Lecture Notes quorum sensing

*Quorum Sensing - Ability of some bacteria to change phenotype at different population densities.

* Genotype: set of expressed traits that have genes/ DNA

* Phenotype: physical set of characteristics that are seen

Eg.) Quorum sensing phenotype - suicide at high population densities

# 1 S. pneumoniae : Genes for signal receptor are always on.
When signal receptors ar efull Lyta gene is expressed
Lyta protein kills bacteria from inside out

# 2 Pseudomonas aerguinosa: makes biofilm ( made of rhammolipids, pyocynin) it's made at high population densities.
When all all signal receptors are full the genes for rhammnolipids and pyocyanin are
expressed.

# 3 Vibrio Fischeri: Lives in salt water, expresses luciferase at high population densities that emit blue - green light.
Genes for signal receptor always on, when all receptors have signal homoserene lactone bound to
them, genes for luciferase are expressed.

  • Vibrio Fischeri relationship with squid - Eurypmna Scolopes (squid) is nocturnal. It is a prey to large animals and predator to small, but it's shadow can intervene. When the moon shines the squid's shadow is cancelled out. The squid has light organ in it's head that when colonized with vibrio fischeri allows high population density of V. fischeri - luciferase
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