MYCOLOGY (MIC 206) FUNGAL REPRODUCTIONMDM ASLIZAH MOHD ARIS
Reproduction Filamentous fungi Asexually by fragmentation of hyphae Asexual and sexual reproduction by spores Yeasts Asexually by budding or fission: Fission: e.g. Schizosacchromyces pombe. Budding e.g. Saccharomyces cerevisiae. Sexual reproduction by spores (in high stress condition)
Terms Fragmentation can occur whereby mycelium are torn apart by external forces and these bits can start new individuals if conditions are favourable. Fission is a simple splitting of a cell into two new daughter cells by constriction and the formation of a cell wall e.g. yeast. Budding is the production of small outgrowths (bud) from a parent cell and as the bus is formed, the nucleus of the parent cell divides and one daughter nucleus migrates into the bud. The bud increase in size while still attached to the parent cell and eventually breaks off and forms a new individual. Yeast reproduce via budding but do some other fungi in different conditions.
Kingdom Fungi – 4 Major Phyla1. Phylum Zygomycota = the Bread Molds Rhizopus – black bread mold2. Phylum Ascomycota = the Sac Fungi Yeast, morels, truffles3. Phylum Basidiomycota = the Club Fungi Mushrooms, puffballs, bracket fungi, rusts, smuts, toadstools4. Phylum Deuteromycota = the Fungi Imperfecti
Reproduction Teleomorphs-produce both sexual and asexual spores Anamorphs- lost ability to reproduce sexually- Penicillium belonged to Deuteromycota now classified as anamorphs of other phyla: rRNA & Woese most are Ascomycetes
Asexual Spores More important type of reproduction as it occurs several times throughout the season. Produced by fragmentation of aerial hyphae Progeny genetically identical to parent
Production of spores is most common type ofreproduction.Production of spores where each sporegerminate to form a germ tube that grows intothe mycelium.Spores can be of various colours, depending on: the colour of hyaline (green, yellow, orange, red, brown, black); shape (oval, oblong, needle-shaped, helical); number of cells (one to many); arrangement of cells and where they are situated.
Several types of spores:ConidiosporesBlastosporesChlamydosporesSporangiosporesArthrospores
ASEXUAL SPORESConidiospore Multiple (chains) or single spores formed at the end of an aerial hypha Not enclosed within a sac Eg: Aspergillus spp. and Penicillium spp.
Conidial fungusreproduces by means of asexualspores called conidiaConidia vary greatly in shape, sizeand colorMost of the common householdmolds & mildews are conidial fungi
ASEXUAL SPORES (cont.) Blastospores A bud coming off the parent cell Candida albicansBlastospore
ASEXUAL SPORES (cont.)Chlamydospore Formed within hypha Thick-walled spore • Candida albicans
ChlamydosporesThe chlamydospore is a method of producing asubstantial resting spore very quicklyNutrient is shunted from adjacent cells into apreferred cell and it swells up, converts nutrientmaterials to oil droplets for efficient storage, thenrounds off with a thick, often roughened outer wallfor protection
ASEXUAL SPORES (cont.) Sporangiospores Hundreds formed within a sac (sporangium) at the end of an aerial hypha Rhizopus spp.
Sexual Reproduction• Union of two nuclei.• The entire thallus can be converted into one or more reproductive structures.• Somatic and reproductive phases do not occur together in the same individual and this is called holocarpic.• In majority of fungi, only a portion of the thallus give rise to reproductive organs and they are called eucarpic.
Sexual Reproduction (con’t) Some fungal species produce distinguishable male and female sex organs on each thallus – hermaphroditic or monoecius. These species can reproduce sexually by itself. Other species consist of male or female thalli – dioecious and therefore cannot reproduce itself.
The sex organs are called gametangia /gametangium which may differentiate intogametes.The male gametangium are calledantheridia / antheridium and the female arecalled oogonia / oogonium.Heterokaryosis – the existence of differentkinds of nuclei in the same individual.
