Lecture Final (past material )

Who was Antonie van Leeuwenhoek and what did he contribute to microbiology?

Antonie van Leeuwenhoek was the first scientist to observe and describe living microorganisms ("animalcules") using his handcrafted microscopes. He is known as the Father of Microbiology.

Who was Robert Hooke and what was his contribution?

Robert Hooke improved the microscope and observed cork cells, introducing the term "cell." He published Micrographia, one of the first books describing microscopic observations.

What did Francesco Redi prove?

Francesco Redi disproved spontaneous generation for larger organisms by showing that maggots come from flies, not rotting meat.

What was John Needham's experiment?

John Needham boiled broth but did not sterilize it completely. Microbes still grew, leading him to incorrectly support spontaneous generation

What did Lazzaro Spallanzani discover?

Spallanzani boiled broth longer and sealed the flasks, preventing microbial growth. He argued that microorganisms come from other microorganisms.

How did Louis Pasteur disprove spontaneous generation?

Pasteur used swan-neck flasks, allowing air in but trapping microorganisms in the curved neck. Sterile broth remained free of microbial growth unless contaminated.

What is the Germ Theory of Disease?

The Germ Theory states that microorganisms cause infectious diseases.

Who developed the Germ Theory of Disease?

Louis Pasteur proposed the Germ Theory, and Robert Koch provided experimental proof.

What were Robert Koch's contributions?

Robert Koch:

• Proved bacteria cause disease.

• Identified the bacteria causing anthrax, tuberculosis, and cholera.

• Developed Koch's Postulates.

What are Koch's Postulates?

Four steps used to prove that a specific microorganism causes a disease:

1. Present in every diseased individual.

2. Isolated and grown in pure culture.

3. Causes disease in a healthy host.

4. Re-isolated from the newly infected host.

Who discovered penicillin?

Alexander Fleming discovered penicillin in 1928 after observing that a mold inhibited bacterial growth

Who developed penicillin into a usable antibiotic?

Howard Florey and Ernst Chain purified and mass-produced penicillin.

Who discovered the first synthetic antibiotic?

Paul Ehrlich developed Salvarsan, the first antimicrobial drug used to treat syphilis.

Why do microbiologists use microscopes

Most microorganisms are too small to be seen with the naked eye. Microscopes allow scientists to observe cell shape, size, arrangement, and internal structures.

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What are the advantages of using a microscope?

Microscopes help identify microorganisms, diagnose infections, study cell structures, and observe bacterial behavior.

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Why do we stain bacteria?

Bacteria are nearly transparent. Staining increases contrast, allowing their shape, arrangement, and structures to be seen clearly.

What are the benefits of bacterial staining?

Staining helps identify bacteria, differentiate species, diagnose infections, and visualize special structures such as capsules and endospores.

Why is the Gram stain important?

It is the most common differential stain used to classify bacteria into Gram-positive and Gram-negative groups, helping identify pathogens and guide antibiotic treatment.

Why is the Gram stain called a differential stain?

Because it separates bacteria into two groups based on differences in cell wall structure.

What color are Gram-positive bacteria?

Purple.

What color are Gram-negative bacteria?

Pink or red.

Why do Gram-positive bacteria stain purple?

Their thick peptidoglycan layer traps the crystal violet-iodine complex during decolorization.

Why do Gram-negative bacteria stain pink?

Alcohol removes the outer membrane and crystal violet, allowing the cells to absorb the safranin counterstain.

What are the four steps of the Gram stain?

• Crystal violet

• Iodine

• Alcohol (decolorizer)

• Safranin

What is the function of the capsule?

Protects against phagocytosis, prevents dehydration, and helps bacteria adhere to surfaces.

What is the glycocalyx?

A sticky outer covering that helps bacteria attach to surfaces and form biofilms

What is the function of the cell wall?

Provides shape, support, and protection against osmotic pressure.

What is peptidoglycan?

A strong mesh-like polymer that gives bacterial cell walls rigidity

What is the plasma membrane?

Controls movement of substances into and out of the cell and is the site of ATP production

What are ribosomes?

Structures that synthesize proteins

What is the nucleoid?

The region containing the bacterial chromosome.

What are plasmids?

Small circular DNA molecules carrying extra genes such as antibiotic resistance.

What are pili?

Hair-like structures used for attachment and DNA transfer during conjugation.

What are fimbriae?

Short protein fibers that help bacteria attach to host tissues.

What are flagella?

Long whip-like structures used for movement.

What are endospores?

Dormant, highly resistant survival structures produced by certain bacteria.

