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Sociality and cheating in bacteria

Sociality and cheating in bacteria. Lecture 13, Myxobacteria. Evolution of social and coordinated group behavior in bacteria. Swarming motility Quorum sensing Coordinated cell death Sporulation and fruiting body formation Synergistic niche subdivision Production of “ social goods ” etc.

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Sociality and cheating in bacteria

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  1. Sociality and cheating in bacteria Lecture 13, Myxobacteria

  2. Evolution of social and coordinated group behavior in bacteria • Swarming motility • Quorum sensing • Coordinated cell death • Sporulation and fruiting body formation • Synergistic niche subdivision • Production of “social goods” • etc

  3. All for the benefit of the group, right? • Why broadcast a signal for others to profit from your discovery? • Why allow foreigners to listen in on your conversation? • How would such behavior evolve?

  4. Individual selection favoring functions that coordinate groups • Inability to produce a beneficial phenotype in small numbers • Numbers of neighbors producing a signal may not matter as much as their density • Common response by several traits to high density or numbers, so selection favors their coordination (and not vice versa)

  5. Quorum sensing

  6. Modes of communication

  7. Evolution of cooperation +/or selfish behavior • System: Myxococcus xanthus • Primary Investigator: Greg Velicer

  8. Myxococcus xanthus http://cmgm.stanford.edu/~kaiserla/about_myxo/about_myxococcus.html • Adventurous motility • Social motility • Gliding motility • Development of spores

  9. Motility can be A = adventurous or S = social • A motility = dependent upon gliding and slime extrusion • S motility = dependent upon type IV pili

  10. First experimental evo of Myxo • 12 populations, 6 RifR, shaking flasks, CTT (rich) media. • Inhibits social contact; mass-action

  11. But the selfish asocial evolved lineages cheat…

  12. Cooperation can evolve along multiple pathways

  13. Cooperation re-evolves using a new system • cglB = A motility gene • dsp = fibril producing gene

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