Viruses vs. Bacteria: Structure, Life Cycles, and Pathogenesis

Compare the structures and life cycles of viruses versus bacteria

Viruses are acellular entities that require a host cell to replicate, consisting of genetic material (DNA or RNA) surrounded by a protein coat. Bacteria are unicellular organisms with a complex structure, including a cell wall, cell membrane, and metabolic machinery that allows them to reproduce independently. Life cycles of viruses include lytic (destructive) and lysogenic (integrative) phases, while bacteria reproduce asexually through binary fission.

Explain the function and chemical composition of viral capsids, envelopes, and spikes

Viral capsids are protein shells that protect viral genetic material and aid in host cell recognition and attachment. Envelopes are lipid membranes derived from host cells that surround some viruses, enhancing their ability to infect. Spikes are glycoprotein structures on the viral surface that facilitate attachment to host cells and are crucial for viral entry.

Define a viral species, host range, and tissue tropism

A viral species is a group of viruses sharing common characteristics and genetic material. Host range refers to the variety of host organisms a virus can infect, while tissue tropism is the specific tissues or cell types within a host that a virus can infect.

Compare and contrast the mechanisms of lytic versus lysogenic cycles of bacteriophage replication

In the lytic cycle, a bacteriophage infects a host cell, replicates rapidly, and causes cell lysis, releasing new virions. In the lysogenic cycle, the viral DNA integrates into the host genome and replicates along with it without causing immediate harm, potentially leading to lytic cycles later.

Summarize the mechanism and effects of lysogenic conversion

Lysogenic conversion occurs when a bacteriophage integrates its DNA into the bacterial genome, potentially altering the host's phenotype, such as introducing new traits like toxin production or antibiotic resistance.

Explain why and how bacteriophages can be used to fight bacterial infections

Bacteriophages can specifically target and kill bacteria, making them potential alternatives to antibiotics. They can be used in phage therapy to treat bacterial infections, particularly those resistant to conventional antibiotics.

Explain the purpose of a plaque assay and outline its basic steps

A plaque assay is used to quantify viral particles in a sample. Basic steps include diluting the viral sample, mixing it with host cells, allowing infection, and then overlaying with agar to visualize plaques formed by lysed cells.

Outline the steps by which an animal virus can enter a host cell and produce new virions

Animal viruses can enter host cells via direct fusion with the cell membrane or endocytosis. Once inside, they uncoat, replicate their genome, translate proteins, assemble new virions, and release them through budding or cell lysis.

Compare the replication of bacteriophages versus animal viruses

Bacteriophages typically inject their DNA into host bacteria and replicate within the bacterial cell, while animal viruses often enter the host cell via fusion or endocytosis, replicating in the cytoplasm or nucleus.

Compare and contrast entry by fusion versus endocytosis

Fusion involves the viral envelope merging with the host cell membrane, allowing direct entry of the viral genome. Endocytosis involves the host cell engulfing the virus in a vesicle, which then releases the viral contents inside the cell.

Describe the steps by which herpes virus replicates

Herpes virus enters the host cell, uncoats, and replicates its DNA in the nucleus. It then synthesizes viral proteins, assembles new virions, and exits the cell via exocytosis, often causing cell damage.

Define a latent viral infection and explain why/when reactivation can occur

A latent viral infection occurs when a virus remains dormant in the host without causing symptoms. Reactivation can occur due to stress, immunosuppression, or other triggers, leading to the re-emergence of symptoms.

Compare and contrast the transmission and signs/symptoms of HSV-1 versus HSV-2

HSV-1 primarily causes oral herpes, often transmitted through oral contact, while HSV-2 primarily causes genital herpes, transmitted through sexual contact. Both can cause painful sores, but their primary sites of infection differ.

Outline the steps by which HPV infections can lead to cancer

HPV infects epithelial cells, where it can integrate into the host genome, leading to uncontrolled cell division and potential malignancy. Certain high-risk strains are associated with cervical and other cancers.

Describe the cytopathic effect of viruses

Cytopathic effects are observable changes in host cells due to viral infection, including cell lysis, syncytia formation, and altered cell metabolism, which can be used for viral identification in the lab.

Summarize how the poliovirus is replicated and can spread throughout the body

Poliovirus enters the body through the oral route, replicates in the gastrointestinal tract, and spreads to the nervous system, affecting motor neurons. Its RNA genome allows rapid replication and spread.

Explain how the polio virus leads to the signs and symptoms of disease

Poliovirus primarily affects motor neurons in the spinal cord, leading to muscle weakness, paralysis, and potentially respiratory failure, with symptoms appearing after an incubation period.

Compare and contrast the two available polio vaccines

The inactivated polio vaccine (IPV) is injected and provides immunity without risk of disease, while the oral polio vaccine (OPV) is easier to administer but can lead to vaccine-derived polio in rare cases.

