Lecture 2 Flashcards
(50 cards)
What must bacteria maintain and why?
Bacteria must maintain a reservior.
Some bacterial pathogens can move from human to human, human to animal but many don’t.
Do pathogens spend extended periods of time in the external environment
Yes
What are some major issues with bacteria maintaining a reservoir?
- Availability of essential nutrients
- Lack of adherence sites or niches similar to hosts (Surviving in amoeba is similar to immune cells)
- Exposure to noxious chemicals/predators
- Exposure to sunlight and extreme weather (Thermal shifts)
What are some survival strategies for bacteria?
- Endo-sporulation (Gram positive)
- Desiccation resistance (Gram Negative)
-Metabolic versatility - Dormancy
- Genome plasticity
- Colonize another host
- Alter membrane properties
- Xenobiotic efflux
- Biofilm formation
What is endo-sporulation (gram positive)
What is desiccaton resistance (Gram negatvie)
The cell not drying out, there are molecules that bacteria produce that help them retain water and resist the absence within cells
What is metabolic versatility?
What is dormancy
A way that bacteria responds to starvation, they can survive for extended periods of time without external nutrients
What is genome plasticity
Where bacteria can rearrange their genes in a particular way; they can acquire new things and/or survive in a new host.
What does colonize another host mean
What is motility and chemotaxis?
What does it mean to alter membrane properties
To shift composition of the cell envelope in a particular way to survive within the presence of particular chemicals
What is xenobiotic efflux
Taking a toxic compound and blow it outside of a cell.
What is biofilm formation
- Can act as a reservoir to many bacteria
-viewed as a developmental and social process that is functionally analogous to differentiation in multicellular organisms
Explain biofilm formation
- Many bacteria form biofilms
- They are dense, multiorganismal layers of bacterial communities attached to surfaces
- Biogilm protect against antibiotics, disionfectants, phagocytic attack and more
- Bacterial attachment to surgace.each other is mediated by polysaccharide slime, which acts like a glue
What is biofilm matrix polymers and what do they do
What is Molecular Koch’s postulates
This is proof that a gene product is an essential virulence factor
What are the steps of Molecular Koch’s postulates?
- The pathogenic trait should be associated with the pathogenic members of the genus, species or strains
- Inactivation of the gene associated with the pathogenic trait should result in a measurable loss of pathogenicity or virulence
- Reversion of allelic replacement (complementation) of the mutated gene should restore pathogenicity
What is an example of molecular Koch’s postulates
This is more than an organism infecting a host.
- Start by inactivating the gene that’s linked to the specific trait, you would knock out the gene from the protein and show there is a virulence-associated phenotype in an animal model.
Then replace the allele back inside bacteria and it would restore virulence (This is important because it confirms that genetic linkage is sound and there is no mutation that occurred)
How do we evaluate virulence factors?
By compairng the ability of the wildtype and mutant bacteria to survive in a host and cause disease
What are the 4 steps we use to evaluate virulence factors?
- dilute bacteria to known concentration
- Infect host (assess the success of initial inoculation)
- Allow animals to get sick (wild type takes a few days)
- Harvest organs and assess bacterial growth and pathology
What are the 5 common steps in bacterial infection
- Entry to the host body for colonization
- Migration to a niche
- Often requires attachment - Evasion of host defenses (innate and adaptive)
- Obtain nutrients, multiply to significant numbers, and spread
- Damage the host and produce disease
- Direct damage due to toxins of the bacteria
- Collateral damage due to immune response - Transmission from infected to susceptible host
Explain (1) entry into the host and the ways it occurs
There is no known bacterium tha can penetrate human skin.
Entry occurs via:
Wounds and burns
Insect bites
Ingestion of tainted foods
The eyes
Inhalation
Genitourinary tract
Explain motility and taxis in relation to entry into the host
