Spontaneous Generation & Germ Theory

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Questions and Answers

What did Spallanzani's experiment demonstrate regarding microbes in broth?

Sealing broth prevents microbial growth. (correct)

Boiling broth eliminates all potential life.

Microbes originate from the air.

Microbes can grow in sealed containers.

Which of the following statements accurately reflects Francesco Redi's experiment?

Maggots were a result of spontaneous generation.

Maggots appeared in all jars.

Maggots emerged from sealed jars.

Maggots were unable to grow on covered meat. (correct)

What was Ignaz Semmelweis known for in the context of disease prevention?

Developing a vaccine against smallpox.

Proposing the germ theory of disease.

Emphasizing the need for handwashing. (correct)

Tracing cholera outbreaks effectively.

John Snow made significant contributions to which field during his medical career?

Epidemiology Signup and view all the answers

What did John Tyndall discover regarding bacterial forms?

Bacteria exist in heat-stable and heat-sensitive forms. Signup and view all the answers

What was the purpose of Tyndallization in microbiology?

To sterilize liquids through intermittent heating. Signup and view all the answers

What was Paul Ehrlich's contribution to medicine?

Developing a treatment for syphilis. Signup and view all the answers

Which factor did Oliver Wendell Holmes emphasize in preventing disease transmission?

The significance of handwashing. Signup and view all the answers

What type of paralysis is associated with Botulinum toxin?

Flaccid paralysis Signup and view all the answers

Which toxin is produced by Clostridium difficile and leads to pseudomembranous colitis?

Toxin B Signup and view all the answers

What is the primary impact of coagulase produced by Staphylococcus aureus?

Prevents phagocytosis Signup and view all the answers

What is the main role of a sex pilus in conjugation?

To facilitate the transfer of nucleic acid between bacterial cells Signup and view all the answers

Which virulence factor is responsible for breaking down hyaluronic acid in tissues?

Hyaluronidase Signup and view all the answers

Which of the following statements about endotoxins is correct?

They are released when bacteria die. Signup and view all the answers

Which type of bacteria is generally more competent for transformation?

Gram-positive bacteria Signup and view all the answers

What condition is typically required for a bacterium to take up DNA during transformation?

The bacterium must be competent Signup and view all the answers

What condition is associated with toxic shock syndrome toxin (TSST) produced by Staphylococcus aureus?

Septic shock Signup and view all the answers

How does generalize transduction occur?

By random incorporation of bacterial DNA into phages Signup and view all the answers

Enterotoxins are primarily produced in which part of the body?

Intestine Signup and view all the answers

What is a potential outcome for a lysogenic phage when the bacterial cell experiences stress?

It can become virulent Signup and view all the answers

What happens to the bacterial DNA taken up during transformation?

It must recombine with the host's DNA Signup and view all the answers

What is a common effect of the toxin produced by S. aureus during toxic shock syndrome?

Decreased blood pressure Signup and view all the answers

What process involves the transfer of DNA through direct contact between two bacterial cells?

Conjugation Signup and view all the answers

What condition is often induced in bacteria to make them competent for transformation?

Subjecting them to starvation Signup and view all the answers

What type of immunity is characterized by the production of antibodies by B-cells?

Humoral Immunity Signup and view all the answers

Which class of immunoglobulin is known for being the most abundant in the blood and is capable of crossing the placenta?

IgG Signup and view all the answers

What is the primary role of T-cells in cell-mediated immunity?

Kill intracellular microbes Signup and view all the answers

Which method of microbial control involves the use of high heat and moisture?

Pasteurization Signup and view all the answers

What is a characteristic feature of IgM immunoglobulin?

It is the first antibody produced in response to an antigen. Signup and view all the answers

How does chemical microbial control typically act on microbial cells?

By denaturing their proteins Signup and view all the answers

Which microbial control method utilizes filtration?

Liquid membrane filter Signup and view all the answers

Which of the following best describes the function of antibodies?

They bind to antigens and neutralize their effects. Signup and view all the answers

What type of hemolysin causes complete lysis of red blood cells?

Beta Signup and view all the answers

What is the main effect of exfoliative toxin produced by Staphylococcus aureus?

Sloughing of epidermal layers Signup and view all the answers

What is a characteristic function of IgA proteases?

