Fungi or mushrooms is a group of eukaryotes that mostly form multicellular filaments to form hyphal threads. Hyphae threads intertwine to form the mycelium so that it can penetrate the place to absorb nutrients. In fulfilling nutrition, fungi are classified as heterotrophs “unable to make their own food” or unable to convert inorganic compounds into organic compounds.

With a wide spread mycelium, most terrestrial ecosystems are colonized by fungi. The diversity of fungal species is currently around 100,000 species, it is estimated that there are 1.5 million species of fungi that have not been identified. (Urry et al. 2017: 652—653). The study of fungi is called mycology, in Greek mykes “fungus” and logos “science.”

Fungi play a role in most terrestrial life. Fungi can digest organic material as saprobes to recycle nutrients, so they are called saprophytes. The role of fungi that are beneficial to humans, such as being food ingredients, making antibiotics, and fertilizing plants. The role of other harmful fungi is as a parasite on humans, livestock, and cultivated plants in agriculture (Urry et al. 2017: 652—653).

Characteristics of Fungi / Mushrooms

  1. In multicellular fungi, it is composed of hyphal threads with walls cell there is chitin (polysaccharide – nitrogen found in the external skeleton of insects and other arthropods);
  2. Saprophytic, mutualism, and parasitism
  3. Most of them live on land with humid conditions
  4. Hyphal threads in multicellular fungi form the fruiting bodies
  5. Can reproduce asexually and or sexually
  6. The group of fungi is classified as unicellular or multicellular.

Body Structure of Fungi / Fungi

The body structure of the fungus / fungus is divided into multicellular and unicellular mycelium filaments for yeast or yeast groups. The body of multicellular fungi is composed of tiny filaments called hyphae (plural hyphae). Hyphae are composed of cells that line up with tubular cell walls and enclose the plasma membrane as well as the cytoplasm.

In most fungi, hyphae are divided from septa hyphae and koenositic hyphae. Septa hyphae are cells that are separated by a wall and generally have large pores, allowing the ribosome, nucleus, and mitochondria. Hyphae that have no insulation are called koenositic hyphae. The formation of koenositic hyphae is due to repeated nucleus division without cytokinesis (cytoplasmic division). Some fungi have specialized hyphae that allow them to absorb nutrients from the bodies of living things.

An example of a specialized type of hypha is the haustoria hyphae. Haustoria hyphae function to penetrate plant root cells to extract nutrients or exchange nutrients with their host. This relationship is called the “root fungal mycorrhiza.” The hyphal threads in some fungi form fruiting bodies and some differentiate to produce spores (Urry et al. 2017: 653—654). The shape of the body structure of the fungus can be seen in Figure 1.the body structure of the fungus fungi

Figure 1. Body Structure of Fungi
Image source: Urry et al. 2017: 653

Reproduction of Fungi / Fungi

Fungal reproduction is divided into asexual and sexual. Asexual reproduction generally occurs in groups of yeast and some other groups of fungi. Asexual reproduction is divided into the formation of spores asexually (by mitosis), separation of mycelium, and separation of stem cells in yeast. The group of fungi that have asexual reproduction but the sexual reproduction cycle is not known is classified into deuteromycota (in Greek, deutero “second” and mycete “fungus”) (Urry et al. 2017: 655).

Sexual reproduction starts from the union of the haploid fungal hyphae. When different hyphae meet each other, fusion occurs to form plasmogamy. The fungi compatibility test prevents hyphae from fusing with each other with hyphae from the same mycelium and increases genetic variation. The plasmogamy that is formed is the union of the cytoplasm of two different mycelium.

When plasmogamy occurs, generally the nucleus of each of the previous hyphae does not directly fuse, so that the mycelium is called heterokaryon mycelium, which consists of two or more different nuclei. The next process, namely the fusion of different nuclei to form a diploid mycelium, is called karyogamy. Kariogamy produces zygotes and develops into the meiosis stage to form haploid cells, resulting in the formation of spores as new seeds for the spread of fungi (Urry et al. 2017: 656). The process of sexual and asexual reproduction of fungi can be seen in Figure 2.the fungal reproductive cycle

Figure 2. Reproduction Cycle of Fungi
Image source: Urry et al. 2017: 656

Classification of Fungi / Fungi

The grouping of fungi is divided into four phyla, such as Zygomycota (koenositic hyphae), and fungi with septa, such as Ascomycota, Basidiomycota, and Deuteromycota.

