Introduction to Microbiology
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Questions and Answers

Which type of pathogen is primarily responsible for causing diseases in healthy individuals without predisposing conditions?

  • Chronic pathogen
  • Opportunistic pathogen
  • True pathogen (correct)
  • Environmental pathogen

Which component is characteristic of Gram-negative bacteria as opposed to Gram-positive bacteria?

  • Teichoic acid
  • Outer membrane (correct)
  • Thick peptidoglycan layer
  • Lipoteichoic acid

What is a key characteristic of virulence factors exhibited by pathogenic bacteria?

  • They are always present in non-pathogenic strains.
  • They enhance the bacteria’s ability to cause disease. (correct)
  • They are generally beneficial to host cells.
  • They prevent bacterial transmission.

Which of the following roles do microbes play in human health?

<p>Vaccine development (B)</p> Signup and view all the answers

Which attribute is NOT typically associated with the pathogenicity of a microorganism?

<p>Antibiotic resistance (C)</p> Signup and view all the answers

Which of the following describes a characteristic of endotoxins?

<p>They are part of the bacterial cell wall structure. (D)</p> Signup and view all the answers

What is a defining feature of virulence factors?

<p>They can become inactive through mutations in the bacterial genome. (A)</p> Signup and view all the answers

Which mechanism of bacterial virulence involves avoiding removal by the immune system?

<p>Evasion of phagocytic and immune clearance (A)</p> Signup and view all the answers

Which of the following structures is associated with bacterial adhesion?

<p>Pili (D)</p> Signup and view all the answers

What is the function of the lipid envelope in some viruses?

<p>It protects the viral genome and aids in entry into host cells. (A)</p> Signup and view all the answers

Which type of viral symmetry is characterized by a lipid bilayer and glycoprotein spikes?

<p>Enveloped icosahedral (B)</p> Signup and view all the answers

Which of the following classifications does not include DNA viruses?

<p>Retroviridae (D)</p> Signup and view all the answers

What is the primary structural component of fungal cell walls?

<p>Chitin (A)</p> Signup and view all the answers

Which of these viruses is classified as a double-stranded DNA virus?

<p>Hepatitis B Virus (B)</p> Signup and view all the answers

Which type of virus does not have a lipid envelope?

<p>Picornaviridae (B)</p> Signup and view all the answers

In which structure do fungi grow as branching, interlacing filaments?

<p>Mycelium (B)</p> Signup and view all the answers

What type of hyphae has perforated cross-walls?

<p>Septate hyphae (C)</p> Signup and view all the answers

Which of the following viruses is classified as an enveloped virus?

<p>Hepatitis B Virus (D)</p> Signup and view all the answers

Which type of RNA virus is characterized by having a positive-sense single-stranded RNA?

<p>Caliciviridae (B)</p> Signup and view all the answers

Which of the following best describes a non-septate hypha?

<p>Has multiple nuclei in one cell (B)</p> Signup and view all the answers

Flashcards

Pathogenicity

The ability of a microorganism to cause disease.

Pathogen

A microorganism capable of causing disease.

Gram-positive bacteria

Bacteria with a thick peptidoglycan layer in their cell walls, which stains purple by Gram stain.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer in their cell walls, surrounded by an outer membrane and which stains pink by Gram stain.

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True pathogen

A pathogen that can cause disease in a healthy individual.

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What are virulence factors?

Virulence factors are bacterial components that contribute to the pathogenicity of a microorganism. They increase the ability of a bacteria to cause disease.

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What's the difference between exotoxins and endotoxins?

Exotoxins are toxic substances secreted by bacteria, while endotoxins are components of the bacterial cell wall, mainly associated with Gram-negative bacteria, that are released upon the bacteria's death.

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How does a capsule help bacteria evade the immune system?

A capsule is a protective outer layer of polysaccharides that surrounds some bacteria. It prevents phagocytosis, the process by which immune cells engulf and destroy bacteria.

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What are the molecular postulates of microbial pathogenesis?

A set of criteria used to establish a causal relationship between a microbe and a disease. It involves identifying a virulence factor, showing how the pathogen becomes less virulent with mutations, and demonstrating how the pathogen can transfer its pathogenicity to a non-pathogenic organism.

