Rhizopus Stolonifer: Life Cycle, Habitat, Nutrition, Disease, Importance.

Kingdom	Fungi
Phylum	`Mucoromycota`
Order	`Mucorales`
Family	Mucoraceae
Genus	Rhizopus
Species	R. stolonifer
Binomial name	Rhizopus stolonifer

Rhizopus Stolonifer Morphology

In 1818, a German scientist Christian Gottfried Ehrenberg first discovered this fungus as Rhizopus nigricans. In 1902, a French mycologist J. P. Vuillemin changed the name to Rhizopus stolonifer.

Rhizopus stolonifer also termed as black bread mold.
They are mainly grow on bread and soft fruits.

It contains white cottony thallus with much-branched mycelium.
It is a Filamentous mold and member of Zygomycete.
Rhizopus stolonifer is a Saprophytic which means it consumes dead organic matter.

Some of them also show Parasitic characteristics, they get all nutrients from the substrate on which it lands.
In carbon cycle Rhizopus stolonifer play an important role as a decomposer in the soil.
Mainly found as mycelia made up of hyphae that lack cross walls or septa.

It is a coenocytic organism because it has a multinucleate cell that is enclosed by a chitinous one cell wall.
The Mycelium is divided into two parts such as nodes and internodes. The nodal portion shows much-branched rhizoid produces descending, inside the substratum for safety and consumption of food.
It forms Sporangiophores, which is up to 2.5 mm long and about 20 μm in diameter.

The shape of spores is varies based on the available nutrients, it can be ovate, polygonal or angular shape.
The optimal temperature of Rhizopus stolonifer varies between 25 and 30 °C. The thermal death point is 60 °C.
It can grow in acidic environments at pH 2.2. The pH range sometimes varies from 2.2 to 9.6.

The internodal region termed as stolon, when it reaches the substratum develops the nodal region.
R. stolonife mainly grows in indoor environments.
It also an opportunistic agent which means it can cause disease in people with a impaired immunity.

Habitat of Rhizopus stolonifer

Rhizopus stolonifer is distributed worldwide. It mainly grows on mouldy materials.
They can be found in warm and dry environments such as soil, fresh decaying litter, wild bird nests, and children’s sand boxes.
Mostly exist in moist environments.

In the laboratory, they grow on ammonium salts or amino compounds containing medium. But it does not grow on Czapek’s agar because it cannot use nitrogen in the form of nitrate.

Habitat of Rhizopus stolonifer — Image Source: www.britannica.com

Nutrition of Rhizopus stolonifer

When it reaches its substrate, first it started to spread all over the surface of the substrate, and then it penetrates its hyphae within the substrate to absorb nutrients.

Disease caused by Rhizopus stolonifer

Rhizopus stolonifer is responsible for ripe fruits, such as strawberries, melon, and peach, mainly those contain wounds and higher sugar content. During germination, it produces esterases, including cutinase which enable the penetration of fungus into the plant cell wall.

Prevention of Rhizopus stolonifer

Some species of Syncephalis can decrease the rate of asexual reproduction in R. stolonifer as a result it can delay or even prevent the post-harvest disease.
An anti-fungal complex, Fengycin is used to inhibit the fungal cell via necrosis and apoptosis.
Sweet potatoes can be stored with Sodium orthophenyl phenol (Stopmold B) and dichloran (Botran W) to prevent the infection.

Importance of Rhizopus stolonifer

It used for the production of ethyl alcohol which is a most important fermentation product.
Commercially it used to produce fumaric acid and lactic acid of high purity.

Reproduction or Life cycle of Rhizopus stolonifer

Rhizopus stolonifer is reproduced by Fragmentation, Asexual method and Sexual method. The Asexual reproduction in Rhizopus stolonifer is followed by Sporangiospore formation and chalmydospore formation, while sexual reproduction is followed by gamentagial copulation.

Fragmentation

The fragmentation reproduction in Rhizopus stolonifer is accomplished by the disjoining of hyphae which gives rise to a new organism.

Culture medium Definition, Preparation, Classification

The nutrient preparation on or in which a culture (microorganism) is grown in the laboratory is known as culture medium or culture media.

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Culture medium Definition, Preparation, Classification

Asexual reproduction of Rhizopus stolonifer

The favorable environmental condition triggers the Asexual reproduction in Rhizopus. During asexual reproduction, the aerial hyphae is produced from the internode and rise to a definite height. The nuclei and cytoplasm shift deeper and deeper towards the apical side, consequently, the apex of the aerial hyphae puffs up.

The swollen portion is expanded and develops into a huge round sporangium. Then the Sporangium separates into two regions such as multinucleated sporoplasm and vaculated columellaplasm.

Nucleus within the sporoplasm divides immediately, and all nuclei find some cytoplasm and convert into spongiospore. After certain development columella deflated releasing sporangiospores in the atmosphere.

Now, the Sporangiospore associated with the substratum and germinates to give rise mycelium. In presence of the adverse conditions, septum synthesis occurs within the mycelium and each intercalary mycelium forms a thick resting spore called chlamydospore.

Sexual reproduction of Rhizopus stolonifer

The Sexual reproduction of Rhizopus stolonifer occurs in presence of unfavorable conditions by means of gametangial copulation. Most of the Rhizopus are heterothallic in nature. When two mycelium of different strain come in contact, each mycelium forms a small outgrowth, termed progametangia.

The apical area of the two progametangia aggregates and the cytoplasm of each progametangium pushes deeper and deeper towards the apical area which swells up with compact protoplasm. The apical region is called gametangia while the basal region is called as suspensor.

The protoplasm in gametangia fuses and develops a resting spore known as Zygospore. On returning favorable condition, spore wall break and develops germ tube which extends to form promycelium. The Promycellium contain two region such as germsporangiophore and germsporangium.

The nucleus in germsporanium is separated by meiosis developing haploid nuclei, which gather cytoplasm and acts as spores. The haploid spore is discharged and grows to give rise a new mycelium.