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Mucor & Rhizopus MUCOR & RHIZOPUS (Pin mold) (Common bread mold) or Black mold of bread SYSTEMATIC POSITION :: Division : Eumycophyta Class : Phycomycetes Sub. Class : zygomycetes Order : mucorales Family : mucoraceae Genus : Mucor/Rhizopus https://madanacademy.com/ Rhizopus and Mucor are saprophytic fungi and in laboratory can be obtained on moist bread. Rhizopus and Mucor are also called as bread mold. STRUCTURE OF MYCELIUM :: It is branched, coenocytic, aseptate and vacuolated. The hyphal wall is made up of chitin. Some amount of glucosamine, galactose, protein, lipid, Mg and Ca are also present in the cell wall. In cytoplasm, storage food is present in the form of oil droplets and glycogen bodies. REPRODUCTION :: (i) Vegetative reproduction (ii) Asexual reproduction (iii) Sexual reproduction Vegetative Reproduction :: It takes place by fragmentation. Asexual Reproduction :: By aplanospore formation - • Sporangia are aseptate and aerial. • Sporangium develops on sporangiophores. • Sporangiophores are branched (Mucor mucedo) or unbranched (M.jenevensis). • Sporangiophores come out from mycelium and their distal ends swell up. • The swollen apices accumulate cytoplasm, nuclei and food. Now it is called sporangium (plural- sporangia). • In this stage protoplast of sporangium is differentiated into a peripheral dense multinucleated region and central region with small flattened vacuole. • Nucleus are arranged in peripheral region. The peripheral region of sporangium is fertile. • Central vacuolated region is sterile. It is hemispherical or club shaped which is called columella. • At the stage of spore formation protoplast of peripheral region of sporangium get divided into many multinucleated segments (2-10 nuclei in each segment). • Each segment secretes a wall around itself and form aplanospores. • When they mature outer wall of sporangium ruptures to release the spores in air. • These spores germinate in favourable conditions and form new mycelium. • https://madanacademy.com/ By Chlamydospores - • Asexual reproduction also takes place by chlamydospores. • When unfavourable condition comes, mycelium becomes septate. • Protoplast of each cell aggregates, to become spherical and secretes a thick wall around itself. • These are perennating structure which can survive in unfavourable conditions. Oidia - • When mycelium gorws in a liquid medium then it becomes septate and thin-walled. These cells are called oidia. • Oidia are similar to buds of yeast. • Fermentation takes place by oidia in sugar solution and alcohol is formed. • Oidia are formed in a chain. This stage is called torula stage. SEXUAL REPRODUCTION :: → Isogamous type It takes place during the absence of nutrient susbstances. In this process gametangial copulation takes place between two gametangia. Both homothallic and heterothallic species are occur in these fungi. But most of the species are heterothallic. Mucor mucedo (Dung mold) – heterothallic R.stolonifer – heterothallic Rhizopus nigricans – heterothallic R. sexualis – homothallic (species found as obligate parasite in higher plant) M.hiemalis – homothallic https://madanacademy.com/ When two fungal hyphae which are respectively (+) and (–) strains come close to each other, then these fungal hyphae produce some outgrowths. These outgrowths are called "progametangia". Anterior parts of progametangia are filled with cytoplasm and nuclei. Now these progametangia (which are different in strains), come in contact and a septum is formed just behind the contact place. Now the terminal part is called gametangium & long basal part is called suspensor, which is vacuolated. The multinucleate undifferentiated protoplast of each gametangium is termed as coenogamete or aplanogamete. In mature gametangium at the place of contact, walls of gametangia are dissolved and fuse together and then zygospore is formed. In zygospore diploid nuclei are formed while haploid nuclei are degenerate. A black coloured, thick and ornamented coat is formed around the zygospore [Dormant stage approximately 6 months (In Rhizopus)]. Which germinate in favourable condition. GERMINATION OF ZYGOSPORE :: During germination outer wall of zygospore get ruptured. A germ tube protrudes out from this ruptured place, it is called promycelium/Promycelial Hypha. At the apex of promycelium, a sporangium is formed which is called germsporangium or zygosporangium. In Rhizopus, at the time of germination