Describe the origin and consequences of vaccine-derived polio

Vaccine-derived polio occurs when the live attenuated virus in OPV mutates and causes disease. It poses a risk in populations with low vaccination coverage.

Explain how rhinoviruses cause cold symptoms

Rhinoviruses infect the upper respiratory tract, leading to inflammation, increased mucus production, and symptoms such as coughing, sneezing, and sore throat.

Describe the challenges of treating colds

There is no cure for the common cold; treatment focuses on symptom relief. Prevention includes good hygiene practices like handwashing and avoiding close contact with infected individuals.

Compare and contrast influenza and the common cold

Influenza is caused by influenza viruses and presents with more severe symptoms, including high fever and body aches, while the common cold is usually milder. Treatments for influenza may include antiviral medications.

Identify the function of the influenza HA versus NA spikes

Hemagglutinin (HA) spikes facilitate viral entry by binding to host cell receptors, while neuraminidase (NA) spikes help release new virions from infected cells.

Explain how and where the influenza virus replicates in a human host

Influenza virus replicates in the epithelial cells of the respiratory tract, utilizing host cell machinery and molecules for transcription and translation of viral proteins.

Compare and contrast antigenic drift and antigenic shift

Antigenic drift involves small mutations in viral genes leading to gradual changes in surface proteins, while antigenic shift is a major change due to reassortment of viral genomes, often resulting in new subtypes.

Explain the origin of the H1N1 1918 and 2009 pandemics

The H1N1 1918 pandemic originated from a novel influenza strain, while the 2009 pandemic arose from a reassorted virus containing genes from swine, avian, and human influenza viruses.

Explain how flu vaccines are developed

Flu vaccines are developed by predicting circulating strains, growing them in eggs or cell cultures, and then inactivating or attenuating the virus for use in vaccines, with benefits including reduced disease severity.

Explain the origin of the HIV-1 and HIV-2 viruses

HIV-1 originated from simian immunodeficiency virus (SIV) in chimpanzees, while HIV-2 is derived from SIV in sooty mangabey monkeys, both crossing into humans.

Outline the steps of HIV pathogenesis

HIV enters the body, binds to CD4 and CCR5 receptors, reverse transcribes its RNA into DNA, integrates into the host genome, and replicates, leading to CD4 cell depletion and progression to AIDS.

Describe the disease progression from initial infection to AIDS

Initial HIV infection may be asymptomatic or cause flu-like symptoms. Over time, CD4 counts decline, leading to opportunistic infections and eventual progression to AIDS.

Explain the mechanism of genetic resistance to HIV infection

Genetic resistance to HIV is often due to mutations in the CCR5 gene, which encodes a receptor used by HIV to enter cells. Individuals with two copies of the mutation are highly resistant.

Explain how HIV infections are diagnosed

HIV infections are diagnosed using antibody tests or nucleic acid tests, with seroconversion indicating the development of detectable antibodies following infection.

Explain how HIV is treated

HIV is treated with antiretroviral therapies targeting various stages of the viral life cycle, including reverse transcriptase inhibitors and protease inhibitors. Pre-exposure prophylaxis (PrEP) is recommended for high-risk individuals.

Illustrate the structure of the SARS-CoV-2 virus

SARS-CoV-2 has a spherical shape with spike proteins protruding from its surface, an envelope, and a single-stranded RNA genome, which is crucial for its replication and evolution.

Compare and contrast the three coronaviruses causing severe human diseases

SARS-CoV, MERS-CoV, and SARS-CoV-2 differ in mortality rates, transmissibility, and host species, with SARS-CoV-2 being more transmissible but less lethal than SARS-CoV.

Outline the steps of SARS-CoV-2 replication in a cell

SARS-CoV-2 binds to ACE2 receptors, enters the host cell, releases its RNA, replicates, assembles new virions, and exits the cell to infect others.

Identify the tissues impacted by SARS-CoV-2

SARS-CoV-2 primarily affects the respiratory tract but can also impact other tissues, including the cardiovascular and gastrointestinal systems, leading to a range of symptoms.

Compare and contrast the vaccine technologies used by Pfizer/Moderna vs Novavax

Pfizer and Moderna use mRNA technology to instruct cells to produce viral proteins, while Novavax uses a protein subunit approach to elicit an immune response.

Explain the pros and cons of the methods by which we can diagnose and treat patients with COVID

Diagnosis methods include PCR and rapid antigen tests, each with benefits and limitations in sensitivity and specificity. Treatment options range from supportive care to antiviral medications, with varying effectiveness.

Identify the basic shapes, aggregations, and Gram reaction of bacteria

Bacteria can be classified by shape (cocci, bacilli, spirilla), aggregation (singular, chains, clusters), and Gram reaction (Gram-positive or Gram-negative based on cell wall composition).

Identify what type of microscope was used to view a microbe

The type of microscope used can vary; light microscopes are common for viewing larger microbes, while electron microscopes are used for detailed visualization of smaller structures.

