Features of Gram + Bacteria

• TA
• Thick Peptidoglycan
• 1 membrane
• More susceptible to antibiotics that directly target the cell wall
• Less susceptible to lysis

chemoattractant

Peptide that attracts PMNs to site where bacteria are growing

NLR - bacterial lipid/cell wall

RLR - viral RNA

– Series of protein that circulate in an inactive form.
– Once activated: recruit phagocytes (PMNs), promote
phagocytosis (opsonize), promote inflammation, and can lyse bacteria

Cysteine-rich peptides with 3 disulfide bonds. 

What is Koch's 1st postulate?

1. Virulence gene should only be found in disease causing strains of bacteria, not in avirulent varients

2. The gene should be "isolated" by cloning

3. Disruption of the gene should reduce virulence (attenutation)

4. Introduction of th cloned gene avirulent strain should render new strain virulent. Most stringent when complementation of original mutation with wt gene restores virulence in mutant strain.

Macrophages, DCs, and other APCS 

Target: Extracellular bacteria

antigen-presenting cell

macrophages, DCs, and B cells

Produce: IFN-y

Activate: macrophages

Stimulate (Th2): B cells to produce antibodies

Lipid or glycolipid

-ex. Mycobacterium tuberculosis

PMNs → IL-12 which stimulates NK cells → IFN-y

Use: CTL activation, inflammation

CONTROLS INTRACELLULAR BACTERIA

IL-4

Use: activate eosinophils, IgG1, IgE for opsonization & some downregulation

Clears EXTRACELLULAR bacteria, parasites (metazoal)

Mech. of Genetic Change & Diversification in Bacteria

What are some examples of slow vs rapid processes?

slow: point mutations, gene duplication (evolutionary processes)

rapid: phase variation (slipped strand synethesis), antigenic variation (gene shuffling) conjugation, transduction

• Regulatory mechanism for rapid alteration of bacterial gene expression (usually virulence factors)
• Allows for quick response to varying environments and conditions

Several mechanisms:

ENZYME: hin (DNA invertase)

Promoter controls switch from H1 to H2 flagellin protein and back again by releasing a repressor

Neisseria

Carry silent copies of gene which can be incorporated into active gene

Allows permanent change of pilE

what type of bacteria use promoter methylation?

Define slipped-strand synthesis and give example of what bacteria use it.

It's a reversible mutation (causes frameshift) to turn on/off toxin & other virulence factors

bordatella

Horizontal gene transfer

-ways to acquire new genes in a matter of hour (anbiotic resistance, toxins)

-contribues to genome variability

• Transformation
• Conjugation
• Transposons
• Transduction

through HGT

Improves virulence factors (adhesion)

DNA taken up directly by cells (usually linear, not plasmids)

Streptoccuspneumoniae

Griffith gave R and S strain to mice found that live R strains can transform heat killed S strain = mouse dies.

-attach to host (COLONIZATION)

-evade innate & adaptive

outcompete commensals

-aquire limiting nutrients (iron)

-transmit to new host

extracellular: posess virulence factors that prevent uptake & destruction by phagocytes

intracellular: promote factors to allow survival in inhospitable environment

Or balance between location and regulate virulence factor expression