From encounter to disease - Bacteriology I Flashcards
Contains the lectures from Willem and about pneumococcal infections
What is a factor to determine if bacteria are primitive?
Organization the cell itself
What are two-component systems?
Systems that carry out signal transduction
What are the two proteins of the two-component regulatory system
- Sensor kinase
- Response regulator
What is the function of a sensor kinase?
Detects environmental signal and autophosphorylates
What is the function of a response regulator?
DNA-binding protein that regulates transcription
Describe the possibility of the dual function of response regulators
Response regulator can be activating and inhibitory of the RNA polymerase –> transcription activated/inhibited
How many two-component systems can be found in E.coli?
50
Examples of two-component systems in E.coli
- Phosphate assimilation
- Nitrogen metabolism
- Osmotic pressure response
Describe the osmotic component system in E.coli
What are two-component systems important for?
Monitoring and responding to changes in the bacterial environment
Can you see a Campylobacter under your microscope if they are active? Why/why not?
No, they are way too fast. You have to numb them.
What happens to the movement of bacteria if there is a absence/presence of attractants in their surroundings?
Absence: random movement
Presence: directed movement
Why two kinds of movement are there for flagellated bacteria?
- Peritrichous
- Polar movement
How does peritrichous movement work?
- Bundled flagella (CCW rotation). —>
- Flagella pushed apart (CW rotation) <—>
- Flagella bundled (CCW rotation) <—
Which division is important to make in polar movement of flagellated bacteria?
If a bacterium has a reversible- or unidirectional flagella
Orientation of movement of bacteria with: one flagella
Can move their flagella clockwise or counter clockwise
How does polar movement for bacteria with reversible flagella work?
- CCW rotation —>
- CW rotation <—
How does polar movement for bacteria with unidirectional flagella work?
- CW rotation —>
- Cell stops, reorients
- CW rotation upwards
How do they sense their surroundings?
Two component system used in chemotaxis
How is the two-component system used in chemotaxis? (3)
- Sense temporal changes in attractants or repellents
- Regulate flagellar rotation
- Regulate activity of pre-existing proteins
Definition of taxis
Directed movement in response to chemical or physical gradients
Different kind of ‘taxes’ (5)
- Chemotaxis - chemicals
- Phototaxis - light
- Aerotaxis - oxygen
- Osmotaxis - ionic strength
- Hydrotaxis - water
True or false: “Bacteria can actively search for targets”
True. Chemotaxis
What are endospores?
Survival structures to endure unfavorable growth conditions
Why are endospores perfect for bacteria that don’t have a flagella?
This ensures a perfect way to be spread
How are endospores spread?
Ideal for dispersal via wind, water, or animal gut
In what kind of bacteria can you find endospores?
Present only in gram-positive bacteria, (e.g., Bacillus and Clostridium)
Describe the sporulation stages (7)
- Normal division
- Commitment to sporulation –> asymmetric division
- Spore is formed in the bug
- Forms all kind of covers and stuff to penetrate materials
- Bacterial cell lyses
- Free endospore
- Germination
Name an example of a disease that can occur due to endospores
Antrax infection in the lungs
What does the endospore package contain?
DNA needed to form a new bacterium
Describe the maltose catabolism in E.coli
Protein needs to bind maltose to form a complex on the activator site, RNA polymerase can bind –> machinery to metabolize maltose
What is catabolite repression?
Global regulating system: controls use of carbon sources if more than one presents
Catabolite repression is also called the “glucose effect”. Why?
Because the synthesis of unrelated catabolic enzymes is repressed if glucose is present in growth medium
What is diauxic growth?
Two exponential growth phases if two energy sources are available
How does diauxic growth work?
- Better energy source consumed first, growth stops
- After lag, growth resumes with second energy source
What controls transcription in catabolite repression? How?
Cyclic AMP receptor protein. CRP binds to DNA only if it has bound cyclic adenosine monophosphate
How is the inactive repressor generated to make lactose?
- CRP/cAMP binds to operator and blocks transcription
- Lacl is transcribed and translated
- Active repressor
- Inducer binds to AR
Catabolization of a certain sugar by a bacterial cell depends on… (2)
- Presence of the metabolite
- Metabolic status of the cell
What can influence the presence of a metabolite?
Presence of other sugars
What is quorum sensing?
Mechanism by which bacteria assess their population density
What does quorum sensing ensure?
That a sufficient number of cells are present before initiating a response that, to be effective, requires a certain cell density
Name an example of a virulence factor of ‘E.coli O157:H7 shiga toxin–producing strain’ involved in quorum sensing?
Produces AHL AI-3 that induces virulence genes
What does AL-3 bind to and where?