Define germ theory and summarize the experiments that evaluated biogenesis vs spontaneous generation

Germ theory posits that microorganisms cause disease, supported by experiments like Pasteur's swan-neck flask experiment, which disproved spontaneous generation by showing that sterilized broth remained clear when protected from contamination.

Understand each step and the terminology of the Gram-stain

The Gram-stain process involves crystal violet staining, iodine treatment, decolorization with alcohol, and counterstaining with safranin, distinguishing bacteria as Gram-positive (purple) or Gram-negative (pink).

Describe the function and structure of peptidoglycan

Peptidoglycan is a polymer that forms a rigid structure in bacterial cell walls, providing shape and protection against osmotic pressure, composed of sugars and amino acids.

Compare and contrast the cell envelopes of Gram-positive vs Gram-negative bacteria

Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, while Gram-negative bacteria have a thin peptidoglycan layer surrounded by an outer membrane, which contains lipopolysaccharides.

Describe the function and structure of flagella

Flagella are long, whip-like structures that provide motility to bacteria, composed of the protein flagellin, and rotate to propel the cell through liquid environments.

Solve osmosis problems: identify hypertonic vs hypotonic solutions

Hypertonic solutions have a higher solute concentration than the cell, causing water to flow out, while hypotonic solutions have a lower solute concentration, causing water to flow into the cell.

Compare the function of NADH versus ATP in metabolism

NADH is an electron carrier that stores energy from metabolic reactions, while ATP is the primary energy currency of the cell, providing energy for various cellular processes.

Explain the relationships between glycolysis, the Krebs cycle, and respiration

Glycolysis breaks down glucose into pyruvate, which enters the Krebs cycle for further oxidation, producing electron carriers that feed into the electron transport chain for ATP production.

Compare the growth conditions of obligate vs facultative halophiles

Obligate halophiles require high salt concentrations for growth, while facultative halophiles can grow in varying salt concentrations but prefer lower levels.

Identify whether different chemicals are used for sterilization or disinfection

Sterilization methods eliminate all forms of microbial life, while disinfection reduces pathogens to safe levels. Chemicals like bleach are disinfectants, while autoclaving is a sterilization method.

Summarize the purpose and basic steps of transcription

Transcription is the process of synthesizing RNA from a DNA template, involving initiation, elongation, and termination, resulting in mRNA that carries genetic information for protein synthesis.

Use the genetic code to determine protein sequences

The genetic code consists of codons, three-nucleotide sequences that correspond to specific amino acids, allowing for the translation of mRNA into protein sequences.

Describe the structure of DNA and how this structure enables accurate copying

DNA is a double helix composed of nucleotides, with complementary base pairing (A-T, C-G) ensuring accurate replication during cell division.

Compare and contrast conjugation, transformation, and transduction

Conjugation involves direct transfer of DNA between bacteria, transformation is the uptake of free DNA from the environment, and transduction is the transfer of DNA via bacteriophages.

Compare and contrast endotoxins vs. exotoxins

Endotoxins are components of the bacterial cell wall (lipopolysaccharides) that can trigger strong immune responses, while exotoxins are proteins secreted by bacteria that can cause damage to host cells.

Identify examples of contact transmission

Contact transmission includes direct (person-to-person), indirect (via contaminated surfaces), and droplet transmission (via respiratory droplets).

Define and recognize examples of incidence rates, prevalence, and basic reproduction numbers

Incidence rates measure new cases in a population over time, prevalence measures total cases at a specific time, and the basic reproduction number (R0) indicates how many people one infected person will infect on average.

Identify the route of transmission, major signs/symptoms, and treatment strategy for major pathogens

For each major pathogen, identify how it spreads (e.g., respiratory, vector-borne), common symptoms (e.g., fever, cough), and treatment approaches (e.g., antibiotics for bacterial infections, antivirals for viral infections).

Compare and contrast infections to intoxications

Infections result from the growth of pathogens in the body, while intoxications occur from the ingestion of toxins produced by pathogens. Symptoms and treatment strategies differ based on the underlying cause.

Compare and contrast the major cellular structures of bacteria, protozoa, fungi, helminths, and viruses

Bacteria are prokaryotic cells with cell walls, protozoa are unicellular eukaryotes, fungi have cell walls made of chitin, helminths are multicellular parasites, and viruses are acellular entities.

Perform serial dilution calculations

Serial dilutions involve systematically reducing the concentration of a substance in solution, often used to determine the concentration of microorganisms in a sample.

Interpret the results of diagnostic assays

Diagnostic assays such as hemolysis tests, fermentation assays, and disk diffusion assays provide information about microbial characteristics and susceptibility to antibiotics.

Identify if media is selective, differential, neither, or both

Selective media inhibit the growth of certain organisms while allowing others to grow, differential media allow for the differentiation of organisms based on biochemical characteristics, and some media can be both.