1. Zygomycota

Zygomycota Features:

  1. The sexual reproductive structures of plasmogamy form the zygosporangium, so they are called zygomycota;
  2. The zygosporangium structure contains more than one different nucleus as a place for cariogamy and meiosis, and there is a thick and coarse layer to protect it from adverse environmental conditions for a long time;
  3. The body structure consists of hyphae that form rhizoids, stolons, and sporangiophores;
  4. Has koenositic hyphae;
  5. There are 1,000 known species of zygomycota;
  6. Reproduce asexually and sexually;
  7. Habitat on land;
  8. Has a role in food spoilage or the role of other saprophytes, as well as in the manufacture of food

Reproduction of Zyogomycota

There are two different types of mycelium that will fuse with each other, namely mycelium + and mycelium -. The adjacent mycelium forms an expansion of the hyphae or gametangium, which carries the haploid nucleus. Gametangium which is close to each other to form zygosporangium in the process of plasmogamy. When environmental conditions are favorable, cariogamy occurs to form a diploid nucleus, followed by the process of meiosis. The zygosporangium that emits turns into sporangium. The sporangium disperses the haploid spores and a new haploid mycelium is formed. The Pilobolus group can aim the sporangium towards the sunlight and scatter it in a jet of water as far as 2 m.

The spores of the sporangium grow into new mycelium and form sporangium without sexual process. Other asexual reproduction such as termination of hyphae on stolons or rhizoids to form new individuals. The reproductive cycle of zygomycota can be seen in Figure 3.zygomycota reproductive cycle

Figure 3. Zygomycota Reproductive Cycle
Image source: Urry et al. 2017: 660

Examples of Zygomycota: Rhizopus oryzae (for making tempeh), R. stolonifer, R. oligosporus, Pilobolus (Raven et al. 2017: 625-626; Urry et al. 2017: 660-661).

2. Ascomycota

Ascomycota characteristics:

  1. The sexual reproduction cycle forms the sexual spores of the ascus, in the form of a pouch, so it is called a pocket fungus;
  2. The sexual reproduction stage occurs in the fruiting body, called the ascocarpus;
  3. There are unicellular or yeast and multicellular forms;
  4. Pathogenic, decomposer, and in symbiosis with cyanobacteria to form lichen;
  5. Forming conidium as asexual reproduction in the form of specialized hyphal tips forming conidiophores as asexual spores;
  6. Habitat in sea, fresh, and land waters;
  7. There are 65,000 identified species of ascomycota

Reproduction of Ascomycota

The ascomycota mycelium has hyphae that are specialized to form the conidium. Different conidia fuse to form dikaryotic hyphae. The dicharyotic hyphae resulting from plasmogamy produces a lot of dicharyotic ascus. Karyogamy occurs within each ascus, producing a diploid nucleus. The next stage of meiosis produces a haploid nucleus. Each haploid nucleus divides by mitosis to produce eight haploid nuclei, and the cell wall around the nucleus forms ascospores. The askospora is pushed apart from the askus through the opening in the askokarp. Ascospores that have spread in the right environment, form new mycelium.

The mycelium that has germinated forms the conidiophores. The tip of the conidiophores contains conidium as haploid spores asexually. The spores of the conidiophores can develop into new hyphae to form new individuals. The reproductive cycle of ascomycota can be seen in Figure 4.the ascomycota reproductive cycle

Figure 4. Ascomycota Reproductive Cycle
Image source: Urry et al. 2017: 662

Examples of Ascomycota: Morchella esculenta (edible morel), Tuber melanosporum as truffles, Neurospora crassa for making oncom (Urry et al. 2017: 661-662).

3. Basidiomycota

Basidiomycota characteristics:

  1. Derived from Latin, “foundation;”
  2. Sexual reproduction forms basiodiocarpus;
  3. Play a role in mycorrhizae, parasites, saprophytes, and food sources;
  4. Habitat on land;
  5. There are 30,000 species that have been identified

Reproduction of Basiodiomycota

Two different haploid mycelium perform plasmogamy. The result of plasmogamy is dicharyotic mycelium. Environmental factors, such as temperature and rainfall trigger the mycelium to form basidiocarpus. The basidiocarpal hyphae are lined with terminal dikaryotic cells, called the basidium. Kariogamy in the basidium produces a diploid nucleus, which proceeds to the meiosis stage. The result of meiosis is four haploid nuclei, each developing into a basidiospora. Ripe basiodiospores are expelled and spread by the wind. Basiodiospores attached to a suitable environment develop into new haploid mycelium.

Asexual reproduction of basidiomycota can occur with termination of hyphae. The severed hyphae can form new basidiomycota. The reproductive cycle of basidiomycota can be seen in Figure 5.the basidiomycota reproductive cycle

Figure 5. The Basidiomycota Reproductive Cycle
Image source: Urry et al. 2017: 664

Examples of Basidiomycota: Dictyphora, Amanita phalloides are poisonous, Puccinia as a rust fungus (Urry et al. 2017: 663-664).

4. Deuteromycota

Deuteromycota Features:

  1. Groups that reproduce asexually, with unknown sexual cycles (Fungi imperfecti / imperfect fungi);
  2. Pathogenic and saprophytic;
  3. Has septa hyphae and is microscopic in size;
  4. Multicellular organisms

Asexual Reproduction of Deuteromycota: by termination of hyphae that can develop into new mycelium.

Examples of Deuteromycota: Fusarium, Penicillium camemberti, P. roqueforti, Amorphoteca.

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