Microbiology Chapter on Immunity and Resistance
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Questions and Answers

What is primarily responsible for the immune response to an invading organism?

  • Hormones
  • Enzymes
  • Antigens (correct)
  • Vitamins

    • What mechanism allows bacteria to develop resistance through spontaneous changes in their DNA?

  • Spontaneous mutation (correct)
  • Conjugation
  • Transformation
  • Transduction

    • Which characteristic of an antigen enhances the immune system's recognition of it?

  • It is biochemically similar to the host.
  • It is present in the host's cells.
  • It is biochemically very different from its host. (correct)
  • It is located in the nuclear membrane.

    • Which enzyme is commonly associated with resistance to penicillin?

    <p>Penicillinase</p> Signup and view all the answers

    How do normal flora contribute to immunity?

    <p>They make the environment inaccessible to pathogens.</p> Signup and view all the answers

    In the tube dilution method of antibiotic sensitivity testing, what does a lower dilution of an antibiotic indicate?

    <p>Higher effectiveness</p> Signup and view all the answers

    What could be a result of a compromised normal flora population?

    <p>Successful pathogen invasion.</p> Signup and view all the answers

    What role do R factors play in bacteria?

    <p>They provide antibiotic resistance</p> Signup and view all the answers

    Which substance do normal flora produce that aids in defending against pathogens?

    <p>Glycoprotein and polysaccharide molecules</p> Signup and view all the answers

    What method involves the transfer of genetic material through a mating bridge between two bacteria?

    <p>Conjugation</p> Signup and view all the answers

    What kind of immunity is exemplified by the function of normal flora?

    <p>Innate immunity</p> Signup and view all the answers

    What is a notable benefit of identifying an organism’s antigenic structure?

    <p>It can lead to the development of targeted vaccines.</p> Signup and view all the answers

    What does the disk method of antibiotic sensitivity testing show when bacteria are resistant?

    <p>Continued growth near the disk</p> Signup and view all the answers

    Which treatment was shown to be more effective than antibiotics in C difficile infections?

    <p>Probiotics</p> Signup and view all the answers

    What type of DNA is found in plasmids?

    <p>Circular DNA</p> Signup and view all the answers

    Which process allows bacteria to take up free DNA from their environment?

    <p>Transformation</p> Signup and view all the answers

    What is the main characteristic of the lytic viral replication cycle?

    <p>The host cell is destroyed after viral duplication.</p> Signup and view all the answers

    In which viral replication cycle does the viral DNA become a part of the host's DNA?

    <p>Lysogenic cycle</p> Signup and view all the answers

    What triggers the lysogenic virus to switch to the lytic cycle?

    <p>Environmental factors</p> Signup and view all the answers

    Which structure is NOT commonly found in viruses?

    <p>Nuclear membrane</p> Signup and view all the answers

    What is the role of viral proteins during the lytic cycle?

    <p>To bind to receptors on target cells</p> Signup and view all the answers

    What occurs as a result of viral activation in a lysogenic cycle?

    <p>The host cell becomes a viral factory.</p> Signup and view all the answers

    Which viral component is responsible for the genetic information of the virus?

    <p>DNA interior</p> Signup and view all the answers

    Which of the following best describes a characteristic of the lysogenic cycle?

    <p>The virus can be dormant for long periods.</p> Signup and view all the answers

    What is the basic life cycle sequence of bacteria?

    <p>Grow, Replicate DNA, Divide, Repeat</p> Signup and view all the answers

    Which factor does NOT limit bacterial growth?

    <p>Enhanced RNA synthesis</p> Signup and view all the answers

    Bacteria can be classified based on which of the following characteristics?

    <p>Shape and arrangement</p> Signup and view all the answers

    A typical pattern of bacterial multiplication leads to reaching what is known as:

    <p>Carrying capacity</p> Signup and view all the answers

    The two basic models for viral life cycles are referred to as:

    <p>Lytic and lysogenic</p> Signup and view all the answers

    Bacteria lack which of the following structures?