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What is a virus?

A virus is a tiny infectious agent composed of genetic material (DNA or RNA) enclosed in a protein coat, sometimes with a lipid envelope, that can only replicate inside living cells.

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What is a virus's host range?

The range of organisms that a particular virus can infect. It is determined by the virus's ability to attach to, enter, and replicate within the host's cells.

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What is a virus's cell surface receptor?

A specific protein or molecule on the surface of a host cell that a virus binds to. It allows the virus to attach and enter the cell.

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What are the 5 basic types of viral symmetry?

Five main shapes for viral capsids: Icosahedral, Enveloped Icosahedral, Helical, Enveloped Helical and Complex.

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What is an icosahedral capsid?

A viral capsid with a 20-sided geometric symmetry, resembling a soccer ball.

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What is an enveloped icosahedral capsid?

An icosahedral capsid surrounded by a lipid membrane, called an envelope.

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What is a helical capsid?

A viral capsid shaped like a long, hollow cylinder, like a spring.

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What is an enveloped helical capsid?

A helical capsid surrounded by a lipid membrane, like an enveloped icosahedral capsid.

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What is a complex capsid?

Viral capsids that don't fit into the other categories, often with more complex shapes and structures.

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What are fungi?

Non-photosynthetic eukaryotic organisms that can exist as single-celled yeasts or as a mass of branching filaments called hyphae.

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What is a mycelium?

A network of branching, interlacing hyphae that forms the body of a multicellular fungus.

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Study Notes

Introduction to Microbiology

  • Microbiology is the study of microorganisms, which includes bacteria, viruses, fungi, and parasites.
  • Microorganisms can cause disease, but many are beneficial.
  • Microorganisms are used to create vaccines and in gene therapy.
  • They are also important in normal flora and nutritional processes.

Outline

  • Role of microbes in humans
  • Pathogenicity and routes of infection
  • Mechanisms of bacterial virulence
  • Bacterial morphology
  • Gram staining properties
  • Virulence factors
  • Viruses as disease-causing agents
  • Fungi as disease-causing agents

Role of Microbes in Humans

  • Beneficial: Helpful functions
  • Nutritional: Provide nutrients
  • Normal flora (especially bacteria): Living in the body
  • Vaccine development: Manufacturing vaccines
  • Gene therapy: Tool for gene therapy
  • Investigative tools: Helpful in investigation
  • Disease-causing agents: Causing diseases

Pathogenicity

  • Attributes of pathogenicity: Characteristics of a disease-inducing pathogen
  • Transmissible: Ability to spread/transfer
  • Infectivity: Ability to enter and multiply in host
  • Virulence: Ability to cause widespread damage
  • Exogenous & endogenous infection: Infections coming from external & internal sources respectively

Sites and routes of microbial infection

  • Respiratory tract
  • Mouth
  • Conjunctiva
  • Anus
  • Urogenital tract
  • Alimentary tract
  • Skin
  • Scratches/injury
  • Arthropod
  • Capillary

Pathogen (disease)

  • Pathogen: microorganism that causes disease
  • Two types of pathogens:
    • True pathogens: Always cause disease
    • Opportunistic pathogens: Cause disease only under certain conditions

Role of Bacteria in Disease

  • Prokaryote: Single-celled organism lacking a nucleus and membrane-bound organelles
  • Cell wall: Rigid layer surrounding the cell
  • Peptidoglycan: Principal component of bacterial cell wall
  • Flagellum: Whip-like structure that enables movement

Bacterial Morphology

  • Shapes of bacteria:
    • Coccus: spherical
    • Bacillus: rod-shaped
    • Coccobacillus: short rod-shaped
    • Spirillum: spiral-shaped
    • Vibrio: comma-shaped
    • Spirochete: long, spiral-shaped

Gram Stain

  • Gram-positive: Bacteria retain crystal violet stain, appear purple
  • Gram-negative: Bacteria lose crystal violet stain, appear pink

