Microbiology Chapter on Tuberculosis and Immunity

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Questions and Answers

What type of organism is Mycobacterium tuberculosis, and what disease does it cause?

Mycobacterium tuberculosis is a bacterium that causes tuberculosis (TB).

Describe the role of tubercles in a tuberculosis infection.

Tubercles act as a protective seal around infected phagocytes, allowing the bacteria to remain dormant. This prevents the immune system from destroying the bacteria during the initial infection.

Identify two ways pathogens can enter the human body.

Pathogens can enter through inhalation and ingestion. Other methods include direct contact and vector transmission.

What are fomites and how can they contribute to the spread of pathogens?

Fomites are inanimate objects that can be contaminated with pathogens. They can transfer pathogens to skin, eyes, or mouth, leading to infections. Signup and view all the answers

Explain how the lambda phage structure differs from the shapes of viruses that infect humans.

The lambda phage has a unique structure characterized by a head, tail, and tail fibers, which is different from the shapes of viruses that infect humans and mammals. Signup and view all the answers

What happens to the immune system when it becomes weakened in relation to tuberculosis?

When the immune system weakens, Mycobacterium tuberculosis can become active, leading to damage in lung tissue. This results in symptoms such as coughing and breathing problems. Signup and view all the answers

In what ways can direct contact facilitate the spread of pathogens?

Direct contact can facilitate the spread of pathogens through skin-to-skin contact or bodily fluids. This is particularly significant for sexually transmitted infections. Signup and view all the answers

Name a common bacterial infection caused by ingestion of contaminated food.

Salmonella is a common bacterial infection contracted through consuming contaminated food. Signup and view all the answers

Where do B cells mature and what immune response are they involved in?

B cells mature in the bone marrow and are involved in the humoral response. Signup and view all the answers

What is the role of T helper cells in the immune response?

T helper cells stimulate B cells and T killer cells to divide, enhancing the immune response. Signup and view all the answers

What is meant by 'clonal selection' in the context of B effector cells?

Clonal selection refers to the process where B effector cells, or plasma cells, replicate their specific antibody upon encountering an antigen. Signup and view all the answers

How do memory cells contribute to long-term immunity?

Memory cells replicate when exposed to the same pathogen and remain in lymph nodes, allowing for a faster immune response upon reinfection. Signup and view all the answers

Describe the process that occurs when a T cell is activated.

Upon recognizing complementary antigens presented by an antigen-presenting cell, the T cell becomes activated and divides rapidly by mitosis. Signup and view all the answers

Differentiate between active and passive immunity.

Active immunity is when the body produces its own antibodies and memory cells, while passive immunity involves the transfer of antibodies from another individual. Signup and view all the answers

What is the function of T killer cells in the immune system?

T killer cells destroy pathogen-infected cells by creating holes in their cell surface membrane, causing them to burst. Signup and view all the answers

What occurs during the B cell response once they bind to antigens?

B cells digest the pathogen, present its antigens, and proliferate to produce plasma cells or memory cells. Signup and view all the answers

Describe the difference between natural active immunity and artificial active immunity.

Natural active immunity develops after catching an infection, while artificial active immunity develops after vaccination. Signup and view all the answers

What is the primary function of passive immunity?

Passive immunity provides immediate protection without the body producing antibodies against a pathogen. Signup and view all the answers

Explain how bactericidal antibiotics work.

Bactericidal antibiotics kill bacteria by destroying their cell wall, causing them to burst. Signup and view all the answers

What is the impact of antibiotic use on bacterial evolution?

Antibiotic use creates selection pressure, favoring the survival of bacteria with advantageous mutations for immunity. Signup and view all the answers

Define natural passive immunity and provide an example.

Natural passive immunity occurs when antibodies are passed from a mother to her baby, for example, through breast milk. Signup and view all the answers

How does HIV evade the immune system?

HIV has a high mutation rate, leading to changes in antigens that are not recognized by memory cells during reinfection. Signup and view all the answers

What role does the skin play in the body's defense against infection?

The skin acts as a tough physical barrier composed of keratin that prevents pathogens from entering the body. Signup and view all the answers

What mechanism do bacteriostatic antibiotics use to inhibit bacterial growth?

Bacteriostatic antibiotics inhibit bacterial growth by stopping protein synthesis and nucleic acid production. Signup and view all the answers

How does stomach acid contribute to the immune system?

