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Questions and Answers
What is the role of the macro nucleus in protozoa?
What is the role of the macro nucleus in protozoa?
How do most protozoa primarily reproduce?
How do most protozoa primarily reproduce?
Which of the following is not a method of reproduction observed in protozoa?
Which of the following is not a method of reproduction observed in protozoa?
What defines the two distinct nuclei found in some ciliates?
What defines the two distinct nuclei found in some ciliates?
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What two basic methods are involved in controlling microbial growth?
What two basic methods are involved in controlling microbial growth?
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What is the phenomenon where dimorphic fungi switch from the yeast form to the mold form called?
What is the phenomenon where dimorphic fungi switch from the yeast form to the mold form called?
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Which of the following describes the primary source of nutrients for most fungi?
Which of the following describes the primary source of nutrients for most fungi?
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What type of respiration is primarily used by fungi?
What type of respiration is primarily used by fungi?
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Which of these statements about fungi is true?
Which of these statements about fungi is true?
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Endophytic fungi serve what primary purpose in plants?
Endophytic fungi serve what primary purpose in plants?
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Which statement best describes obligate symbiosis in fungi?
Which statement best describes obligate symbiosis in fungi?
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What is the main storage polysaccharide found in fungi?
What is the main storage polysaccharide found in fungi?
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Lichens are a combination of which two life forms?
Lichens are a combination of which two life forms?
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What is the primary method used for the long-term viability of microorganisms?
What is the primary method used for the long-term viability of microorganisms?
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Which of the following represents a metabolically inactive preservation technique?
Which of the following represents a metabolically inactive preservation technique?
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What is the temperature associated with freezing and low temperature storage for effective preservation?
What is the temperature associated with freezing and low temperature storage for effective preservation?
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What fungal species is associated with causing Aflatoxin B1?
What fungal species is associated with causing Aflatoxin B1?
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Which of these methods is NOT considered a metabolically active preservation technique?
Which of these methods is NOT considered a metabolically active preservation technique?
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Which fungal toxin is a significant risk factor for hepatocellular carcinoma?
Which fungal toxin is a significant risk factor for hepatocellular carcinoma?
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What is the duration of viability associated with cryopreservation methods?
What is the duration of viability associated with cryopreservation methods?
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Which of the following is NOT a use of fungi in pharmaceuticals?
Which of the following is NOT a use of fungi in pharmaceuticals?
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What is the role of normal flora in relation to pathogenic bacteria?
What is the role of normal flora in relation to pathogenic bacteria?
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Which of the following bacteria is known as a professional pathogen resistant to methicillin?
Which of the following bacteria is known as a professional pathogen resistant to methicillin?
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Which characteristic differentiates fungal cell walls from bacterial cell walls?
Which characteristic differentiates fungal cell walls from bacterial cell walls?
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Why are fungal infections often more difficult to treat than bacterial infections?
Why are fungal infections often more difficult to treat than bacterial infections?
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What is a common cause of candidiasis?
What is a common cause of candidiasis?
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How do MRSA and VRSA acquire resistance genes?
How do MRSA and VRSA acquire resistance genes?
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Which of the following is a superficial fungal infection?
Which of the following is a superficial fungal infection?
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What is one of the major challenges in treating fungal infections?
What is one of the major challenges in treating fungal infections?
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What is the role of fungi in the preparation of certain foods?
What is the role of fungi in the preparation of certain foods?
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Which structural feature is characteristic of fungal cells?
Which structural feature is characteristic of fungal cells?
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How do yeasts primarily reproduce?
How do yeasts primarily reproduce?
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What is the body structure of a fungus known as?
What is the body structure of a fungus known as?
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What defines coenocytic hyphae in fungi?
What defines coenocytic hyphae in fungi?
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What is the primary function of hyphae in fungi?
What is the primary function of hyphae in fungi?
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Which of the following diseases can fungi cause?
Which of the following diseases can fungi cause?
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What is a unique feature of the mycelium formed by molds?
What is a unique feature of the mycelium formed by molds?
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Study Notes
Fungi: Key Roles in the Environment and Industry
- Fungi break down complex organic materials (like dead plants and animals) into simpler compounds, playing a crucial role in nutrient cycling.
- They are a major cause of disease in plants, invading leaves through openings called stomata.
- Fungi also cause diseases in animals and humans.
- Yeasts, a type of fungi, are essential for fermentation processes like making bread, wine, and beer.