Split IgA immunoglobulin Signup and view all the answers

What role does collagenase play in pathogen invasion?

It breaks down collagen Signup and view all the answers

Which organism is known to produce lecithinase, leading to gas gangrene?

Clostridium perfringens Signup and view all the answers

What is a function of the capsule produced by S. pneumoniae?

Evades phagocytosis Signup and view all the answers

What is the primary action of diphtheria toxin?

Inhibits host cell protein synthesis Signup and view all the answers

What process follows the ingestion of a microbe by a phagocyte?

Formation of a phagosome Signup and view all the answers

Study Notes

Needham's Experiment & Spontaneous Generation

Needham boiled chicken broth; microbes appeared the next day (due to lack of cover).
He hypothesized that life emerged spontaneously.
He was a British clergyman.

Spallanzani's Challenge

Spallanzani challenged Needham's theory.
He argued that microbes originated from the air.
In his experiment, he boiled broth and sealed it; no microbes appeared.

Early Challenges to Spontaneous Generation

Francesco Redi conducted experiments with meat in jars (open, gauze-covered, sealed).
Results: Maggots appeared in open and gauze-covered jars, but not the sealed jar.
He concluded maggots came from flies, not spontaneous generation.

Germ Theory of Disease: Key Figures

Oliver Wendell Holmes: Emphasized handwashing importance.
Ignaz Semmelweis: Observed higher mortality rates in maternity wards, advocated for hygiene.
John Snow: Father of epidemiology; traced cholera outbreak in London, highlighting public hygiene's role.

Tyndall's Contributions

John Tyndall discovered bacteria exist in two forms: heat-stable endospores and heat-sensitive vegetative forms.
He developed Tyndallization: intermittent heating to destroy spores.

Bacterial Genetic Transfer Mechanisms

Conjugation: Cell-to-cell transfer via sex pilus.
Transformation: Uptake of free-floating DNA by competent cells (often Gram-positive).
Competence is sometimes induced by nutrient starvation.

Bacterial Toxins

Endotoxins: Produced inside bacteria; released upon cell lysis. Examples include the toxins produced by Clostridium tetani (tetanus) and Clostridium botulinum (botulism)
Exotoxins: Secreted by bacteria. Examples include enterotoxins (affect the intestine), toxic shock syndrome toxin (TSST), exfoliative toxins (cause scalded skin syndrome), leucocidins (destroy leukocytes), and diphtheria toxin.

Virulence Factors

Capsule: Evades phagocytosis. Examples: Streptococcus pneumoniae, Klebsiella pneumoniae.
Surface antigens: Examples: V antigen (Salmonella), K antigen (E. coli).
Coagulase: Prevents phagocytosis (e.g., Staphylococcus aureus).
Fibrinolysin: Promotes spread by breaking down fibrin.
Hyaluronidase: Breaks down hyaluronic acid (tissue cement), facilitating invasion.
Hemolysins: Destroy red blood cells (alpha, beta, gamma types).
IgA proteases: Degrade IgA antibodies.
Collagenase: Breaks down collagen, enabling tissue invasion.
Lecithinase: Breaks down phospholipids (e.g., Clostridium perfringens).

Host-Defense Mechanisms Against Pathogens

Non-specific resistance: General defenses against all pathogens.
Specific immunity (adaptive): Targets specific pathogens; lasts 2-3 weeks (e.g., rabies).
Humoral immunity: Antibody-mediated; B-cells produce antibodies.
Cell-mediated immunity (CMI): T-cell mediated; targets intracellular microbes.

Immunoglobulin Classes

IgG: Most abundant; long-lived; crosses the placenta.
IgM: First antibody produced during infection; pentamer; does not cross placenta.

Microbial Control Methods

Physical (Heat): Moist heat (pasteurization, boiling, autoclaving, Tyndallization); Dry heat (hot air oven, incineration).
Radiation: Ionizing (X-ray, gamma); Non-ionizing (UV).
Chemical: Denatures proteins (alcohols, aldehydes, phenols, halogens, gases, antibiotics).
Mechanical: Filtration (air, liquid); handwashing.

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Description

This quiz covers the key experiments and figures in the history of spontaneous generation and germ theory. Explore Needham's initial hypotheses, Spallanzani's challenges, and the contributions of pioneers like Holmes and Snow to hygiene and epidemiology.