Kingdom Fungi

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Kingdom Fungi
Dr. ROD ALFONSO Head, Development and Quality
Assurance Unit
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Requirements to get Good Grade

1. Perfect Attendance
2. Participate actively in classroom activities
3. Pass assignment on time
4. Pass all quizzes and major exams
5. Good attitude

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Learning Objectives

• At the end of the lesson, students will be able
  to
• Define mycology Define a fungus
• Describe the characteristics of fungi
• Describe the distribution of fungi in nature
• Explain why there are few invasive fungal
  infection.
• Describe the characteristics of yeasts and how
  they reproduce
• Discuss the significance of yeast in food
  industry, in medicine and biofuel industry.
• Describe molds
• Differentiate hypha, thallus and mycelium
• Differentiate between septate and coenocytic
  hyphae
• Explain dimorphic fungi
• Discuss the beneficial and harmful effects of
  fungi

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Mycology

• Mycology is the study of fungi ( yeasts, molds
  and mushrooms)

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001
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What is a fungus?

• A eukaryotic, heterotrophic organism devoid of
  chlorophyll that obtains its nutrients by
  absorption, and reproduces by spores.
• The primary carbohydrate storage product of fungi
  is glycogen.
• Most fungi have a thallus composed of hyphae
  (sing. hypha) that elongate by tip growth

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The Characteristics of Fungi

• Eukaryotic(true nucleus)
• Larger, more complex than bacteria
• Lack chlorophyll
• Chitin, glucan mannan are the complex
  carbohydrates found in their cell wall
• Reproduce sexually and asexually
• Cell wall contains ergosterol
• Heterotrophic (require organic carbon)

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Fungal Fast Facts

• Fungi are all around us
• We touch them, we swallow them, we breathe them
• There are more than 1.5 million fungal species in
  nature

• Yet only about 100 cause human disease
• Most cause superficial infections, some cause
  allergic reactions
• Few cause invasive infections

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Why so few Invasive Infections?
Host/Pathogen BalanceNormal Circumstances
Fungal Factors
Anatomical barriers
Virulence
Host Factors
Adaptive immunity
Fungal Burden
Innate defenses
Infection
Protection
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Yeast - Major Characteristics

• Unicellular Fungi, nonfilamentous, oval or
  spherical cells
• Eukaryotic
• Facultative anaerobes
• When oxygen is available, they carry out aerobic
  respiration.
• When oxygen is not available, they ferment
  carbohydrates to produce ethanol and carbon
  dioxide.
• Capable of forming colonies on solid culture
  media (see pictures on the right).

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Yeast - Reproduction

• They reproduce either asexually (most common) or
  sexually.
• Asexual reproduction is through budding or binary
  fission.
• Sexual reproduction (if any) results in the
  formation of the appropriate spore structure.

Saccharomyces cerevisiae
Schizosaccharomyces octosporus
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Yeast Significance

• Food Industry
• Fermentation of bread, beer, and wine. E.g.
  Saccharomyces cerevisiae (also called bakers
  yeast or sugar yeast) used in baking and
  fermenting of alcoholic beverages.

• Medical
• E.g. Candida albicans - common in the human
  mouth, but can become pathogenic and cause
  Candidiasis (oral and/or genital infection).

• Biofuel Industry
• Production of ethanol for car fuel.

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• 2. Molds and Fleshy Fungi
• Multicellular, filamentous fungi.
• Identified by physical appearance, colony
  characteristics, and reproductive spores.
• Thallus Body of a mold or fleshy fungus.
  Consists of many hyphae.
• Hyphae (Sing Hypha) Long filaments of cells
  joined together.
• Septate hyphae Cells are divided by cross-walls
  (septa).
• Coenocytic (Aseptate) hyphae Long, continuous
  cells that are not divided by septa.
• Hyphae grow by elongating at the tips.
• Each part of a hypha is capable of growth.
• Vegetative Hypha Portion that obtains
  nutrients.
• Reproductive or Aerial Hypha Portion connected
  with reproduction.
• Mycelium Large, visible, filamentous mass made
  up of many hyphae.

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Characteristics of Fungal HyphaeSeptate versus
Coenocytic
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Hyphae

• Tubular
• Hard wall of chitin
• Crosswalls may form compartments ( cells)
• Multinucleate
• Grow at tips

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Hyphal growth

• Hyphae grow from their tips
• Mycelium extensive, feeding web of hyphae
• Mycelia are the ecologically active bodies of
  fungi

This wall is rigid
Only the tip wall is plastic and stretches
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Mycelium Large, Visible Mass of Hyphae
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• Dimorphic Fungi
• Can exist as both multicellular fungi (molds) and
  yeasts.
• Many pathogenic species.
• Mold form produces aerial and vegetative hyphae.
• Yeast form reproduces by budding.
• Dimorphism in pathogenic fungi typically depends
  on temperature
• At 37oC Yeast form.
• At 25oC Mold form.
• Dimorphism in nonpathogenic fungi may depend on
  other factors Carbon dioxide concentration.

Yeast at 370C
Mold at 250C
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HUMAN-FUNGUS INTERACTIONS

• Beneficial Effects of Fungi
• Decomposition - nutrient and carbon recycling.
• Biosynthetic factories. Can be used to produce
  drugs, antibiotics, alcohol, acids, food (e.g.,
  fermented products, mushrooms).
• Model organisms for biochemical and genetic
  studies.
• Harmful Effects of Fungi
• Destruction of food, lumber, paper, and cloth.
• Animal and human diseases, including allergies.
• Toxins produced by poisonous mushrooms and within
  food (e.g., grain, cheese, etc.).
• Plant diseases.