Rhizopus is a type of fungus belonging to the class Zygomycetes. It reproduces through both asexual and sexual means. Asexually, it produces sporangiospores or chlamydospores which germinate into new fungal thalli under suitable conditions. Sexually, conjugation between opposite mating types leads to the formation of thick-walled zygospores which act as resting structures until germinating into new thalli. Rhizopus has a coenocytic mycelium and produces sporangia bearing sporangiospores aerially from sporangiophores.

1. Rhizopus
Presented by Irfan M

2. What is Rhizopus ?
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▪ Rhizopus is a type of fungus which belongs to the
class Zygomycetes because of the fact that it produces zygospore in its
sexual reproductive phase. It also refers to bread, black or pin mould.
▪ There are around 8-10 known species of Rhizopus.
▪ The name Rhizopus was first named by Ehrenb in 1820.

3. Classification
▪ Kingdom : Fungi
▪ Division : Mycota
▪ Sub-division: Eumycotina
▪ Class : Zygomycetes
▪ Order : Mucorales
▪ Family : Mucoraceae
▪ Genus : Rhizopus 3

4. Features of Rhizopus
 The mode of nutrition is saprophytic and parasitic in Rhizopus
where a majority of them are saprophytic and few are parasitic
viz. R.artocarp, R.arrhizus etc.
 In Rhizopus, the mycelium is coenocytic, tubular,
multinucleated, vacuolated and consist of cytoplasmic
materials like Golgi body, mitochondria etc.
 The reserve food material is in the form of glycogen and oil
droplets.

5.  A cell wall of the thallus is non-cellulose and made of chitin.
 The hyphae of Rhizopus differentiates into three distinctive
parts namely stolon (intermodal region), rhizoids (nodal region)
and sporangiophores.
 For the growth of Rhizopus, the most important factor
is moisture or water availability.
 These are the opportunistic fungi which can commonly cause
“Zygomycosis or Mucormycosis”.

6. Structure of Rhizopus
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1. Hyphae
Stolon
Rhizoids
2. Cell- wall
3. The protoplasm
4. Columella
5. Sporangium
6. Sporangiospores

7. ▪ Hyphae: Rhizopus consists of two kinds of hyphae
namely vegetative and reproductive hyphae. Vegetative
hyphae differentiate into two types namely Stolon and rhizoids
Stolon: It is the intermodal region which also refers to Runner.
A stolon is the aerial hyphae which grow horizontally and is
found attached to the substratum. It is aseptate, branched and
lacks cross walls.
Rhizoids: It is the nodal region which forms when the stolon
touches the surface of the substratum. Rhizoid is the much-
branched structure that forms under the substratum. Its main
function is to invade all the nutrients from the substratum. 7

8. Reproductive hyphae consist of sporangiophores which grow
vertically from the stolon. Sporangiophores are unbranched,
elongated, columellate and give rise to the reproductive
structures refers to sporangiospores.
▪ Cell- wall: The cell wall of hyphae is composed of chitin
chitosan, lipids, proteins etc.
▪ The protoplasm: It consists of many nuclei, mitochondria,
endoplasmic reticulum and other cytoplasmic inclusions like
the ribosome, oil droplets, vacuoles etc.
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9. ▪ Columella: It arises from the sporangiophore which is generally
dome or umbrella-shaped. The surface of columella can be
smooth or rough. The columella is hygroscopic in nature which
the main function is water absorption.
▪ Sporangium: It connects with the columella and a long
sporangiophore. The shape of the sporangium is spherical or
globose in shape. It carries the reproductive structures refers as
sporangiospores. The size of the sporangium is 0.2mm.
▪ Sporangiospores: These are the asexual spores which are globose
to ovoid and unicellular. The colour of sporangiospores is hyaline
to brown. 9

10. General cultural characteristics
 Growth: The growth of
mycelium is very fast- growing.
 Appearance: Dense cottony
colonies
 Colour: The colour of
mycelium is generally white
and after sporulation turns
grey or golden brown

11. Reproduction in
Rhizopus
It reproduces by vegetative, asexual and sexual methods
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12. “Sometimes the thallus of the Rhizopus breaks accidentally or
some other factors into few fragments where each fragment give
rise to a new thallus on favourable conditions.
Vegetative reproduction
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13. The asexual reproduction can take place through both sporangiospores and chlamydospores.
Asexual reproduction
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Asexual reproduction
through sporangiospores
1. First, the vegetative hypha grows to form sporangiophore
that is long and slender.
2. Then the sporangiophore develops and enlarges at the apical
region to form columella which is of variable shape and size.

14. 14

15. 3. This columella gives rise to the large, round sporangium by pushing
cytoplasmic material to the peripheral wall.
4. After that, differentiation of sporangia takes place wherein between
sporangia and columella, spore sac is present which carries the
sporangiospores. The structure of Sporangiospores is oval, unicellular,
multinucleate and non-motile.
5. These sporangiospores multiply their number in the spore sac and in
extreme conditions, it ruptures the sporangial wall and releases out of the
wall.
6. In the environment, the sporangiospores remains in a dormant state or in a
resting state.
7. When favourable conditions return, these sporangiospores form germ tube
and undergo germination to form a vegetative hypha.

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Asexual reproduction
through chlamydospores

17. 1. During unfavourable condition like insufficient food
material and water, the protoplasm is surrounded by
a thick and nutrient-rich wall.
2. This chlamydospore then detaches from the
vegetative hyphae and remains in the resting phase.
3. When this chlamydospore gets moisture then it
forms a germ tube which then germinates into a
new thallus.

18. In Rhizopus, the sexual reproduction occurs by the method of “Gametangial conjugation”.
Sexual reproduction
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19. 1. First, the (+) and (-) thallus comes in contact with each other.
2. Then conjugation occurs between the positive and negative thalli
by the means of outgrowth developed by positive and negative
thalli.
3. The septum develops between the progametangium and
plasmogamy occurs that results in the formation of
“Coenogametes”.
4. Then karyogamy occurs by which the gametes of both the (+)
and (-) thallus fuse with each other to form “Zygote”.

20. 5. The zygote undergoes the maturation phase and surrounds by
a thick-walled structure called “Zygospore” which covers by
an outer layer and inner layer.
6. The zygospore undergoes a resting phase for some time. On
favourable conditions, zygospore forms germ tube and
germinates by forming a new vegetative body.