Article 1: Mindless Talks

• Bacteria

  • Primitive and mindless
  • Able to communicate, always precise, methodical, coordinated, and ensuring the utmost benefit of the population
• Quorum Sensing - microorganisms' sophisticated type of social communication
• Quorum Sensing - language of bacteria in the form of chemical signals which they release
• First glimpse of quorum sensing - 1965 by Alexander Tomasz - used bacteria causing pneumonia
• 1970 - Nealson, Platt, Hastings, Nocturnal Hawaiian bobtail squid
• Nocturnal Hawaiian Bobtail Squid

  • bioluminescent
  • the light is emitted by Vibrio fischeri living underneath the skin of the squid
  • Symbiosis relations
• Cell Density - determines the factor that triggers bioluminescence
• Acyl-homoserine Lactone (AHL) - excreted chemical signal; autoinducer

  • Enough concentration of this can bind to another protein which triggers the expression of the set of genes for bioluminescence called lux.
• Lux genes - genes that encode enzymes that catalyze the conversion of light energy into chemical energy.
• Virulence - ability to defeat the defense system of their host
• Pathogenic or infectious disease-causing bacteria are also very dependent of quorum sensing in order to successfully launch virulence
• EP Greenberg

  • coined quorum sensing
  • identified the phenomenon in the virulence of the bacterium Pseudomonas aureginosa
  • Infects immunocompromised patients or those who are suffering from diabetes, AIDS, or cancer because it has an impressive armament of toxins that are so fatal that they overcome the immune system
• Biofilm

  • formed by bacteria
  • compact thin strip
  • persist by quorum sensing
  • excrete a slimy protective shield against several competing microorganism and antibiotics
• Pseudomonas aeruginosa - produces proverdine which is a siderophore
• Siderophore - a molecule which bacterium sends out to its environment to scavenge and shuttle iron back into itself
• Keith Poole - found that pyoverdine also plays a crucial role in quorum sensing.
• • Lack quorum sensing - low production of pyoverdine
  • Increased production of pyoverdine - increased the production of toxins
• • Vibrio fischeri excretes AHLs as chemical signals to communicate; 
  • Pseudomonas aeruginosa uses both AHLs and the siderophore pyoverdine
  • Other bacteria uses peptides or short proteins
• Autoinducer-2 - widespread in the microbial world facilitating interspecies communicaton