Fungi L. Dalia Kamal Eldien MSc in Microbiology Lecture NO: 8

Outlines At the end of this lecture, the student should know:- Definition of mycology Benefit of fungi Harmful effects of fungi General properties of fungi Morphology of fungi

Introduction The mycology is a discipline of biology which deals with the study of fungi. The medical mycology is a branches that deal with the study of pathogenic fungi to man and animal, the fungal infections now a day are in increasing rate Fungi can cause mild infections or trigger allergic reactions or produce serious life-threatening disease.

Beneficial effects of fungi 1-Decomposition : Lower fungi produce enzyme break down the organic dead materials 2-Biosynthetic factories: The fermentation property is used for the industrial production of alcohols, fats, citric& gluconic acids 3-Important sources of antibiotics: Such as Penicillin (produced by Penicillium chrysogenum), Cephalosporin produced by (Cephalosporium acremonium)

Beneficial effects of fungi 5-Model organisms for biochemical and genetic studies e.g.: Neurospora crassa, Saccharomyces cerviciae is extensively used in recombinant DNA technology 6-Some fungi are eatable e.g. Mushrooms 7-Some fungi are used in food production: e.g. Yeasts used in bakery, yogurt, cake……..

Mushrooms

Cake& cheese (yeast)

Harmful effects of fungi Destruction of food, lumber (wood), paper, and cloth. Food poisoning, toxins produced by poisonous mushrooms (Mycetism and Mycotoxicosis). Plant diseases. Damage of agricultural products (vegetables& cereals in the godown) Damage the products such as magnetic disks, glass lenses, marble statues, bones and wax. Animal and human diseases.

Destruction of food by fungi

General properties of fungi They are eukaryotic cells contain membrane bound cell organelles including nuclei, nucleic acid (DNA&RNA) mitochondria, Golgi apparatus, endoplasmic reticulum, lysosomes etc……. Possesses 80S ribosome's. Have Ergosterols in their membranes Have a rigid cell wall made of chitin Non-motile (this feature that separates them from animals)

Eukaryotic cell

General properties of fungi Are heterotrophs, but fungi lack chlorophyll Food storage is generally in the form of lipids and glycogen. All fungi require water and oxygen and there is no obligate anaerobes. Typically reproduce asexually and/or sexually .

Reproduction in fungi Fungi can reproduce asexually or/ and sexually Asexual reproduction is the commonest mode in most fungi Asexual spores are produced following mitosis, where as sexual spores are produced following meiosis. A fungus that reproduces sexually is known as a teleomorph. A fungus that reproduces asexually is known as a anamorph

Morphology of fungi Dimorphic fungi Polymorphic fungi Fungi exist in two fundamental forms; The filamentous or molds form The yeast form Dimorphic fungi Polymorphic fungi

Filamentous fungi The main structure element are cylindrical tube like structures refer to as hypha(e) The hyphae may be branched or non branched They may be septate or aseptate (coenocytic), hyphae usually have cross walls that divide them into numerous cells called septa& have small pores through which cytoplasm is continuous throughout the hyphae.

Filamentous fungi Amass of hyphae is known as mycelium Most molds have a fuzzy or woolly appearance because of the formation of mycelia

Septated& non septated hypha

Identify?

Yeast Yeasts are unicellular cells with different shape and size round, oval or elongated Some yeast are produce polysaccharide capsule They reproduce by budding or binary fission. During fission, two cells of equal size are formed. These cells continue to grow from the tips of the cell and divide only after a medial fission is formed.

Budding in yeast This process involves lysis of the yeast cell wall so that a bud (blastospore)can form. As this structure enlarges, the nucleus of the parent cell undergoes mitosis. Once the new nucleus is passed into the daughter cell, a septum forms and the daughter cell breaks free.

Budding in yeast In some cases the buds fail to detach from mother cell, and elongate thus forming a chain of elongated hyphae like filament called pseudohyphae, This property is seen in Candia albicans.

Budding in yeast

Dimorphic fungi The term dimorphism refers to the ability of some fungi to exist in two forms, dependent on growth conditions. Dimorphic fungi have the ability to shift from the yeast form to the filamentous (mold) form, and vice versa.  They can exist in filamentous or yeast form depending on the condition of growth, mainly the temperature

Dimorphic fungi The yeast or tissue state is seen in vivo or when the organism is grown at 37° C with increased CO2. The mold phase is seen when the organism is grown at room temperature (22° to 25° C) in ambient air conditions Example: Histoplasma Capsulatum

Polymorphic fungi Polymorphic fungi have both yeast and filamentous forms in the same culture. This characteristic occurs despite growth conditions and is best observed in Exophiala species, in which the yeast phase is typically observed initially, followed by the filamentous phase as the colony ages.

Introduction Fungi Kingdom show a great diversity in morphology and habitat. This Kingdom is enormous, the identified species and those not yet classified add up to over 300,000 species. The majority of these species are microscopic fungi A relatively small number of species have reproductive systems known as “mushrooms” that can be easily observed.

Reproduction in fungi Fungi reproduce asexually and/or sexually Asexual reproduction is the commonest mode in most fungi Asexual spores are produced following mitosis where as sexual spores are produced following meiosis.

Classification of fungi There are many ways for fungi classification, but the most practical approaches based on: Method of reproduction (Sexual or asexual) Type of hyphae (septated or non septated)

Classification of fungi Basing on those criteria they classify the fungi in to four phyla Zygomycota, (now a day known as Glomeromycota) Ascomycota Basidiomycota Deuteromycota (in past known as fungi imperfecti)

Scientific classification Kingdom: Fungi Phylum: Zygomycota (Glomeromycota) Order: Zygomycetes

Zygomycetes Hyphae are aseptate Reproduce sexual and asexual Commonly known as bread molds

Scientific classification Kingdom: Fungi Phylum: Ascomycota Class : Ascomycetes

Ascomycetes The hyphae of ascomycetes are septate Reproduce sexual and asexual

Scientific classification Kingdom: Fungi Phylum: Basidiomycota Class: Basidomycetes

Basidomycetes Have septated hyphae Reproduce sexually only Less medically important group Example: Mushrooms

Deuteromycetes Have septated hyphae Reproduce sexually and asexually, but mostly asexually Are the most medically important group

Home work Compare between bacteria, virus& fungi

Sources Lippincott's Illustrated Reviews: Microbiology, 3rd Edition (2012)- Richard A. Harvey- Bruce D. Fisher- Richard A. Harvey- (chapter 20) Textbook of Diagnostic Microbiology-Fifth edition- Connie R. Mahon, MS- Donald C. Lehman, EdD, MT(ASCP), SM(NRM) - George Manuselis, MA, MT(ASCP)- Elsevier (2015) (Part II –page 589)