Mucor NOtes

Mucor
Kingdom - Mycota
class – Zygomycetes
order - Mucorales
Family - Mucoraceae
Genus – Mucor
Common name - Black mold or Pin mold

Habitat
 Mucor is a saprophytic fungus growing generally on dead and decaying organic matters like dung, pickles, bread, rotten fruits, leather and humus-rich soil. 

Structure

§ The vegetative body Mucor is composed of a mass of white, delicate cottony thread-like structure called mycelium.

§ Mycelium is long, slender, branched, aseptate, and multinucleated structure. Such a type of mycelium is called coenocytic mycelium. 

 

Mycelium consists of Submerged (subterranean) or Rhizoidial hyphae, Prostrate hyphae, and Aerial hyphae.

1.    Submerged (Subterranean) hyphae They are more branched hyphae that penetrate the substratum. They help in the fixation and absorption of soluble food.

2.    Prostrate hyphae They are more branched hyphae that spread in all directions on the surface of the substratum.

3.    Aerial hyphae or Sporangiophores They are vertically growing erect hyphae from the prostrate hyphae and bear sporangia at their tip. They help in asexual reproduction.

§ The wall of hypha is made up of chitin and surrounded the cytoplasm.

§ Cytoplasm consists of the Golgi body, Mitochondria, Endoplasmic reticulum, Ribosomes, Vacuoles, and true Nucleus.

§ Food reserve occurs in the form of glycogen and oil. The hypha is multinucleate.

Reproduction -
Reproduction of Mucor takes place by the vegetative, asexual, and sexual methods.

1.    Vegetative reproduction:The vegetative plant body (hyphae) break into one or more fragments by accidentally or decaying. Each of the fragments germinates into new individuals under favorable conditions.

2.     Asexual reproduction: Asexual reproduction takes place by

§  Sporangiospores
§  Chlamydospores and
§  Oidia

 

a.    Sporangiospores or spores

§  They are minute, brownish-black, multinucleate spores, produced in sporangium. At maturity, the prostrate hyphae give erect aerial hyphae. These are called sporangiophores. At the tip of each, sporangiophore, protoplasm is collected and it swells up into a spherical sac called sporangium. The peripheral protoplasm of sporangium is denser and the central protoplasm is vacuolated.

§  The central vacuolated protoplasm produces a dome-shaped structure called the columella. The columella functions for nutrient exchange between the active protoplasm below and the developing spores inside the upper portion of the sporangial head.

§  The outer region with dense protoplasm undergoes cleavage and forms multinucleate segments. Each segment rounds off and secretes a dark wall around it. Now it is called sporangiospores.
      

     §   After maturity, the sporangial wall breaks, and the spores are liberated out. Under the suitable conditions, the spore germinates and form hypha and then mycelium.

 

b.      Chlamydospore: (Thick-walled asexual resting spore) During unfavorable conditions, the mature mycelium becomes septate and the protoplasm of hyphae accumulates to form around and thick-walled structure known as chlamydospore. During the favorable condition, each chlamydospore germinates and forms hypha and then mycelium.

c.       Oidia: In a liquid medium, rich in sugar, the hyphae become septate. The cells round off and separate to form oidia. These oidia increases in number by budding in a Yeast-like fashion. This is called the torula condition.

Sexual reproduction of Mucor

§  Mucor shows sexual reproduction by isogamy that takes place by gametangial copulation (Conjugation) during unfavorable conditions.

§  Mucor is heterothallic and consists of mycelia with two mating types + strain (male) and – strain (female).

§  At the time of sexual reproduction, two hyphae of different strains come in contact and become attached by small outgrowths. These outgrowth swell up at the point of attachment by accumulating cytoplasm and nuclei to form a short lateral club-shaped structure, the progametangia.

§  Each progametangia forms basal suspenser and terminal gametangia by means of a transverse wall. The gametangia have densely granular, multinucleate protoplast, whereas the suspensor has a highly vacuolated protoplast with fewer nuclei.

§  At maturity, the wall between two gametangia dissolves and their protoplast fuse together to form a diploid Zygospore.

§  The zygospore is a large dark, thin-walled warty (not smooth, rough) structure.

 Germination of Zygospore

·       During favorable conditions the wall of zygospore rapture and endosporium comes out in the form of a vertical germ tube called promycelium. The tip of promycelium swells up and form rounded germ sporangium which produce non-motile uninucleated haploid germ spores.

·       These germs are released out after breakage the germ sporangium. These germ spores are carried out by wind and reach a suitable habitat. Each germ spore germinates and first forms hyphae and then mycelium.

 

Life cycle of Mucor

 

Economic importance of Mucor

Ø  Mucor takes part in decaying organic matter in the soil and helps to make the soil fertile.

Ø  Some species of Mucor like Mucor javanicus are utilized in the fermentation of alcohol.

Ø  Mucor mucedo is responsible for spoilage of jam, frozen meat, pickles, and other foodstuffs.

Ø  Few Species like Mucor pusillus attacks human internal organs like alimenting canal and lungs and cause mycosis.

Ø  Many species of Mucor and causing the rotting of fruits and vegetables.