Introduction to Microbiology: Bacteria and Viruses

Flashcards covering historical impacts of infectious diseases, bacterial and viral structures, toxin mechanisms, viral replication steps, and virus-host cell interactions.

What epidemic prevented Louis 16th's invasion of England in 1779 and how many French troops were claimed by it?

A smallpox epidemic erupted and claimed ~$8{,}000$ of the French troops.

What disease did Napoleon's troops contract in Haiti in 1802, and what historical outcome did it help lead to in 1804?

They contracted yellow fever and died, which resulted in Haiti's independence in 1804, ending French rule and abolishing slavery in the colony.

What land purchase is suggested to have been sold to the United States by Napoleon due to fear of infectious disease epidemics in the New World?

The Louisiana Purchase.

How was biological warfare practiced during the 14th Century siege warfare?

Victims of The Plague (Black Death) were catapulted over the walls of cities under siege to weaken and kill those within.

What action was taken by British General Amherst during the French & Indian War (1754–1763)?

General Amherst ordered British troops to supply Indians with blankets infected with smallpox.

What percentage of Europe's population was killed by the Black Death between 1346 and 1353?

~$50\%$ of the population.

How did the Great Fire of London in 1666 affect the spread of the Black Death?

Post-fire construction used wood and stone instead of thatched roofs, eliminating a major reservoir for rats carrying fleas infected with the plague bacterium.

What unexpected health consequence resulted from introducing the closed sewer system in England in the 1840s?

It eliminated natural exposure to poliovirus at an early age (natural immunity), leading to an epidemic of paralytic poliomyelitis in the 1950s.

What primary target or focus in the human body do infectious microorganisms target?

The living cell of your body.

What are the six key characteristics of a living cell listed in the lecture?

1. Genome composed of DNA
2. Surrounded by plasma membrane
3. Capable of independent growth
4. Capable of independent protein synthesis
5. Capable of independent metabolism
6. Replicates by division (fission)

What eight categories of infectious organisms are identified in the notes?

Bacteria, Viruses, Mycoplasma, Fungi, Rickettsia, Protozoa, Chlamydia, and Parasitic worms.

What are the key structural components of a prokaryotic cell as depicted in this diagram?

Capsule, Cell Wall, Cytoplasmic Membrane, Ribosomes, Pili, Cytoplasm, Nucleoid, and Flagella.

Which bacterial shape/morphology is shown in this micrograph?

Cocci.

Which bacterial shape/morphology is depicted in this micrograph?

Bacilli.

Which bacterial morphology is shown in this light micrograph?

Spirochetes.

What is endotoxin and what is its primary structural component in Gram-negative bacteria?

Endotoxin is a structural component of the bacterium made of lipopolysaccharide, a major component of the outer cell wall in Gram-negative bacteria.

What are four specific functions or types of bacterial exotoxins described in the lecture?

1. Proteases that cleave proteins linking one cell to another
2. Toxins that alter intracellular signaling/regulatory pathways
3. Neurotoxins that disrupt release of neurotransmitters (paralysis)
4. Superantigens that cause massive T-cell proliferation/cytokine release

What five infectious diseases caused by bacteria are explicitly listed in the lecture?

Gonorrhea, Plague (Black Death), Syphilis, Leprosy, and Tuberculosis.

How do viruses compare in size to the smallest bacteria according to principles of virology?

Viruses are about $2$ orders of magnitude smaller than the smallest bacterium.

How is a virion defined in structural virology?

An infectious virus particle.

What is the structural definition of a capsomere?

A morphological subunit of a capsid.

What geometric shape with 20 triangular facets builds many small virus capsids?

An icosahedron.

What numerical symmetry ratio is formed by capsomeres in icosahedral viral capsids?

$5 : 3 : 2$ symmetry.

How are capsomeres and RNA organized in helical viral capsid symmetry?

Capsomeres are arranged as a spiral staircase or helix, and RNA forms a spiral within the nucleocapsid.

How do enveloped viruses acquire their envelope, and where do the lipids and proteins originate?

They acquire it from the host cell during maturation via 'budding'. Lipids are derived directly from the host cell membrane, while envelope proteins (glycoproteins) are virus-encoded.

What is the tegument of a virus and what are its functional roles?

The area between the envelope and nucleocapsid composed of virus-encoded proteins. It functions as antigens to stimulate an immune response and alters host cell functions at the time of infection.

Why are enveloped viruses generally less stable than nonenveloped viruses?

An enveloped virus loses its infectivity if its envelope is removed or disrupted, reflecting different mechanisms used to gain entrance into host cells.

What are the characteristic features of a complex virus structure as seen in Poxviruses?

Brick-shaped virions with an external coat of lipid and tubular/globular protein enclosing lateral bodies and an internal core containing the genome. They replicate in cytoplasmic factories visible by light microscopy.

What is the fundamental difference in replication method between host cells/bacteria and viruses?

Cells of the body and bacteria replicate by fission, whereas viruses replicate by assembly.

What are the 10 basic steps in virus replication in sequential order?

1. Attachment
2. Adsorption (penetration)
3. Uncoating
4. Transcription of early mRNAs
5. Translation of early proteins (enzymes)
6. Replication of parental virus genome
7. Transcription of late mRNAs
8. Translation of late proteins (structural proteins)
9. Assembly
10. Release

What defines a productive virus-host cell interaction?

High production of new infectious progeny virus where the host cell is eventually killed within hours to days.

What defines a chronic persistent viral infection?

Low level production of new infectious progeny virus where the host cell survives for a long period, with its functions either unaffected or partially impaired.

What occurs during an abortive viral infection?

Viral replication is blocked at any step after attachment/adsorption because the host cell cannot supply a viral requirement, terminating productive infection.

What characterises a latent viral infection?

The virus becomes quiescent, conserving the complete viral genome with little transcription or translation, until future events trigger reactivation of productive replication.

What is viral transformation in the context of host cell interaction?

An interaction causing a heritable change in host cell phenotype (without killing it), leading to more vigorous growth, immortalization in vitro, and malignancy in vivo.