ Bud enlarges and eventually cuts off from the mother by partition wall and grows individually. ❖ The size of the bud is always smaller than the mother cell. K R MICRO NOTES 24
  • 25. ❖ Sometimes due to rapid division, large number of buds develop without being detached from one another and persist in the form of branched or unbranched chain, called pseudo- mycelium. K R MICRO NOTES 25
  • 26. IN FORM OF HYPHAE ❖ Under favourable environmental conditions, fungal spores germinate and form hyphae. ❖ The hypha may be roughly divided into three regions: ❖ (1) the apical zone about 5–10 micrometres in length, ❖ (2) the subapical region, extending about 40 micrometres back of the apical zone, which is rich in cytoplasmic components, such as nuclei, Golgi apparatus, ribosomes, Mitochondria, the Endoplasmic Reticulum, and vesicles, but is devoid of Vaculoes. ❖ (3) the zone of vacuolation, which is characterized by the presence of many vacuoles and the accumulation of Lipids. K R MICRO NOTES 26
  • 27. ❖ Fungal hyphae extend continuously at their extreme tips. ❖ The rate of tip extension can be extremely rapid - up to 40 micrometres per minute. ❖ It is continuous movement of materials into the tip from older regions of the hyphae. ❖ This unique mode of growth - apical growth - is the hallmark of fungi, and it accounts for much of their environmental and economic significance. K R MICRO NOTES 27
  • 28. MECHANISM OF APICAL GROWTH K R MICRO NOTES 28
  • 29. SPITZENKÖRPER ❖ The mature vegetative hyphae elongate by means of tip growth. ❖ The extreme tip of a growing hypha has very few organelles; instead, it contains a body termed the Spitzenkörper. ❖ This consists of a cluster of small, membrane-bound vesicles embedded in a meshwork of actin microfilaments. ❖ The Spitzenkörper is always present in growing tips, disappears when growth stops, reappears when growth restarts. K R MICRO NOTES 29
  • 30. ❖ A region within the centre of the Spitzenkörper (the ‘core’) is largely devoid of nuclei. ❖ Spitzenkörper is generally regarded as a ‘vesicle supply centre’, which regulates the initiation, maintenance, and direction of hyphal growth. K R MICRO NOTES 30
  • 31. CYTOSKELETON ❖ There are two main cytoskeletal elements in fungi: microtubules, actin microfilaments. ❖ Microtubules and actin microfilaments play a variety of roles: ❖ formation of spindles. ❖ allowing chromosome segregation during nuclear division. ❖ nuclear positioning. ❖ providing long distance transport of secretory vesicles to hyphal tips. ❖ Intracellular movement of organelles and protein complexes. K R MICRO NOTES 31
  • 32. ❖ The rate of hyphal extension might be controlled, and bursting prevented, by the actin/spectrin cap ❖ The transport of secretory vesicles and other organelles along cytoskeletal elements is driven by motor proteins ❖ Depolymerization of microtubules results in a disappearance of the Spitzenkorper, termination or reduction of apical growth and enzyme secretion. ❖ Actin depolymerization leads to uncontrolled tip extension to form giant spheres. ❖ The integrity of the Spitzenkorper is maintained by an interplay between actin and microtubule. K R MICRO NOTES 32
  • 33. SECRETORY PROCESS OF HYPHAL TIP GROWTH K R MICRO NOTES 33
  • 34. SYNTHESIS OF CELL WALL K R MICRO NOTES 34
  • 35. FUNGAL GROWTH PHASES ❖ From the time a spore or a hyphal fragment germinates to form a colony to the time the fungus dies, there are a number of growth phases. ❖ Although these phases have been determined under laboratory conditions, it is possible that the same occur in nature. ❖ The unicellular organisms (Yeast) may present different phases :- ❖ 1.Lag phase 2. Log phase or exponential phase 3.Retardation phase 4.stationary phase . K R MICRO NOTES 35
  • 36. K R MICRO NOTES 36
  • 37. Lag phase ❖ Once the growth conditions become favourable for the fungi to germinate, new transport systems must be induced before growth starts. ❖ Thus growth starts slowly. This phase is referred to as the lag phase. Exponential or log phase ❖ Hyphae branches are initiated ❖ The new hypha extends at a linear . ❖ The biomass of the growing fungus doubles per unit time. ❖ As long as the nutrients are in excess growth remains constant during the exponential phase. K R MICRO NOTES 37
