Microbiology: Pasteur, Lister, and Koch

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Questions and Answers

What practice did Sir Joseph Lister introduce to help reduce post-surgical infections?

Mandatory hand washing

Sterilization of surgical instruments using phenol (correct)

Chlorine disinfection of instruments

Pasteurization of surgical instruments

What was the main contribution of Robert Koch to microbiology?

Developing the germ theory and its postulates (correct)

Inventing pasteurization

Establishing virology through filterable agents

Introducing antiseptic surgery

What significant observation did Dmitri Ivanovski make regarding infected tobacco leaves?

They were free of any infectious agents.

They could not be extracted for further study.

They required chlorination to eliminate toxins.

They remained infectious despite rigorous filtration. (correct)

Which of the following describes one of Koch's Postulates?

The cultured microorganism must cause disease in a healthy host. Signup and view all the answers

What method did Louis Pasteur use to prevent spoilage in liquids such as alcohol and milk?

Heating to kill pathogenic microbes Signup and view all the answers

What is the primary basis for identification in Bergey's Manual of Determinative Bacteriology?

Differential staining and biochemical tests Signup and view all the answers

Which bacterial classification resource is based on rRNA sequencing?

Bergey's Manual of Systematic Bacteriology Signup and view all the answers

What was the earlier known name of phenol that Sir Joseph Lister used?

Carbolic acid Signup and view all the answers

What aspect does the first postulate of Koch's Postulates emphasize?

Microorganisms must be found in abundance in diseased organisms. Signup and view all the answers

What distinguishes bacteria from other organisms in terms of cell structure?

Single-celled and lack a nucleus Signup and view all the answers

Which resource provides information on classifying fungi?

Mycobank Signup and view all the answers

Which of the following practices was not a contribution of Louis Pasteur?

Invention of antiseptic surgery Signup and view all the answers

What is the primary purpose of the Approved Lists of Bacterial Names?

To list species of known prokaryotes based on studies Signup and view all the answers

Which statement about viruses is accurate?

Viruses require living cells to replicate. Signup and view all the answers

What is the term used for the inert form of a virus outside of a host cell?

Virion Signup and view all the answers

What defines a naked virus?

Virus lacking a lipid coat. Signup and view all the answers

Which hypothesis regarding the origin of viruses suggests they may evolve from larger nucleic acids?

The fugitive nucleic acid hypothesis Signup and view all the answers

What factor is NOT relevant for the classification of viruses?

Presence of a nuclear membrane Signup and view all the answers

What is the structural unit that forms the protein coat of a virus called?

Capsomer Signup and view all the answers

Which of the following accurately describes RNA viruses?

They can exist as both single-stranded and double-stranded. Signup and view all the answers

How is the complex of viral nucleic acid and protein referred to?

Nucleocapsid Signup and view all the answers

What term refers to the shape of bacterial cells?

Morphology Signup and view all the answers

Which of the following is NOT a type of bacterial shape?

Chromosome Signup and view all the answers

What is the main component of the bacterial cell wall?

Peptidoglycan Signup and view all the answers

What structure is primarily involved in bacterial motility?

Flagella Signup and view all the answers

Which bacterial structure helps in attachment to host cells and evasion of the immune system?

Pili Signup and view all the answers

How large can bacteria vary in size?

0.1 to 50 micrometres Signup and view all the answers

What type of bacteria has a round shape?

Coccus Signup and view all the answers

Which of the following is a characteristic of flagella in bacteria?

Made of flagellin protein Signup and view all the answers

What are the two main components of bacterial metabolism?

Anabolism and Catabolism Signup and view all the answers

What is the primary role of facilitated diffusion in bacteria?

To transport nutrients into the cytoplasm Signup and view all the answers

Which of the following is associated with catabolism?

Breaking down complex molecules Signup and view all the answers

What type of bacteria are classified as chemoorganotrophs?

Pathogenic bacteria that oxidize preformed organic molecules Signup and view all the answers

Which biochemical mechanism is NOT utilized in bacterial metabolism?

Photosynthesis Signup and view all the answers

Study Notes

Louis Pasteur (1864)

Invented Pasteurization
He discovered that heating beer, alcohol, and milk to a specific temperature for a specific time kills pathogenic microbes without changing the taste.

Sir Joseph Lister (1867)

Introduced the use of phenol (carbolic acid) to sterilize surgical instruments, clean wounds, and reduce post-surgical infections.
Lister's work was inspired by Pasteur's discoveries about microbes.

Robert Koch (1876)

Provided the first proof of the Germ Theory by studying Bacillus anthracis.
Developed Koch's Postulates, which helped prove that microbes are the causative agents of infections and diseases.

Koch’s Postulates

Postulate 1: The microorganism must be found in abundance in diseased organisms but not in healthy organisms.
Postulate 2: The microorganism must be isolated from a diseased organism and grown in pure culture.
Postulate 3: The cultured microorganism should cause disease when introduced into a healthy organism.
Postulate 4: The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original causative agent.