Sexual Spores Three phases of development Plasmogamy: a union of two protoplasts bringing about the nuclei close together and within same cell. - haploid nucleus of a donor cell (+) penetrates the cytoplasm of a recipient cell (-) Karyogamy: Fusion of the two nuclei. Formation of a dikaryon – a binucleate cell containing two nuclei from each parent - the 2 nuclei fuse to form a diploid nucleus Meiosis: diploid nucleus gives rise to haploid nuclei - Sexual spores, some + , some -,some recombinants - Sexual spores used to classify fungi into divisions
Classification of these groups First three groups is based on their method of sexual reproduction 4th group, the Deuteromycetes, have NO sexual reproduction
Zygomycota (Conjugation Fungi) Also known as bread molds. Saprophytic molds with coenocytic hyphae (lack septa). Asexual Reproduction: Used most of the time. Sporangiospore: Asexual spore enclosed within a sporangium or sac at the end on an aerial hypha. Sexual Reproduction: Occurs through conjugation, the joining of hypha of two different strains (plus and minus). Zygospores: Sexual spores which are enclosed in a thick, resistant wall. Generally not pathogens. Rhizopus stolonifer: Common black bread mold. May cause opportunistic infections in diabetes patients
Zygomycota – common moldsThe fungalmass ofhyphae,known as theMYCELIUMpenetrates thebread andproduces thefruiting Mycelia = a mass of hyphae orbodies on top filamentsof the stalks.
Rhizoids = root-like hyphaeThe zhizoids meet underground and mating occurs between hyphae of different molds (SEXUAL REPRODUCTION)
Ascomycota (Sac Fungi) Molds with septate hyphae and some yeasts. Asexual Reproduction: Conidiospores not enclosed in a sac. Become airborne easily. Form chains (broom-like structures). Sexual Reproduction: Ascospores enclosed in a sac-like structure (ascus). Include common antibiotic producing fungi and yeasts, and several human pathogens. Penicillium notatum (Produces penicillin) Saccharomyces (Brewer’s yeast) Trychophyton (Athlete’s foot) Aspergillus (Carcinogenic aflatoxin in peanuts),
Life Cycle of Eupenicillium (Ascomycete)Reproduces Asexually and Sexually
Basidiomycota (Club Fungi) Have septate hyphae. Include mushrooms, toadstools, rusts, and smuts. Sexual Reproduction: Produce basidiospores: Spores formed externally on a club shaped sexual structure or base called basidium. Asexual Reproduction: Through hyphae. Examples: Amanita: Mushroom produces lethal toxins to humans. Claviceps purpurea: Produces ergot toxin in wheat and rye.
Bracket Fungi Puff BallsBasidiomycete Fungi that all produce Basidiospores Jelly Fungi Mushrooms
Other Basidiomycetes Rusts and SmutsRust infecting Rust infecting a Whitrot Smutwheat leaves Leaf digesting old wood
Deuteromycota (Imperfect Fungi)Regarded as imperfect because they exhibit no sexualstage has been observed in their life cycle
Deuteromycota – the FungiImperfectiResembleAscomycetes, but theirreproductive cycle hasnever been observed Penicillium fungiDifferent fromAscomycetes becausethere is a definite lackof sexual reproduction,which is why they are Up Closecalled Imperfect Fungi
Parasexual Reproduction This phenomenon occurs whereby the three steps in sexual reproduction take place not at specific points in the life cycle. Several Ascomycota species are not known to have a sexual cycle. Such asexual species may be able to undergo genetic recombination between individuals by processes involving heterokaryosis and parasexual events. Parasexuality refers to the process of heterokaryosis, caused by merging of two hyphae belonging to different individuals, by a process called anastomosis, followed by a series of events resulting in genetically different cell nuclei in the mycelium.
QUESTIONS1. Differentiate between the types of spores.2. Differentiate between the different types of asexual reproduction.3. Name one (1) fungus that has a parasexual type of reproduction.