- Fungi are involved in the production of various foods like cheeses, soy sauce, and sufu.
- Fungi are vital for commercial production of organic acids (citric and gallic acids) and certain drugs like ergometrine and cortisone.
- Fungi are important in the production of antibiotics (penicillin, griseofulvin) and the immunosuppressive drug cyclosporin.
Fungal Structures
- The fungal body, also known as the thallus, varies in structure and size, ranging from single-celled yeasts to multicellular molds, puffballs, and mushrooms.
- Typically, fungal cells have a cell wall made of chitin, a strong and flexible polysaccharide composed of N-acetylglucosamine residues.
Yeasts
- Yeasts are single-celled fungi with a single nucleus.
- They reproduce by budding (asexual) and spore formation (sexual).
- Each bud that separates can develop into a new yeast cell.
- Yeast cells are generally spherical or egg-shaped and lack flagella but contain most eukaryotic organelles.
Molds
- Mold thalli consist of long, branched, thread-like filaments called hyphae, which form a tangled mass known as mycelium.
- Some fungi have hyphae without cross-walls, called coenocytic or aseptate hyphae.
- Other fungi have cross-walls, called septa, with pores that allow cytoplasmic streaming. These hyphae are called septate hyphae.
- Hyphae are composed of an outer cell wall and an inner lumen, which contains the cytosol and organelles.
- The filamentous nature of hyphae provides a large surface area for efficient nutrient absorption.
Dimorphic Fungi
- Many fungi, especially those causing diseases in humans and animals, are dimorphic, meaning they exist in two forms.
- Dimorphic fungi can switch between a yeast form (in the animal) and a mold/mycelial form (in the external environment) in response to environmental changes (nutrients, CO2, temperature). This shift is called the YM shift.
Fungal Nutrition and Metabolism
- Fungi thrive in dark, moist habitats with abundant organic material.
- Most fungi are saprophytes, obtaining nutrients from dead organic matter.
- They are chemoorganoheterotrophs, using organic compounds for carbon, electrons, and energy.
- Glycogen is the primary storage polysaccharide in fungi.
- Fungi generally use carbohydrates (glucose or maltose) and nitrogenous compounds for synthesizing amino acids and proteins.
- Many fungi are aerobic, but some yeasts are facultatively anaerobic, meaning they can ferment to obtain energy. Obligately anaerobic fungi are found in the rumen of cattle.
- Fungal fermentations are crucial in industrial processes, such as ethanol production for beer and wine.
Fungal Ecology
- Along with bacteria, fungi are major decomposers in the biosphere, responsible for breaking down organic matter.
- Fungi are unique in their ability to break down cellulose and lignin, complex plant components.
- Fungi form symbiotic relationships with various organisms:
- Obligate symbiosis: Essential for fungal survival.
- Facultative symbiosis: Not essential for fungal survival.
Types of Symbiotic Relationships
- Pathogens and parasites: Benefit at the expense of the host.
- Commensals: Benefit one partner but do not harm or benefit the other.
- Mutualistic relationships: Benefit both partners.
Endophytic Fungi
- Endophytic fungi live inside the intercellular spaces of plants.
- They can protect their host from herbivores by producing toxins, making the host less palatable to herbivores.
- Ryegrass is more resistant to aphid feeding in the presence of endophytes.
Lichens
- Lichens represent a symbiotic relationship between a specific ascomycete fungus and either green algae or cyanobacteria.
Fungal Preservation Techniques
- Stock cultures are transferred to fresh media at intervals and stored at 4°C to preserve their viability.
- Agar slants are commonly used, but contamination must be avoided.
- Long-term preservation methods aim to maintain the viability and genetic stability of fungal cultures.
- Preservation methods can be categorized into two groups:
- Metabolically inactive:
- Cryopreservation: Freezing cells or tissues at very low temperatures (-196°C).
- Drying methods: Spin freeze-drying, vacuum drying.
- Metabolically active:
- Culturing at low temperatures.
- Storage in liquid nitrogen.
- Cryoprotectant agents.
Mycotoxins
- Mycotoxins are toxic secondary metabolites produced by certain fungi.
- Mycotoxins can contaminate food and feed, posing risks to human and animal health.
- Rot disease in peanuts is caused by Aspergillus niger.
- Aspergillus species produce aflatoxin B1, a potent carcinogen associated with liver cancer.