Bacterial Membrane Structures

  • Cell wall Gram-positive bacteria
    • Peptidoglycan: Glycan chain of GlcNAc & MurNAc
    • Teichoic acid: polymer of ribitol or glycerol
    • Lipoteichoic acid: Lipid-linked teichoic acid
  • Cell wall Gram-negative bacteria
    • Peptidoglycan: Thinner than gram-positive
    • Outer membrane: Contains phospholipids and proteins
    • Periplasmic space: Space between the inner and outer membranes
    • LPS: Lipid A, core polysaccharide, O antigen

Classification of Gram stainable pathogens

  • Bacteria are classified based on various factors including Gram stain properties, genus, and species-examples are listed based on these factors.

Molecular Postulates

  • Virulence factors: Attributes associated with causing disease (only in pathogenic strains)
  • Mutation: Organisms can become less virulent
  • Transfer to a non-pathogenic organism: It can become pathogenic
  • Immune response: A protective reaction from the host organism

Mechanisms of Bacterial Virulence

  • Adherence (sticking)
  • Invasion: (entering and multiplying)
  • By-products of growth (e.g., gas, acid)
  • Toxins (harmful substances)
  • Degradative enzymes (breaking down tissues)
  • Cytotoxic proteins (killing cells)
  • Endotoxin
  • Superantigen
  • Induction of excess inflammation Evasion of phagocytic and immune clearance
  • Capsule (protective barrier)
  • Resistance to antibiotics
  • Intracellular growth

Tissue Injury

  • Toxins: Damage to tissues
    • Exotoxins: Specific immunity (antigen)-based damaging substances
    • Endotoxins: Non-specific damaging substances.

What Are Viruses?

  • Viruses: Organized associations of macro-molecules
  • Nucleic acid: Blueprint for replication
  • Progeny virions: New virus particles
  • Protective shell: Protein units

What Are Viruses? (continued)

  • Nucleic acid genome: DNA or RNA
  • Protein coat: Protection and entry
  • Lipid envelope: Present in some viruses
  • Small: 20-400nm
  • Obligate intracellular parasites: Depend on host cells for replication

Virus particle (virion)

  • DNA Viruses: Examples are listed.
  • RNA Viruses: Examples are listed.

Host Range

  • Cell surface receptor: Allows viruses to attach and enter cells
  • Ability to get out of cell and spread
  • Host anti-viral response: Defense mechanisms of the host

Viral Symmetry

  • Icosahedral, enveloped icosahedral, helical, enveloped helical, complex

DNA Viruses/RNA viruses

  • Classification based on strandedness, enveloped/non-enveloped, and shape.

Viruses: Images

  • Various viruses are shown in images

Fungi

  • Fungi: Non-photosynthetic protists
  • Grow as single-celled yeasts or mass of branching, interlacing filaments (hyphae)/mycelium
  • Hyphae have perforated cross-walls (septate) or no cross-walls (coenocyte)
  • Cell wall of the tube is made of chitin

Fungi: Images

  • Illustrations of septate hyphae and yeasts.

Mycotic Diseases

  • Hypersensitivity (allergy)
  • Mycotoxicosis (toxin production)
  • Mycetismus (mushroom poisoning)
  • Infection (invasion of tissues)

Laboratory methods in fungal identification

  • Wet mount (Lactophenol cotton blue, KOH)
  • Staining (Giemsa, mucicarmine, Calcoflour white stain, Gram, PAS)
  • Fluorescent monoclonal antibody
  • Skin test
  • Biopsy & histopathology (GMS, H&E)
  • Serology
  • Culture
  • DNA probes

Human mycotic infections

  • Superficial mycoses
  • Cutaneous mycoses
  • Subcutaneous mycoses
  • Deep or systemic mycoses: Examples shown

Molds: Penicillium species

  • Images illustrating molds.

Candida

  • Images illustrating Candida.

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Description

Explore the fascinating world of microbiology, focusing on the diverse roles of microorganisms in human health and disease. This quiz delves into beneficial microbes, pathogenicity, and the mechanisms that enable bacteria and viruses to cause illness. Test your knowledge on the impacts of these tiny organisms on vaccines, gene therapy, and nutritional processes.

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