Quiz 5 Flashcards
What is a pathogen?
An organism, cell, virus, or prion that causes disease.
Define microbiota.
The collective of microorganisms that reside in or on an organism.
How many microbial cells are estimated to be inside a human?
10^14 cells.
What is the microbiome?
The combined genomes of the various species of a defined microbiota.
What are the three types of microbe-host interactions?
- Mutualism
- Commensalism
- Parasitism
What are primary pathogens?
Pathogens that cause overt disease in healthy people.
What are opportunistic pathogens?
Normal microbes of the flora that can cause disease in individuals with weakened immune systems or if they gain access to normally sterile parts of the body.
Define facultative pathogens.
Bacteria that replicate in an environmental reservoir and only cause disease if they encounter a host.
What are obligate pathogens?
Bacteria that can only replicate inside their host.
List the successful pathogen entry requirements.
- Enter the host
- Find a nutritionally compatible niche
- Avoid/subvert/circumvent the host’s immune responses
- Replicate
- Exit one host and spread to another
What are the shapes of bacteria?
- Spiral
- Sphere
- Rod
What distinguishes Gram-positive bacteria from Gram-negative bacteria?
Gram-positive have a thick peptidoglycan cell wall; Gram-negative have a thinner cell wall and an outer membrane containing LPS.
What are virulence genes?
Genes that contribute to an organism’s ability to cause disease.
What are virulence factors?
Proteins encoded by virulence genes.
What are pathogenicity islands?
Large clusters of virulence genes on a chromosome.
What are the three mechanisms of horizontal gene transfer?
- Transformation
- Transduction
- Conjugation
What are the two subunits of bacterial toxins?
- A = enzymatic subunit
- B = binds to host cell receptors
Define extracellular bacteria.
Bacteria that live outside of host cells and release toxins.
What is the primary purpose of viral proteins?
- To replicate the genome
- To package and deliver the genome to more host cells
- To modify the structure or function of the host cell
List the six steps of viral replication.
- Entry into the host cell
- Disassembly of the infectious virus particle
- Replication of the viral genome
- Transcription of viral genes and synthesis of viral proteins
- Assembly of these viral components into progeny virus particles
- Release of progeny virions
How do enveloped viruses acquire their envelopes?
By budding off from the cell’s plasma membrane.
What are the common tasks for all pathogens?
- Gain access to the host
- Reach an appropriate niche
- Avoid host defenses
- Replicate
- Exit from the infected host
How do pathogens overcome epithelial barriers?
Via adhesions such as proteins or protein complexes (pili) that recognize and bind to cell-surface molecules.
True or False: Extracellular pathogens enter host cells.
False.
How do viruses enter host cells?
By membrane fusion, pore formation, or membrane disruption.
What are the two primary mechanisms bacteria use to induce phagocytosis?
- Zipper mechanism
- Trigger mechanism
What is an example of an intracellular eukaryotic parasite?
Toxoplasma gondii.
What must intracellular pathogens do after entering a host cell?
Find a compartment that they can survive and replicate in.
What do many pathogens alter in the host cell to survive and replicate?
Vesicular transport.
What are PAMPS?
Pathogen-associated molecular patterns, such as peptidoglycan and LPS.
