Aspergillus is commonly found in soil, with a saprophytic mode of nutrition, obtaining its nutrients from dead and decaying matter.The saprophytic nature of Aspergillus spp means they fully depend on environmental materials, which allows them to produce enzymes such as amylase that breaks down compounds into simple products that can be absorbed by the vegetative hyphae. food materials for utilization during reproduction and growth.
3. OCCURRENCE
Saprophytic fungus.
There are 200 species of Aspergillus.
Grows on decaying vegetable.
On fatty media such as butter and ghee.
On starchy media such as bread and rice.
On preserved food such as jams and jellies.
Also found on rotting oranges and other fruits.
4. APPEARANCE
Greenish and Smoky Patches along with Mucor,
Rhizopus & Penicillium on moist bread.
Other common shades are Yellow, Black, and Blue.
Mostly appear in the conodial stage
(imperfect stage).
Very few produce cleistothecia (perfect stage).
5. Cultural Characteristics
• Cottony appearance; initially white to yellow
and then turning black The reverse is white to
yellow.
• Potato dextrose agar at 25°C is initially white,
which quickly becomes black with conidial
production. The reverse is pale yellow and
growth may produce radial fissures in the agar.
• Malt Extract Agar – an incubation for 7 days
at 25ºC and 37ºC producing slightly brown
colonies smooth-walled colonies of conidia.
• Czapek Yeast Agar – after 5 days of
incubation at 25ºC and 37ºC, they produce
black colonies with wooly smooth-walled
colonies of conidia.
6. MYCELIUM
Well developed structures.
Made up of interwoven mass, branched and
septate hyphae.
Hyphae are branched and form mat on the
substratum.
Some of the hyphae lie superficially upon the
substratum and other penetrate deeply to
absorb food and for mycelium.
11. Length of conidiophores is around 2.5mm.
Swells at the tip and form globose called
vesicle.
Lumen of vesicle is continuous with upper
part of conidiopores.
From the surface of vesicle tubular cells grows
outwords called strigmata or phialides.
Phialides cover the whole surface of
vesicle.
12. DEVELOPMENT OF STERIGMETA/
PHIALIDES
By dissolution of cell wall material thin
tubular area formed.
Cytoplasm, nucleus, mitochondria and other
organelles migrate from vesicle to sterigmata.
In maturity stage sterigmata cut off from
vesicle from basal septum.
13. ABSTRICTIONS OF CONIDIA
Sterigmata are uninucleate
Nucleus divide by mitosis to form two
daughter nuclei
From two one migrates to tip of the sterigmata to form
first conidium
First conidium is cut off by basal septum at the
sterigmata apex.
By fragmentation fungus produce asexual spores
known as conidia
14. Later develop second
conidium in same manner.
This series of events
repeated.
Thus sterigmata continue to
grow conidia one below to
another.
Consequently chain of
conidia is formed at the tip of
the sterigmata.
The youngest is at the base
and oldest is at the top.
15. Two advantages
1. Dispersel of mature conidia in the air
2. Proper nourishment of young conidia
Conidia are black, green, brown, blue or yellow in
color according to their species
Conidial wall is thick consist of two layers outer
epispore and inner endospore
On falling of suitable substratum each
conidium germinates
First produce germ tube which grows into
mycelium
16.
17. SEXUAL REPRODUCTION
• Sexual reproduction is rare.
• Female sex organ is called
ascogonium or archicarp.
• Male sex organ is called pollonidium or
anthridium.
18. ASCOGONIUM (FEMALE SEX ORGAN)
Small, coiled septate
branch.
Terminal segment is
longest and single celled
called trigogyne contain
20 nuclei.
Trigogyne function as a
receptive part of female
sex organ.
19. ANTHREDIUM (MALE SEX ORGAN
Male branch grows beside the ascogonium
from the same hyphae.
Anthredium is multi nucleate.
20. PLASMOGAMY
Fusion of ascogonium and anthredium.
Tip of anthredium fuse with trochogyne.
Then intervening wall is dissolved.
Content of anthredium pass into the
trochogyne.
Here haplophase ends.
Male nuclei pair with female nuclei.
Each pair is called dikaryon and phase is called
dikaryophase.
21. The wall of asci is dissolved.
Ascopores are released into
cleistothesium.
Then wall of cleistothesium decays to
released ascopores into atmosphere.
Each ascopores germinate to form
mycelium.
25. ECONOMIC IMPORTANCE
44 species are reported in India.
Aspergillus oryzae is utilized to make alcohol.
Aspergillus niger is utilized in production of citric
acid and other organic acid.
Some species are the source of antibiotics.
Culture of A.niger and A.oryzae yield awide range
of enzymes.
Which are used for industrial
fermentation.
26. Decay tobacco and cigar.
Spoils nuts, bread and other food stuffs.
In humid atmosphere it grows on leather and
fabrics.
Sometimes produce poisonous substance called
mycotoxins.
Aspergillus Cause number of disease called
aspergilloses.
Eg. In human ear cause otomycosis.