What are bacteria?

Single-celled prokaryotes with peptidoglycan cell walls.

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What are archaea?

Prokaryotes lacking peptidoglycan that often live in extreme environments.

What are fungi?

Eukaryotic organisms including yeasts and molds that absorb nutrients.

What are protozoa?

Single-celled eukaryotes that usually move using cilia, flagella, or pseudopods.

What are algae?

Photosynthetic eukaryotes that produce oxygen.

What are viruses?

Acellular infectious particles that require a host cell to reproduce.

What are helminths?

Parasitic worms.

How do bacteria reproduce?

By binary fission.

What are the steps of binary fission?

1. DNA replication

2. Cell elongation

3. Chromosomes separate

4. Septum forms

5. Cell divides into two identical daughter cells

What is PCR?

Polymerase Chain Reaction amplifies millions of copies of a DNA segment.

What enzyme is used in PCR?

Taq polymerase.

What are the three PCR steps?

1. Denaturation

2. Annealing

3. Extension

What is DNA cloning?

: Making identical copies of DNA by inserting it into a plasmid vector.

What are restriction enzymes?

Enzymes that cut DNA at specific sequences.

What is DNA ligase?

An enzyme that joins DNA fragments together

What is gel electrophoresis?

A technique that separates DNA fragments by size.

What is DNA fingerprinting

A method of identifying individuals based on unique DNA patterns.

What is CRISPR-Cas9?

A gene-editing system that cuts DNA at specific locations.

What is direct contact transmission?

Disease spread through physical contact between infected and susceptible individuals.

What is indirect contact transmission?

Disease spread through contaminated objects called fomites.

What is droplet transmission?

Spread by large respiratory droplets during coughing, sneezing, or talking

What is vehicle transmission?

Spread through contaminated food, water, blood, or air.

What is vector transmission?

Spread by living organisms such as mosquitoes, ticks, or fleas.

What are portals of entry?

Routes microorganisms use to enter the body.

What are common portals of entry?

Respiratory tract, gastrointestinal tract, urogenital tract, skin, mucous membranes, and placenta

What are portals of exit?

Routes microorganisms leave an infected host.

What are common portals of exit?

Respiratory secretions, blood, feces, urine, saliva, skin, and reproductive fluids

Why are portals of entry and exit important?

They allow pathogens to spread from one host to another, continuing the chain of infection.

What is the first line of defense?

Physical and chemical barriers that prevent pathogen entry.

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Give examples of the first line of defense.

Skin, mucous membranes, mucus, tears, saliva, stomach acid, normal microbiota, and cilia.

What is the second line of defense?

Innate immune responses that act after pathogens enter the body.

Components of the second line of defense?

Phagocytes, inflammation, fever, complement proteins, interferons, natural killer cells, and antimicrobial proteins.

What is inflammation?

A protective response causing redness, heat, swelling, pain, and increased blood flow.

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What is the third line of defense?

Adaptive immunity involving B cells, T cells, antibodies, and memory

Why is the third line of defense important?

It provides specific immunity and long-term protection through immunological memory.

What are antibiotics?

Drugs that kill bacteria or stop bacterial growth.

How do antibiotics work?

They target bacterial structures such as:

• Cell wall

• Protein synthesis

• DNA replication

• RNA synthesis

• Metabolic pathways

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Why don't antibiotics work against viruses?

Viruses lack the cellular structures that antibiotics target and reproduce inside host cells.

What is antibiotic resistance?

The ability of bacteria to survive antibiotic treatment

How do bacteria become resistant through mutations?

Random DNA mutations can create traits that allow bacteria to survive antibiotics.

How do bacteria gain resistance genes?

Through horizontal gene transfer:

• Conjugation

• Transformation

• Transduction

What is conjugation?

Transfer of plasmids through a pilus from one bacterium to another.

What is transformation?

Uptake of free DNA from the environment.

How have humans contributed to antibiotic resistance?

• Overprescribing antibiotics

• Not finishing prescriptions

• Using antibiotics for viral infections

• Overuse in livestock

• Self-medicating

• Poor infection control

Why is antibiotic resistance a major concern?

t makes infections harder to treat, increases healthcare costs, leads to longer hospital stays, and can result in more deaths.

What can be done to slow antibiotic resistance?

• Use antibiotics only when necessary.

• Finish the entire prescription.

• Never share antibiotics.

• Practice good hand hygiene.

• Get vaccinated.

• Improve infection control in healthcare settings.

• Support antibiotic stewardship programs.