Stomach acid, or hydrochloric acid, kills bacteria that enter the digestive tract, providing a chemical barrier against pathogens. Signup and view all the answers

Why is the evolutionary race between pathogens and host cells significant?

It highlights the ongoing struggle between evolving pathogens and the immune responses of host cells. Signup and view all the answers

What happens during inflammation as part of the non-specific immune response?

Inflammation occurs when tissue is damaged, releasing histamines that cause vasodilation and increase blood flow to the affected area. Signup and view all the answers

Explain the process of phagocytosis.

Phagocytosis is when a phagocyte engulfs a pathogen, isolating it in a phagocytic vesicle and digesting it with lysosomal enzymes. Signup and view all the answers

What is the function of interferons in the immune response?

Interferons are proteins that prevent viruses from spreading by inhibiting protein synthesis in infected cells. Signup and view all the answers

Describe the role of gut and skin flora in the body's defense.

Gut and skin flora compete with pathogens for resources, effectively preventing harmful bacteria from establishing themselves. Signup and view all the answers

What occurs when an antigen presenting cell activates other types of immune cells?

An antigen presenting cell displays the pathogen's antigens, prompting specific immune responses by activating T cells and B cells. Signup and view all the answers

How do lysozymes contribute to the immune response?

Lysozymes are enzymes that damage bacterial cell walls, effectively killing bacterial cells found in tears and mucus. Signup and view all the answers

What are the two types of cultures used for growing microorganisms?

Pure culture and mixed culture. Signup and view all the answers

Why is aseptic technique important in culturing microorganisms?

Aseptic technique prevents contamination, which can reduce the yield of the desired microorganism. Signup and view all the answers

What role do sterile equipment and cleaning surfaces with ethanol play in microbiology?

They help to eliminate unwanted microorganisms and maintain a contamination-free environment. Signup and view all the answers

Describe the difference between batch culture and continuous culture.

Batch culture is a closed system with nutrients added at the start, while continuous culture is an open system with nutrients added continuously. Signup and view all the answers

What happens to the yield of a desired microorganism if contamination occurs in a batch culture?

Only that single batch is lost. Signup and view all the answers

What is one advantage of batch culture compared to continuous culture?

Batch culture is easier to set up and maintain. Signup and view all the answers

Why might an open fermenter be beneficial for continuous culture?

It allows for the continuous addition of nutrients and removal of products for sustained growth. Signup and view all the answers

How does heating the air with a bunsen burner help in aseptic techniques?

It causes the air to rise, carrying away airborne microorganisms. Signup and view all the answers

What is the role of DNA polymerase in the polymerase chain reaction (PCR)?

DNA polymerase is the enzyme that synthesizes new DNA strands by adding complementary nucleotides to the existing template strand. Signup and view all the answers

Describe the process of denaturation in PCR.

Denaturation occurs when the reaction mixture is heated to 95 degrees Celsius, causing the hydrogen bonds between DNA strands to break and resulting in the separation of the strands. Signup and view all the answers

How does gel electrophoresis differentiate between DNA fragments?

Gel electrophoresis separates DNA fragments by size, with shorter fragments moving faster through the gel matrix in response to an electric current. Signup and view all the answers

Why are genetic fingerprints unique to each individual?

Genetic fingerprints are unique because they reflect variations in the number of variable number tandem repeats (VNTRs) present in an individual's DNA. Signup and view all the answers

What is the purpose of primers in the PCR process?

Primers are short sequences of nucleotides that bind to the target DNA strands, providing a starting point for DNA polymerase to begin synthesis. Signup and view all the answers

What happens during the annealing step of PCR?

During the annealing step, the temperature is lowered to allow the primers to bind to the complementary DNA strands that have separated. Signup and view all the answers

How many times is the cycle of denaturation, annealing, and extension typically repeated in PCR?

The cycle is usually repeated around 30 times to produce a sufficient amount of DNA for analysis. Signup and view all the answers

What ensures that DNA moves towards the positive electrode during gel electrophoresis?