    <p>Nucleus</p> Signup and view all the answers

    What classification criteria includes the terms coccus and bacillus?

    <p>Shape and arrangement</p> Signup and view all the answers

    Which of the following describes a characteristic of gram-negative bacteria?

    <p>They often appear red or pink after staining.</p> Signup and view all the answers

    What is the significance of lactobacilli in maintaining vaginal health?

    <p>They produce an acid that helps inhibit the growth of infections.</p> Signup and view all the answers

    What indicates a shift towards bacterial vaginosis?

    <p>An overgrowth of coccobacilli.</p> Signup and view all the answers

    Which of the following is a characteristic of obligate pathogens?

    <p>They never contribute to normal health.</p> Signup and view all the answers

    What can lead to the overgrowth of yeast in the vagina?

    <p>A shift in vaginal pH to above 4.5.</p> Signup and view all the answers

    What is passive acquired immunity?

    <p>Temporary immunity achieved through borrowed antibodies.</p> Signup and view all the answers

    Which of the following contributes to nonspecific immunity?

    <p>Physical barriers such as skin and mucous membranes.</p> Signup and view all the answers

    What happens when the lactobacilli population decreases?

    <p>Coccobacilli may become overrepresented.</p> Signup and view all the answers

    What can cause a decrease in lactobacilli populations?

    <p>Presence of pathogenic organisms or antibiotic use.</p> Signup and view all the answers

    What is a characteristic of the lysogenic cycle?

    <p>Viral DNA is inserted into the host chromosome.</p> Signup and view all the answers

    How can uncontrolled cell growth related to viral infections occur?

    <p>When viruses insert themselves in genes controlling cell division.</p> Signup and view all the answers

    Which of the following is NOT a feature of RNA viruses?

    <p>They insert viral DNA into the host chromosome directly.</p> Signup and view all the answers

    Which of the following statements about the lytic cycle is correct?

    <p>Host cell components are used to produce viral particles.</p> Signup and view all the answers

    HPV and HIV are examples of viruses that can cause what?

    <p>Uncontrolled cell growth linked to cancer.</p> Signup and view all the answers

    What is the term for viral DNA that has integrated into the host genome?

    <p>Provirus</p> Signup and view all the answers

    Which of the following is a common method for the release of new viral particles from an infected cell?

    <p>Shedding or bursting of the host cell.</p> Signup and view all the answers

    What role does reverse transcriptase play in some RNA viruses?

    <p>It converts RNA to DNA.</p> Signup and view all the answers

    Study Notes

    DPAS 5200A25 Day 3: Introduction to Bacteria and Viruses

    • The class covered infectious agents and their basic introduction.
    • Introductory material included an inspirational presentation for the study of infectious agents to spark interest.
    • Today's focus was on bacteria and virus physiology, covering objectives for the two-day session.

    Objectives for Day 2: Bacteria/Virus Physiology

    • Describe the structures of bacteria and viruses.
    • Translate bacteriological nomenclature.
    • Classify bacteria into their subgroups.
    • Understand the role of normal flora in preventing infection.
    • Explain the terms and concepts of specific, nonspecific immunity, host immunity, virulence, and mutability in the context of pathogenicity.
    • Understand the lytic and lysogenic cycles of viral replication.
    • Explain how bacteria and viruses cause infection.

    Bacterial Life Cycle

    • Bacteria are prokaryotes without membrane-bound organelles such as the nucleus, ER, or Golgi.
    • The bacterial life-cycle is simple, characterized by growth-DNA replication-division-and repetition.

    Bacterial Reproduction

    • Many bacteria replicate every 20 minutes exponentially.
    • A single bacterium could theoretically cover the globe in 24 hrs if conditions permit.
    • However, bacterial reproduction is limited by resource availability, environmental conditions, predators, and defense mechanisms (the immune systems).