Sensor molecules in plasma membrane.
What is the result of AL-3 binding to sensor molecules in the plasma membrane? (3)
Activation of
- Motility
- Toxin secretion
- Production lesion-forming proteins
Name an example of a virulence factor of S.Aureus involved in quorum sensing?
Secretes small peptides that damage host cells or alter host’s immune system
What controls this secretion of small peptides in S.Aureus?
Autoinducing peptide (AIP)
What are potential drugs preventing virulence gene expression?
Quorum-sensing disruptors
What are stringent responses?
Stress response in reaction to amino acid starvation
Name an example of a stringent response in E.coli?
Voiding E. coli in feces reduces nutrients –>initiates ppGpp synthesis –> arrested cell division
Name an example of a stringent response
Lungs hypoxic and phosphate-limited
Function of the TATA box
Stable binding on the promoter
Name two global control systems
- Heat-shock response
- RpoS regulon
What is the function of the heat-shock proteins?
Counteract damage of denatured proteins and help cell recover from temperature stress
How are heat-shock proteins induced?
Induced by heat, exposure to ethanol or ultraviolet (UV) radiation
What factor largely controls the heat-shock response?
Alternative sigma factor RpoH
What factor largely controls the RpoS regulon?
Stationary phase sigma factor
What kind of infections can be caused by Streptococcus bacteria?
- Pneumonia
- Meningitis
- Otitis media
What kind of bacterium is S. pneumonia?
Gram-positive, microaerophillic coccoid bacterium (diplococcus)
Describe the lifecycle of S. Pneumonia (3)
- Colonization of epithelium
- Transmission/Shedding
- Invasion
Where does colonization of S. Pneumonia happen?
Nasal epithelium
Describe the three options of invasion of S. Pneumonia
- Aspiration (lungs)
- Bacteraemia (brain)
- Local spread (ear)
How can the general epidemiological curve of incidence be described? (pneumococcal infections)
U-curve (infants and elderly)
Which factor can really influence the epidemiological curve?
Co-infection
Which factors play a role in the onset of a co-infection? (4)
- Epithelial cell damage
- Decreased mucociliary velocity
- Reduced CCL2 expression
- Reduced macrophage functionality
How can you perform an etiological diagnosis of pneumococcal infections? (4)
- Isolation from URT, blood, sputum, CSF
- Culture and characterization
- PCR/MALDI-TOF
- Bile solubility test
What is the transformation principle?
DNA crossed over from the virulent strain to the non-virulent strain
Advantage of the pneumococcal capsule
Capsule protects bacterium in the bloodstream against the immune system –> resistance against phagocytosis
Describe the biosynthesis of the polysaccharide capsule
- Every sugar structure has repeating units
- New sugar that has to be added (specific for sugar) is flipped outside and attached to peptidoglycan
Techniques used to determine genetic variation amongst S. Pneumonia? (2)
- Multi-locus sequence typing
- Whole genome sequencing
How can a non-competent cell become competent? How is competence induced?
Horizontal gene transfer induced by environmental signals (high cell density, stress)
What does competence lead to?
Killing of neighboring cells
Which proteins can be found in the pneumococcal cell wall? (4)
- Phosphorylcholine binding proteins
- Peptidoglycan binding proteins
- Classical surface proteins
- Lipoproteins
What is the function of ABC transporters?
Niche adaptation
What is essential for the induction of inflammation? What does this phenomenon lead to?
Pore formation. Leads to faster clearance and increased transmission
Which additional factors influence transmission if you are a nasal carrier of S. pneumonia? (5)
- Pneumolysin
- Capsule type and amount
- Anticapsule IgG
- Anticapsule IgA1
- Viral co-infections
Function of pneumolysin in transmission of s.pneumonia? (2)
- Increased shedding
- Inflammation promotes secretions
Capsule type amount
- Increased shedding
- Inhibition of mucin entrapment
Anticapsule IgG
- Decreased shedding
- Agglutionation blocks release
Anticapsule IgA1
- No effect on shedding
- Bacterial protease relieves agglutination
Viral co-infection
- Increased shedding
- Increased bacterial load and mucus production
Which factors influence the prominence of S. pneumonia as a cause of disease? (3)
- High carriage rates
- Genetic adaptability
- Ability to shift from commensal to pathogenic interaction with host
From colonisation to invasive disease requires niche adaptation. Name two ways of niche adaptation
- Metabolic adaptation
- Immunological adaptation
What is meant with metabolic adaptation?
Maintenance of metal levels, different carbon sources
What is meant with immunological adaptation?
From non-sterile to sterile site