DNA is negatively charged, which causes it to migrate towards the positive cathode when an electric current is applied. Signup and view all the answers

Study Notes

Culturing Microorganisms

Culturing microorganisms is crucial for experimental biology, ensuring aseptic technique (contamination-free environment) for pure or mixed cultures.
Aseptic techniques include:
- Sterilizing reusable equipment with ethanol and a Bunsen burner flame.
- Cleaning surfaces with ethanol.
- Using a Bunsen burner to remove contaminants from the air, or other heat sources.
Two types of culturing exist:
- Batch culture: In a closed fermenter, microorganisms and nutrients are added for a set time.
- Continuous culture: In an open fermenter, continuous additions of nutrients and removal of products occur.
Maximizing product yield involves maintaining optimal temperature, nutrient availability, and pH levels. Avoiding anaerobic conditions is important.

Measuring Microbial Growth

Growth can be monitored by:
- Cell Counts: Using a gridded slide to count cells, and scaling up for the overall volume.
- Dilution Plating: Creating serial dilutions and growing cultures on plates, then counting colonies to calculate original cell numbers.
- Mass: Centrifuging cultured liquid to form a solid pellet, and weighing to determine mass.
- Turbidity: Observing cloudiness to measure cell concentration; a spectrophotometer measures light transmission through the culture.

Bacterial Growth Curve

Lag Phase: Initial phase where microorganisms adjust to conditions before reproduction begins.
Log Phase: Exponential growth; cell numbers increase rapidly.
Stationary Phase: Growth rate slows or stops due to limiting nutrients or accumulation of waste products.
Death (Decline) Phase: Number of live cells declines, as environmental conditions become detrimental.

Bacteria and Viruses

Key differences:
- Bacteria have ribosomes and replicate through binary fission outside of a cell; viruses lack ribosomes and replicate inside a host cell, dependent on cellular machinery.
- Viruses are much smaller and simpler in structure than bacteria.
Viral Structure:
- Genetic material (DNA or RNA).
- Capsid (protein coat).
- Attachment proteins.
- Enzymes (e.g., reverse transcriptase in some viruses).

Viral Life Cycle

Lytic cycle: Virus replicates inside the host, causes cell lysis, and releases new viruses.
Lysogenic cycle: Viral DNA integrates into host DNA without immediate replication; viral replication occurs later, often triggered by external stimuli.

Key Examples

Ebola Virus: West African epidemic; transmitted by bodily fluids.
Tobacco Mosaic Virus (TMV): First discovered plant virus impacting chloroplasts; spreads by contact between plants.
HIV: Targets T helper cells; leads to AIDS (acquired immunodeficiency syndrome).
Lambda Phage: Bacteriophage infecting E. coli, with a head, tail, and tail fibers structure.
Tuberculosis (TB): Bacterial disease attacking lung phagocytes; inflammation leads to potential breathing problems.

Immunity

Physical barriers: Skin, stomach acid, gut microbiome prevent entry.
Non-specific response: Inflammation to damage; lysozyme action in secretions.
Specific response: T-lymphocytes (cell-mediated) and B-lymphocytes (humoral); producing antibodies and memory cells for faster and more effective responses to future infections.

Types of Immunity

Active Immunity: Body produces antibodies. Natural (infection) or artificial (vaccination).
Passive Immunity: Receiving antibodies from another source. Natural (maternal antibodies) or artificial (antibody injections).

Antibiotics

Bactericidal antibiotics: Kill bacteria by damaging cell walls.
Bacteriostatic antibiotics: Inhibit bacterial growth (e.g., by stopping protein synthesis).

Microbial Decomposition and Recycling

Microorganisms (bacteria and fungi) break down organic matter to release inorganic ions (nutrients) and return carbon to the environment (e.g., as CO2 during respiration).

Gene Technology

Polymerase Chain Reaction (PCR): Technique for amplifying DNA for further study and cloning. Includes denaturation, annealing and elongation steps.
Gel Electrophoresis: Separation of DNA fragments by size using an electric field, creating a DNA fingerprint.

Estimating Time of Death

Decomposition stages and associated organisms
Body temperature cooling.
Muscle rigidity (rigor mortis).
Forensic entomology (insect life cycle).
Extent of decomposition.

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Description

Test your knowledge on the organism Mycobacterium tuberculosis, its role in causing disease, and how the immune system responds. Explore various pathways of pathogen entry, types of immunity, and the significance of immune cells in infections. This quiz covers critical concepts in microbiology and immunology.