    Bacterial Classification

    • Bacteria are grouped by criteria like shape and arrangement, gram stain reaction (gram-positive and gram-negative), and biochemical characteristics (aerobic and anaerobic species). There's also spore formation profile, and antigenic structure analysis like in cell bodies, capsule, and flagella.

    Classification of Bacteria: Human Correlations

    • Bacteria are grouped according to their likeness to humans, such as skin color differentiation or hair color/amount, language background, diet preferences (omnivore, vegetarian, vegan), tolerance to heat, and burn-related tolerance versus tanning-related tolerance.
    • This is different from the more scientific classification methods mentioned previously.

    Bacterial Growth Preferences

    • Bacteria have varying preferences for growth media and environmental conditions, classifying as fastidious or hardy organisms based on their preference.
    • Fastidious bacteria require enriched media with specialized conditions like precise temperature, and acidity to thrive.
    • Hardy bacteria are resilient and thrive in a wide range of environmental conditions.
    • Other key criteria for their classifications are oxygen requirements, in which there are aerobic, anaerobic and facultative anaerobic species.

    Structural Features of Bacteria

    • Flagella (hair-like processes) aid in bacterial motility.
    • Spore formation (dormant, resilient structures) allows bacteria to survive under harsh conditions until favorable conditions return.
    • Recognition of the formation of spores or flagella may give insight into identification.

    Antigenic Structure

    • Antigens are unique components of an invading organism that stimulate antibody production in mammals.
    • These antigens are usually parts of the bacterial cell body, capsule, wall, or flagellum, triggering an immune response as 'not-you'.
    • A biochemical difference between the organism and its host will make specific parts of the organism antigens.

    Symbiotic Relationships Between Humans and Bacteria

    • Symbiotic interactions can be categorized as mutualism (benefits both), commensalism (benefits one, no harm to the other), or opportunistic (harmless then harmful).
    • Symbiotic relationships with humans, where bacteria benefit the human and/or cause no harm, can even benefit.

    Normal Flora

    • Normal flora are microorganisms that colonize the human body (such as the GI tract) without causing harm; rather, they aid in immune system development.
    • Flora establishment in humans begins shortly post-birth.
    • Normal flora perform metabolic functions and contribute to immunity.

    Normal Flora and maintaining "Peri-human" health

    • Normal flora create a protective layer (glycoprotein and polysaccharide molecules, the mucosal layer).
    • This layer stops pathogens from entering the body.
    • The presence of normal flora needs to be maintained to protect the body.

    Maintaining Healthy Normal Flora

    • Ensuring a healthy normal flora population is crucial for preventing bacterial overgrowth.
    • Treatments for diseases like C. difficile can be illustrated using three different treatments for C diff.

    Normal vs. Overpopulation

    • "Normal" also encompasses the absence of overpopulation of specific bacteria.
    • This applies to various areas of the body, such as the vaginal area.
    • Overpopulation of normal bacterial types can be problematic.
    • Example: Normal vaginal flora vs bacterial vaginosis.

    Bacterial Vaginosis

    • Lactobacilli produce acid that maintain a vaginal pH of 3.8-4.2.
    • Decrease in lactobacilli population can shift vaginal pH to over 4.5.
    • This shift can lead to overgrowth of harmful bacteria, yeast overgrowth, or environmental factors leading to more pathogenic overgrowths.

    Obligate Pathogens

    • Obligate pathogens are always harmful and never normal findings in a healthy person.
    • Examples mentioned include Lyme disease, Toxic Shock, Food Poisoning, and Cholera.

    Human Immunity

    • Human immunity includes both nonspecific and specific (acquired) components.
    • Nonspecific immunity involves innate defenses like skin, pH levels in organs, and compartmentalization, as well as inflammation and normal flora.
    • Specific immunity involves specialized responses targeted toward particular pathogens (details in Pathophysiology).

    Acquired immunity

    • Passive immunity involves antibodies that are obtained from an exterior source like another organism (not produced by your body).
    • This immunity is temporary and not long-term because antibodies have a limited life span.
    • Active immunity occurs when the body creates its own antibodies in response to a vaccine or an encountered pathogen.

