Bacterial Pathogenesis 1 Flashcards
Transduction vs transformation vs conjugation
Transformation: kill and uptake
Transduction: Phage
Conjugation: sex pili
Two naturally competent bacteria
Bacillus subtilis and strep pneumo (Nat. competent usually only take up linear DNA, not circular or from phages)
Bacteria that only transform their own genus
H. Influenza and Neissera Gonorrhoeae
A transducing phage transfers DNA during the…
lytic phase
What two organelles assist in gene transfer in conjugation?
Relaxasomes and Transferasomes
F plasmids
contain “tra” genes for transfer. Result in sex pili
Col plasmids
contain bacteriocins (proteins to kill bac) or genotoxins (kill host cells)
mob plasmids
can only transfer by hitchhiking along with other plasmids that contain tra genes
Pathogenicity islands
10-200kb and have different G+C% content than rest of the bac chromosome
EPEC and EHEC
Enteropathogenic and enterohaemorrhagic E. Coli. Attach to actin pedestals and inject molecules into the host cells
Facultative intracellular bacteria
have genes that control virulence factor expression so they can survive both inside and outside of host cells
Enzymes that destroy cell defences, made by extracellular bacteria
chemokines, sIgA
How intracellular pathogens are different
- resistant to Reactive OS and NO, (superoxide dismutase, SOD, made by Staphylococci and salmonella) (Listeria suppresses NO synthase expression in host)
- Legionella and Mycobacterium prevent phagolysosome fnx
- Listeria, Francisella, and Rickettsia escapre phagosomes
Listeria
Gram+ facultative anaerobe. 3rd leading cause of death due to food poisoning. Uses genes like plcA and hly. These lead to InIA and InIB make non-phagocyte cells to phagocytose bacteria (muahahaha!) by changing actin cytoskeleton
What nutrients are in high demand in the body?
- Metals/cations (Fe, Mn, Zn, Cu, Mo)
- Amino Acids
- Carbs
- O2 and other election acceptors
Three ways that bacteria avoid dying from lack of amino acids inside a cell
- M. Tuberculosis makes its own tryptophan
- C. Trachomatis turns reticulate bodies into aberrant bodies
- L. pneumophila uses ankB and polyUb to use host as a food source
Enterobactin
a molecule made by bacteria to steal iron from host. Host counters with lipocalin which breaks down enterobactin. Bacteria counters by glucosylating enterobactin.
Salmonella
Cause typhoid (enteric fever, humans only) and gastroenteritis (non-typhoid, affect many animals)
Salmonella PA1-encoded effectors
trigger host membrane ruffles that envelope and internalize bound bacteria
Toxin types
I- bind and act as host cell surface (super antigens)
II- Act on host cell membrane (phospholipase and pore-forming toxins)
III- A-B type toxins, includes single chain (DT and BoNT) and multisubunit toxins (cholera and anthrax toxins)
Other ways to categorize toxins
- non-protein vs protein
- Endotoxin vs exotoxins
- effector proteins
Non-protein toxins
aka Endotoxins. Stimulate TLR4 or TLR2/6. Lead to septic shock, DIC or Acute respiratory system
Mycobacterium ulcers makes a ____ toxin called _____ that does _____
non-protein, polyketide-derived mycolactone, Buruli ulcers (necrotic lesions)
Superantigens bind ____ outside the peptide cleft
MHC II. T cells are activated and then exhausted and die, inflammation goes crazy. Spread by diarrhea
Staph Aureus
- 1/3 of population is colonized
- thrives in hospital (HA-MRSA)
- Daycare and wrestlers (CA-MRSA)
- Causes food poisoning, sepsis, abscesses, and cellulitis, bacteremia/sepsis
- Surfaces have adhesins, capsule, Protein A, MSCRAMMS
Protein A
binds IgG
Toxic Shock Syndrom toxin 1
TSST-1, superantigen (superabsorbent tampons that grew staph aureus)
AgrC and AgrA
Sensor Kinase and Response Regulator (Hamemelitannin from witch hazel inhibits MRSA quorum sensing)
E. Coli can sense
Adrenergens in the body
Phospholipases
-a toxin of C. perferingens: hydrolyzes the lipid lecithin, contributes to gangrene
Pore-formin toxins
- Alpha (helixes)
- Beta (barrel)
- These represent about 30% of the toxins
- Eg Aerolysins (inserts itself spirally)
A/B toxins
A subunit is responsible for the enzymatic activity, B mediates binding
How do A/B toxins enter cells?
- Fuse with endosomes (DT, BoNT)
- Retrograde transport (cholera and shiga toxin)
Cholera Toxin does what?
produces abnormally high cAMP levels, cause more Cl- to be produced in gut. Diarrhea, dehydration, loss of electrolytes.
What is Diptheria?
Colonization of throat by Corynebacterium diphtheriae. G+, non-motile, aerobic. Only in humans. Causes a pseudomembrane in throat and lungs; removal can make you bleed, can make you choke.
How does DT enter cells?
Heparin-binding epidermal growth factor (HB-EGF)-like receptors. These are present in the heart and nerve cells in large numbers
Toxoids
non-toxic version of a toxin, used in a vaccine. Can affect children and adults
