Sociomicrobiology Flashcards
What is Sociality?
Interaction between two or more individuals, measurable as either cooperation or conflict.
What is Sociomicrobiology?
The Old view: Bacteria Prove that sociality is a consequence of size and complexity
The New view: Bacterial Sociality Is important just like sociality in higher organisms
Why do we work on sociomicrobiology?
Models to understand biology of sociality
understanding bacteria
to develop new medicines to treat devastating bacterial infections
What is quorum sensing? What is the most studies variation of quorum sensing?
Quorum sensing is cell-cell signaling used to control specific genes and allows coordination of group activities
The most studied system is the acyl-HSL sensing in proteobacteria. Signals are made by the LuxI family and receptors are the LuxR family.
Quorum sensing vocabulary
Signals: Act as a structure or chemical emission that alters behavior of another organism. Evolved because of that effect and is effective bc the receivers response has co-evolved.
Cues: An act, structure or chemical emission that alters behavior of another organism, it did not evolve to that effect.
Chemical manipulation: Chemical emission that alters behavior of other organisms but has a negative effect on the fitness of the receiver
What key organism uses Acyl-HSL signaling?
Vibrio Fischeri!!!!
converts chemical energy to light at high population density
found In plankton, in sea water at low density
How does Vibrio Fischeri do symbiosis?
The Ngai and Ruby squid has vibrio Fischer surrounding its ink sack. Fischeri are a light organ with a high population density that can make light for the squid that counteracts moonlight to hide shadow at night. V. Fischeri has genes A-E for bioluminescence.
What is the mechanism of quorum sensing?
V. Fischer have luxI that makes AHL in high population density. AHL binds to luxR (transcription factor) that triggers bioluminescence.
When there is a low population density, AHL will diffuse out.
What is ACL? Describe about other cell signals and where they occur.
AHL is acyl homoserine lactone and there are various versions for unique bacteria, with unique receptors. Proteobacteria make AHLs. Gram positive bacteria like S. Aureus make cyclic peptides, whereas B. SUbtilis will make a linear peptide with unique amino acids. streptomycetes make an antibiotic.
Why do bacteria communicate?
Light production in V.Fischeri- no individual makes enough for biological detection, its a group effort WITH FREELOADERS.
- exoenzymes: bacteria makes them and they break down large molecules with protease.
Pseudomonas Aeruginosa
P. Aeruginosa senses cell density through quorum sensing
Low bacterial density, low QS signal-> little activation of QS-controlled virulence and bioofil
–> Opposite for high bacterial density
Uses two quorum sensing signals
- > C-12 HSL made by LuxI and responded to by LuxR
- > triggers signal cascade of C4-HSL made by RhlR-RhlI
Why are Las R mutants common in certain infections?
They’re free loaders!
Case Study of gram positive quorum sensing: S-Aurues agr system
No AHL but have quorum sensing-> Convergent evolution
Has auto inducing peptide (AIP)- monitors cell density
When cell density increases, signal reaches a critical threshold and up regulates extracellular virulence factors and down regulates surface virulence factors
Molecular Scheme of S-Aureus quorum sensing
Temporal regulation of virulence factors: Early events (low AIP): Colonization factors expressed, S.Aureus grows in aggregates Middle events (AIP activates RNAIII): colonization factors repressed Late events (AIP activation Plus): Virulence Factors expressed
