Lecture 2 - Being competitive in the host Flashcards
Give some features of bacterial genomes
Plasmid or megaplasmids
Contain remnants of phage (lysogenic phage) which acquire mutations
Always acquiring and losing DNA (horizontal gene transfer)
Core genome and pan genome
What is reductive evolution?
Give an example of a bacteria that’s gone through it
Gene loss of pseudogenes when pathogen has very stable environment
Lepri
What are the major players in genome evolution?
Chromosomal rearrangements (strong promoters added, genes duplicated and changed) SNPs
What other kinds of genes do pathogens need other than virulence factors?
Competition for carbon nutrition
Where does B. theta live and what does it use as a carbon source?
In our gut and uses glycans on mucin proteins in mucus between epithelial cells and food
How does nutrient availability and environment change through the gut?
In the small intestine there’s more food and starch is easy to break down
Large intestine is anaerobic and pH 5.5, source shifts from dietary components to mucus layer
What happens when you are starving?
Commensal gut bacteria more stressed so more likely to get an infection
What does the body do when you’re starving?
Make more fucosylated glycans to feed commensal bacteria to keep them happy
What does the microbiota give back to us?
Short chain fatty acids for energy
How many carbon sources can E.coli use?
about 20
What experiment did Leathametal do?
Precolonised gut with some commensal strains of E.coli which protected the mouse against infection by some pathogenic strains
What is a pathogenicity island?
cluster of coregulated genes which tends to insert at genes for tRNAs
What are the nan-nag genes?
V. cholerae’s mechanism for taking up sialic acid - with out it its much less likely to cause infection
What experiments were done with the nan-nag genes?
In mouse early colonisation is defective when pathogenicity island containing nan-nag gone
What does B. theta do in the gut?
Has a sialidase but has no genes to break down sialic acid
Allows it to get to complex sugars underneath
In an experiment what is the gut like with out B.theta?
No free sialic acid
How does C. difficile use sialic acid?
Nan genes induced in presence of B. theta
What is the relationship between C. difficile and B. theta?
More C. diff when coinfected with B .theta