Dmitri Ivanovski (1892)

Discovered the basis for the field of Virology.
Found that extracts from infected tobacco leaves remained infectious even after rigorous filtration.
This suggested that the infectious agent was smaller than bacteria, leading to the discovery of viruses.

Viruses

Genetic elements that can replicate independently of a cell’s chromosomes but not independently of cells themselves.
Submicroscopic entities consisting of a single nucleic acid (DNA or RNA) surrounded by a protein coat.
Viruses are obligate intracellular parasites, meaning they can only replicate inside living cells.
Virions are the extracellular state of a virus, where the virus particle is metabolically inert.

Origin of Viruses

Two hypotheses:
- Viruses could be fugitive pieces of nucleic acid from larger organisms that became active.
- Viruses once lived outside host cells but lost the genes required for independent survival due to a parasitic lifestyle.

Virion Structure

DNA or RNA viruses, but not both.
Enveloped viruses (protein and lipid coat) vs. naked viruses (only a protein coat).
The nucleic acid is always located within the particle, surrounded by a protein coat called the capsid.
The capsid is formed of structural subunits called capsomers.
The nucleocapsid is the complete complex of nucleic acid and protein.

Virus Classification

Depends on:
- Species they infect: animal, plant, bacteria.
- Presence or absence of a lipid envelope.
- Symmetry of the nucleocapsid.
- Type of nucleic acid (DNA or RNA).
- Number of nucleic acid strands, their structure, and the polarity of the viral genome.

Bacterial Classification

Bacteria are single-celled microbes with a simpler cell structure than other organisms.
Classified based on:
- Morphology (shape)
- Structure
- Metabolism

Bacterial Morphology

Coccus: Round shape.
- Examples: Streptococcus, Neisseria, Staphylococcus.
Bacilli: Elongated, rod-shape.
- Examples: Escherichia coli, Bacillus anthracis.
Other shapes:
- Vibrio: Comma-shaped.
- Spirillum: Spiral-shaped.
- Spirochetes: Flexible, spiral-shaped.
- Example: Treponema pallidum (causes syphilis).

Bacterial Structure

Intracellular structures:
- Bacterial chromosome: Contains the genetic material.
- Plasmids: Extrachromosomal DNA molecules (not always present).
- Ribosomes: Involved in protein synthesis (70S, consisting of 30S and 50S subunits).
- Cell membrane: Regulates the passage of molecules into and out of the cell (no cholesterol).
Extracellular structures:
- Flagella: Long, helical filaments involved in movement (chemotaxis).
- Pili (Fimbriae): Short, rigid structures involved in attachment to other bacteria or host cells.
- Cell wall: Provides structural support and protects the bacteria.
- Capsule: A protective layer outside the cell wall (not always present).

Flagella

Long, helical filaments that extend from the cell surface. Made primarily of the protein flagellin.
Involved in chemotaxis, the movement of bacteria in response to chemical signals.

Pili (Fimbriae)

Short, rigid, and numerous.
Involved in:
- Attachment to other bacteria and/or host cells.
- Avoiding phagocytosis (engulfment by immune cells).
- Avoiding immune recognition.

Cell Wall

Provides structural support and protects the cell.
The main component is peptidoglycan (murein).
The cell wall allows the passage of small molecules: amino acids, oligosaccharides, and small peptides.
The cell membrane transports nutrients into the cytoplasm via facilitated diffusion or active transport.
The cell wall also allows some larger molecules to be taken up after preliminary digestion in the periplasmic space (in Gram-negative bacteria).

Microbial Metabolism

Metabolism: The sum of biochemical reactions required for energy generation and the synthesis of cell material from small molecules.
Understanding bacterial metabolism is important for controlling bacterial growth.

Components of Metabolism

Anabolism (biosynthesis): Building complex molecules from simple ones, requiring energy (ATP).
Catabolism (degradation): Breaking down complex molecules into simple ones, generating energy (ATP).
Biochemical mechanisms:
- Aerobic respiration
- Anaerobic respiration
- Fermentation

Metabolic Diversity

Bacteria are classified based on:
- Source of energy: Chemotrophs obtain energy from chemical compounds, phototrophs obtain energy from light.
- Source of carbon: Autotrophs use carbon dioxide as their carbon source, heterotrophs use preformed organic compounds as their carbon source.
- Source of electron acceptors (energy production): Organotrophs use organic molecules, lithotrophs use inorganic molecules.

Importance of Organotrophs

All pathogenic bacteria are organotrophs, meaning they obtain energy by oxidizing preformed organic molecules from their environment.

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Description

Dive into the groundbreaking contributions of Louis Pasteur, Sir Joseph Lister, and Robert Koch in the field of microbiology. This quiz covers their key discoveries, inventions, and the development of Koch's Postulates, which paved the way for modern microbiology and infection control.