    Antibiotics

    • Antibiotics come from living organisms and/or lab-synthesized formulas, with resistance issues stemming from over-prescribing, inappropriate use, overuse in livestock feed, and widespread resistance propagation.
    • Antibiotics work by inhibiting bacterial cell wall and membrane synthesis; inhibiting bacterial protein synthesis; inhibiting bacterial reproduction, and turning off bacterial enzymes.

    Antibiotic Resistance mechanisms

    • Resistant strains develop through spontaneous mutation, plasmid transfer (conjugation and transformation), and the development of enzymes (like penicillinase) that degrade antibiotics.
    • Testing for antibiotic sensitivity to diagnose bacterial infections can be done using procedures like tube dilution (measuring highest inhibition) or disk diffusion (seeing the inhibition zone around placed antibiotic disks on a microbial lawn).

    Plasmids and Resistance

    • Plasmids are small, circular DNA molecules separate from the bacterial chromosome.
    • Some plasmids carry genes (like the F-factor) facilitating conjugation (transferring genes between bacteria).
    • Others (R-factors) can code for antibiotic resistance genes, also transferred via conjugation or transformation.

    Bacterial Conjugation

    • A process where bacteria can exchange genetic material (including plasmids, possibly containing antibiotic resistance genes).

    Bacterial Transformation

    • Bacteria may absorb stray DNA from their environment and integrate it into their own genetic material using endocytosis.

    Viral Life Cycles

    • Viruses can have lytic or lysogenic cycles.
    • Viral replication depends on host cells for machinery and components.

    Lytic Viral Replication

    1. Attachment
    2. Entry
    3. Replication
    4. Assembly
    5. Release

    Lysogenic Viral Replication

    1. Attachment
    2. Entry
    3. Integration
    4. Cell Division/Reproduction
    5. Induction
    6. Replication
    7. Assembly
    8. Release

    Lytic versus Lysogenic Viral Systems Summary

    • Lytic viral replication involves the release of many viral particles, destroying the host cell in the process.
    • Lysogenic viral replication involves the integration of viral genetic material into the host cell genome with the viral genetic material being reproduced during the host cell's reproduction (e.g., prophage or provirus).

    RNA Viruses

    • RNA viruses lack a "proofreader" during replication; hence, mistakes during RNA synthesis (leading to mutations) are often left uncorrected.
    • These RNA viruses often mutate rapidly and therefore evolve easily to be more pathogenic (cause more disease).
    • RNA viruses, like HIV, have a specific mechanism of DNA synthesis through reverse transcriptase and may have both lytic and lysogenic life cycles.

    COVID-19

    • A single-stranded RNA virus that has a high mutation rate is often linked to the spike protein.

    HIV: A Retrovirus

    • HIV is a Retrovirus, a virus with an RNA genome that uses reverse transcriptase to synthesize DNA from its RNA genome.
    • It has a lysogenic cycle. The acute phase and chronic phase of infection are characterized by different stages of viral reproduction and CD4 cell counts.

    Helper T Cells

    • Helper T cells are critical for coordinating the immune response.
    • They activate cytotoxic T cells, B cells, and other immune cells.
    • Without Helper T cells, the immune response is severely compromised.

    HIV as an Emerging Virus

    • HIV, like other emerging viruses, is linked to mutations, contact between species, spread from isolated populations, and spread to overcrowding areas with poor sanitation (which increases exposure and decreases the immune system's ability to defend).

    Additional Viruses

    • Rhinovirus, Mumps, Influenza, Measles, and Chicken Pox were mentioned as additional viruses.

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    Test your knowledge on immunology and bacterial resistance with this quiz. Covering mechanisms of immune response, antibiotic sensitivity, and the role of normal flora, explore the intricate details of how bacteria evolve and how our immune system responds. Perfect for students of microbiology and related fields.

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