  • 38. Retardation Phase :  After the end of the exponential phase the growth of the culture ceases long before the nutrients in the medium where exhausted. Stationary phase ❖ As soon as the nutrients are depleted or toxic metabolites are produced growth slows down or is completely stopped. ❖ During the stationary phase, hyphal growth stops and, in some molds, cell differentiation occurs, resulting in spore formation. ❖ During this process nutrients are transferred from the vegetative mycelium to the developing spores. ❖ The spores are dispersed by air movement to other areas of the building where they can start new mold growth once the conditions K R MICRO NOTES 38
  • 39. Different Phases of Growth In filamentous Fungi is due to linear phase of growth Here Usually exponential Phase is replaced by linear phase of growth. In linear Phase growth of fungi is limited to terminal portion of the hyphae. This phenomenon of terminal growth was studied in Fusarium, Aspergillus, Pencillium, Rhizopus. Three dimension growth can also be seen in standing liquid cultures , Fungi usually grow as floating mats. K R MICRO NOTES 39
  • 40. GENERTION TIME Generation time is the average time between two consecutive generations in the lineages of a population. When growing exponentially by binary fission, the increase in a fungal population is by geometric progression. If we start with one cell, when it divides, there are 2 cells in the first generation, 4 cells in the second generation, 8 cells in the third generation, and so on. The generation time is the time interval required for the cells (or population) to divide Calculation of Generation Time G (generation time) = (time, in minutes or hours)/n (number of generations) G = t/n t = time interval in hours or minutes B = number of cell at the beginning of a time interval b = number of cell at the end of the time interval n = number of generations (number of times the cell population doubles during the time interval) . K R MICRO NOTES 40
  • 41. b = B x 2n Solve for n: Log b = log B + n log 2 n = log b – log B log 2 n = log b – log B 0.301 n = 3.3 log b/B G = t/n Solve for G G = t . 3.3 log b/B K R MICRO NOTES 41
  • 42. MEASUREMENT OF FUNGAL GROWTH ❖ The following two methods used for measuring the growth in fungi. ❖ The methods are: ❖ Linear Method (Agar Plate) ❖ Mycelial Dry Weight (Biomass) K R MICRO NOTES 42
  • 43. Linear Method ❖ Linear Growth means that the fungus grows by the same amount in each time. ❖ To measure the diameter of the colony at two places - at right angles to each other ❖ An average of the cross diameter gives the growth of a fungus ❖ On solid medium the fungal growth can be measured. K R MICRO NOTES 43
  • 44. Procedure ❖ Pour the media in sterile petriplate. ❖ Aseptically inoculate the culture ❖ Incubate the plates at 25°C (room temperature) for a week or 10 days. ❖ Measure the diameter of each colony at 2-3 places and take the average. ❖ This measurement can be done after 24, 48, 72, 96, 120 and 144 hours. ❖ Record the measurements. ❖ plot a graph with time against diameter of colony. ❖ A growth curve is obtained. K R MICRO NOTES 44
  • 45. Mycelial Dry Weight (Biomass) ❖ On liquid medium the mycelial growth can be measured. ❖ Determined by inoculating cultures into broth, followed by filtering of mycelium, drying at 105°C for 48 hours to a constant weight and weighing the mycelium. K R MICRO NOTES 45
  • 46. Procedure ❖ Pour the media in sterile petriplate. ❖ Aseptically inoculate the culture ❖ Incubate the plates at 25°C (room temperature) for a week or 10 days. ❖ Filtered the content through a pre weighed filter paper. ❖ Dry the filter paper in an oven for 48 hours at 105°C. ❖ Reweigh the filter papers with dry mycelium, subtract the weight of filter paper . ❖ Prepare growth curve with time (hours) against weight of mycelium. K R MICRO NOTES 46
  • 47. REFERENCE ❖An Introduction to Mycology – --R.S Meherotra & K.R. Aneja. ❖Introduction to Fungi- Webster. ❖ Introductory Mycology – D P Tripathi K R MICRO NOTES 47
  • 48. K R MICRO NOTES 48