Question

Medical Microbiology Tutorial: Social Behavior in Pathogens

Answer 1

\({\bf{Definitions:}}\)
Signal: something (can be a physical thing like a compound, or a behavior) that changes the behavior of another organism
- in order to be classified as a signal, the production of the signal and the response must have arisen through evolution (otherwise, it's considered a cue).
- generally benefits both the producer and the recipient

Reasons for Social Behavior in Pathogens?
- produce VFs
- overcome host defense systems
- migration
- form biofilms

Answer 2

\({\bf{Quorum~Sensing:}}\) the production of signal molecules (autoinducers, pheromones) and the corresponding response to the change in signal concentration



model system: V. fischeri in squid --> quorum sensing leads to bioluminescence
some terms to go over:
> luxR: the protein that regulates transcription
> luxI: the protein that synthesizes the signal molecule AHL
> AHL (n-acyl homoserine lactone): the signal molecule that binds to luxR and activates transcription of the bio-luminescence genes

as luxI produces AHL, AHL is exported outside the cell, where other V. fischeri can potentially respond to it by synthesizing AHL and activating the bioluminescence genes

Answer 3

\({\bf{P.Aeruginosa~QS~System:}}\) regulated by rh and las systems (this is *extremely* complicated and not worth memorizing but you should probably know a few of the characteristics that result from this system: exotoxin, protease, biofilm formation/maturation, secretion systems, swarming

Answer 4

\({\bf{Cooperation~and~Cheating:}}\)

cooperation: social behavior in which one organism performs a behavior, at individual cost, that benefits others
cheating: social behavior in which one organism exploits the resource created by cooperation without contributing back

likethepeopleonQCwhoactuallyhelpvsthepeoplewhoasklikeabajillionquestionsandneverhelpothersahem

public good: resource produced at individual cost and group benefit
examples: siderophores, beta-lactamases, toxins, etc.

when comparing a cooperators-only population vs. a cheaters-only population, cooperators are better off, but combining them, cheaters can surpass cooperator growth (to a certain point, as long as the cheater phenotype doesn't exceed a certain frequency)
- example of negative-frequency dependent selection

Answer 5

\({\bf{Quorum~Quenching:}}\)
- inhibition of social behavior is one approach to fighting infection
- advantages: harder to evolve resistance, doesn't release as many endotoxins

4 methods of decreasing virulence, based on quorum quenching:
- destroy/inactive the signal molecule
- destroy/inactivate the signal synthesis
- inhibit the interaction between signal and receptor
- stop translation of QS genes

Answer 6

\({\bf{Sources:}}\)
- lecture notes
https://www.frontiersin.org/articles/10.3389/fmicb.2018.01354
https://www.ncbi.nlm.nih.gov/pubmed/9150205
https://www.frontiersin.org/articles/10.3389/fmicb.2013.00356/full
https://www.researchgate.net/figure/Quorum-sensing-bioluminescence-system-of-V-fischeri_fig1_291206395
https://www.researchgate.net/publication/291206395_Interfering_with_Bacterial_Quorum_Sensing
https://www.ncbi.nlm.nih.gov/pubmed/11544353
https://phys.org/news/2018-06-cheatersexploring-bacterial-social-interactions-pathogens.html
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5648865/

Answer 7

VFs stands for ??

Answer 8

virulence factors

Answer 9

I see. ty
Do you read the entire ncbi articles for all the topics ???

Answer 10

not for the purposes of making a tutorial, they're just for basic facts + definitions