Meiotic division takes place in zygospore (delayed) whereas in Mucor, meiotic division takes place in zygospore soon after karyogamy. Each nucleus is converted into spore. These spores germinate to form fungal hypha. HETEROTHALLISM :: "Blakeslee" discovered heterothallism first in Mucor mucedo. According to Blakeslee two types of species are found in order mucorales which are called respectively homothallic and heterothallic species. Homothallic e.g. M.hiemalis. Hetrothallus species – e.g., M.mucedo and R.Stolonifer. DISEASES :: Rhizopus stolonifer – causes soft rot disease of vegetable crops./ Soft rot disease of sweat potato. M.pusilus – infects genitalia of human beings Rhizopus arrhizus – Causes fruit rot of apple. R.artocarpi – fruit drop of Jack fruits. DIFFERENCE BETWEEN RHIZOPUS & MUCOR :: Rhizopus Mucor 1. Mycelium is differentiated into three Mycelium is undifferentiated, i.e. it has kind of hyphae-stolons, rhizoids and only one kind of hyphae. sporangiophores. 2. Rhizoids present. Rhizoids absent. 3. Food material is absorbed mainly by Food is absorbed by the entire mycelial rhizoids. surface. 4. Sporangiophores occur in tufts from the Sporangiophores usually occur singly from stolons opposite the rhizoids. any point on the mycelium. 5. Spores easily disseminated by wind. Spores remain adhered to columella and thus spores are not easily disseminated. https://madanacademy.com/ Mucor Exercise Q.1 Reproduction in Mucor takes place by Q.9 Coenogametes are formed in - (1) Anisogametes (2) Isogametangia (1) Mucor (2) Puccinia (3) Agametes (4) None (3) Pencillium (4) Ustilago Q.2 The zygospore of Mucor thick walled and Q.10 Torula condition occurs in its colour is (1) Mucor (2) Rhizopus (1) Blue (2) White (3) Both (1) and (2) (4) Puccinia (3) Green (4) Black Q.11 Mucor mucedo is a - (1) Homothallic fungus Q.3 Zygospore of Mucor germinates to form (2) Heterothallic fungus (1) Mycelium (2) Promycelium (3) Heteroecious fungus (3) Germ tube (4) Hyphae (4) None Q.4 In Mucor, heterothallism was discovered Q.12 Mucor belongs to order - by - (1) Mucoraceae (2) Mucorales (1) Lederberg and Tatum (3) Zygomycetes (4) Oomycetes (2) Debary (3) Pontecorvo Q.13 Dung-mold is - (4) Blakeslee (1) Rhizopus stolonifer (2) Mucor mucedo Q.5 Yeast like budding of oidia in Mucor is (3) Aspergillus flavus termed as (4) Clostridium tetani (1) Gongrosira stage (2) Torula stage (3) Palmella stage (4) None Q.14 Which one of the following life cycles is associated with mucor Q.6 Thick walled spore like structure formed in (1) Heteromorphic (2) Haplontic the mycelium of Mucor are named as - (3) Diplontic (4) Isomorphic (1) Hypnospore (2) Akinetes (3) Oidia (4) Chlamydospores Q.15 Mucor is - (1) Heterothallic and heterotrophic Q.7 How many zones are present in the (2) Heterotrophic and heteroecious sporangia of Mucor which develops from a vegetative mycelium - (3) Heteroecious and heterosporous (1) Two (2) Three (4) heterosporous and heterothallic (3) Four (4) Five Q.16 Bread mold is the common name of - Q.8 Zygospores are formed in - (1) Batrachospermum (2) Rhizopus (1) Puccinia (2) Penicillium (3) Agaricus (4) Bacillus (3) Alternaria (4) Mucor Q.17 In Mucor species, usually isogamy takes place between - Q.22 Mucor shows [MP PMT 2002] (1) Same strains (2) (+) and (–) strain (1) Isogamy (3) Zygospores (4) Microspores (2) Anisogamy (3) Oogamy Q.18 In mucor, stored food is – (4) None of the above (1) Glycogen and oil (2) Starch (3) Leucosine and oil (4) Foridean starch Q.23 Which of the following environmental conditions are essential for optimum growth Q.19 Mucor is - of Mucor on a piece of bread ?[CBSE 2006] (1) With chlorophyll A. Temperature of a about 25ºC (2) Without chlorophyll B. Temperature of a bout 5ºC (3) With carotenes C. Relative humidity of about 5% (4) None D. Relative humidity of about 95% E. A shady place Q.20 Mycelium of mucor is [MP PMT 2000] F. A brightly illuminated place (1) Septate and unicellular (1) B, D and E only (2) B, C and F only (2) Septate and multicelluar (3) A, C and E only (4) A, D and E only (3) Asptate and Uninucleate (4) Coenocytic Q.21 Sporangiospores of mucor is - [MP PMT 2002] (1) Haploid (2) Diploid (3) Triploid (4) Polyploid https://madanacademy.com/ https://madanacademy.com/ Answer Key MUCOR & RHIZOPUS EXERCISE Ques. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Ans. 2 4 2 4 2 4 1 4 1 3 2 2 2 2 1 Ques. 16 17 18 19 20 21 22 23 Ans. 2 2 1 2 4 1 1 4 .
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