They can be found in regions that are moist or humid. They can be found on organic objects such as vegetables, fruits, bread, jams, and jellies, among other things. Multinucleated coenocytic hyphae are seen in the vegetative structure, which is also found in the fruiting body. They are employed in the production of a variety of chemicals and alcoholic beverages. Some rhizopus species cause plant illnesses and can also infect humans, a condition called mucormycosis, if they are exposed to the right conditions.
Classification and Illustrations
Rhizopus is a genus that belongs to the Zygomycota subphylum. The generation of zygospores during sexual reproduction distinguishes them from other species.
They are also referred to as black bread moulds, pin moulds, and other names.
Rhizopus
Rhizopus species that are commonly encountered include:
- Rhizopus stolonifer is a type of bread mould that is also known as black bread mould. Chemicals such as cortisone, fumaric acid, and other similar substances are commercially produced using this method. It is the cause of fruit rot disease.
- Rhizopus oryzae is a plant that produces alcoholic beverages.
- Rhizopus microsporus is a type of bacteria that is used to produce fermented soybean products.
Structure of the Rhizopus
- They are fungus that grow quickly and have a cottony texture to them.
- Rhizopus’s body is made up of a network of branching mycelium. sporangiophores are hyphae that are found in the mycelium, which is coenocytic and consisting of three types of hyphae: the stolon, rhizoids, and sporangiophores.
- Stolon is the internodal region; it is aerial, forms an arch, and touches the substratum, resulting in the formation of the nodal zone.
- Rhizoids are generated at nodes where the stolon comes into contact with the substratum. They are branching and serve to anchor the mycelium to the substratum as well as absorb nutrients.
- The aerial and reproductive mycelia are represented by the term sporangiophores. They are branching and consist of sporangiospores at the end of each branch.
- Chitin is the substance that makes up the cell wall. There are several nuclei in the cytoplasm, which contains other cell organelles such as mitochondria, the endoplasmic reticulum, Golgi bodies, vacuoles, and oil droplets.
- It is possible for them to reproduce through vegetative, asexual, and sexual means.
- Rhizopus has a distinct life cycle.
- Rhizopus reproduces through all three phases, i.e. vegetative reproduction, asexual reproduction, and sexual reproduction.
- Vegetative reproduction is accomplished through fragmentation, and each of the fragments of a stolon develops independently, resulting in a complete mycelium.
The creation of sporangiospores and chlamydospores is the means of asexual reproduction in bacteria.
1.The Formation of Sporangiospores: Sporangiospores are created terminally in sporangia of aerial mycelium, which are also known as sporangiophores, and are a type of sporangium. They are generated in favourable environmental circumstances.
The development of sporangiophores begins on the top side of the rhizoidal node.
As nuclei and cytoplasm travel apically, the apical region of the cell swells up and forms a sporangium.Spongidium cytoplasm differentiates into two distinct regions: the denser outer region with more nuclei and the less dense central columella region with fewer nuclei and more vacuoles.
Sporangiospores are formed within the sporangium. They have several nuclei and are not mobile.After maturation, the wall of the sporangium ruptures, and the sporangiospores are expelled as a powdery mass. Each spore germinates into a new mycelium once it has been exposed to the proper conditions and substrate.
- Chlamydospores are formed as a result of the following processes: Chlamydospores are created when a favourable environment is not present. The formation of septae and the accumulation of protoplasm result in the development of an intercalary segment of mycelium. It has thick walls and detaches from the mycelium when it dries out completely. They remain dormant until the optimum growing conditions are restored, at which point they germinate and produce a new mycelium.
The merger of two suitable hyphae results in sexual reproduction. The majority of Rhizopus species (R. stolonifer) are heterothallic, which means that they have separate mycelium for mating strains that are positive and negative. R. sexualis is a homothallic bacterium.
The hyphae that are compatible with one another come together. There is a little expansion on both mycelia at the same time. It is referred to as progametangia.
In the apical area, nuclei and cytoplasm advance near one another, and progametangia establish contact.
During hyphal development, septal creation separates the apical area from rest of the hyphae. This is referred to as gametangia. As a result of their conjugation, gametangia develop a multinucleated structure.
Plasmogamy is followed by karyogamy, which results in the formation of a diploid (2n) zygote. It is referred to as a zygospore. The remaining unpaired nuclei are degenerate.
Zygospores grow in size and become thick-walled, making them more resistant to harsh environmental conditions as they mature. Zygospores germinate when they are exposed to favourable conditions.
The inner wall of the zygospore develops into promycelium, which forms the germ sporangiophore, with the germ sporangium growing apically on the germ sporangiophore.
In the course of meiosis, haploid meiospores are produced. They emerge from the germ sporangium wall upon the rupture of the wall and grow into new mycelia.
Importance in terms of the economy
- A large number of Rhizopus species are economically exploited for the production of various chemicals and alcoholic beverages.
- It is necessary to use R. oryzae in the production of cortisone and lactic acid.
- It is also used for the biosorption of heavy metals in wastewater. R. stolonifer is a plant that produces lactic acid, fumaric acid, and cortisone, among other things.
- R. delemar is a plant that is used to produce biotin as well as fumaric acid.
- Tempeh, a traditional Asian soybean fermented product, is made by fermenting soybeans with Rhizopus species.
- Rhizopus is used in the preparation of many traditional alcoholic beverages, such as Parakari (a cassava product).
Conclusion
Therefore it can be concluded, The inner wall of the zygospore develops into promycelium, which forms the germ sporangiophore, with the germ sporangium growing apically on the germ sporangiophore. In the course of meiosis, haploid meiospores are produced. They emerge from the germ sporangium wall upon the rupture of the wall and grow into new mycelia.