Importance of Fungi
- Pharmaceuticals: Production of antibiotics (e.g., penicillin) and enzymes.
- Agriculture: Biopesticides (e.g., Bt cotton), biofertilizers, and biocontrol agents.
Protozoa: Key Features and Reproduction
- Protozoan cells contain at least one eukaryotic nucleus.
- Many protozoans have multiple nuclei, like ciliates.
- Ciliates have two distinct nuclei: a large macronucleus (controls metabolism and regeneration) and a small micronucleus (involved in reproduction).
- Reproduction in protozoa is primarily asexual.
- Many can also reproduce sexually.
- Parasitic protozoa may have an asexual phase in one host and a sexual phase in another (e.g., Plasmodium).
Asexual Reproduction in Protozoa
- Binary fission: Simple cell division.
- Multiple fission: Division into multiple daughter cells.
- Budding: Formation of buds that detach and grow.
Sexual Reproduction in Protozoa
- Involves the fusion of two gametes.
- Conjugation occurs in ciliates.
Control of Microorganisms
- Physical, chemical, and biological methods are used to inhibit or prevent microbial growth.
- Physical methods: Heat, radiation, filtration.
- Chemical agents: Disinfectants, antiseptics, antibiotics.
- Biological agents: Bacteria, fungi, viruses.
- Antimicrobial activity is influenced by factors like:
- Concentration of the agent.
- Temperature.
- pH.
- Presence of organic matter.
Mechanisms for Acquiring Resistance
- Microorganisms can develop resistance to antimicrobial agents through various mechanisms:
- Mutation: Changes in the microbial DNA.
- Horizontal gene transfer: Sharing of resistance genes between microbes.
- Reduced permeability: Altered cell membrane prevents drug entry.
- Drug inactivation: Production of enzymes that break down or modify the drug.
- Target modification: Alteration of the drug's target site within the microbe.
MRSA (Methicillin-resistant Staphylococcus aureus), VRSA (Vancomycin-resistant S. aureus), and VRE (Vancomycin-resistant Enterococcus)
- MRSA, VRSA, and VRE are clinically significant antibiotic-resistant bacteria.
- They are resistant to multiple antibiotics, including methicillin and vancomycin.
- MRSA and VRSA harbor several resistance genes, including those on plasmids which can transfer to other bacteria.
- VRE, particularly Enterococcus faecalis, accounts for a significant proportion of vancomycin-resistant bacteria.
- Clostridium difficile is a superinfection pathogen that can establish itself in the intestinal tract after antibiotic therapy.
- C. difficile is resistant to antibiotics, making infections difficult to treat.
Guidelines for Extending the Useful Life of Antimicrobials
- To combat the rising threat of antimicrobial resistance, guidelines are implemented for:
- Appropriate use: Prescribing antibiotics only when necessary.
- Complete courses: Finishing entire antibiotic regimens to ensure eradication of the infection.
- Infection prevention: Implementing measures to prevent the spread of infections.
- Development of new drugs: Researching and developing new antimicrobial agents to overcome resistance.
Antifungal Agents
- Human fungal infections have significantly increased in recent years.
- Fungal infections are more challenging to treat than bacterial infections due to:
- Slow growth: Fungi grow slower than bacteria.
- Tissue penetration: Fungal infections often occur in tissues difficult for antimicrobial agents to reach.
- Prolonged treatment: Therapy for fungal infections typically requires extended treatment.
- Antifungal agents target fungal-specific components:
- Chitin: Fungal cell walls contain chitin, which is absent in human cells.
- Ergosterol: Fungal cell membranes contain ergosterol, which is distinct from cholesterol in human cell membranes.
Fungal Infections
-
Two major categories of fungal infections:
- **Superficial:** Affecting the skin, hair, or nails: -
Dermatomycoses: Caused by fungi like Epidermophyton, Trichophyton, and Microsporum.
-
Candidiasis (yeast infections) : Caused by the genus Candida, affecting skin, mouth, GI tract, or vagina.
- **Systemic:** Impacting internal organs and systems: -
Candidiasis, Cryptococcosis, Aspergillosis, Blastomycosis, Histoplasmosis, Coccidioidomycosis, Paracoccidioidomycosis, etc.
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Description
Explore the critical roles fungi play in nutrient cycling, fermentation, and disease. This quiz covers various aspects of fungal structures and their importance in food production and pharmaceuticals. Test your knowledge on how fungi impact ecosystems and human industry.
