Sociality and cheating in bacteria
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Transcript of 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
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?
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)
Quorum sensing
Modes of communication
Evolution of cooperation +/or selfish behavior
• System: Myxococcus xanthus
• Primary Investigator: Greg Velicer
Myxococcus xanthus
http://cmgm.stanford.edu/~kaiserla/about_myxo/about_myxococcus.html
• Adventurous motility• Social motility• Gliding motility• Development of spores
• Motility can be A = adventurous or S = social
• A motility = dependent upon gliding and slime extrusion
• S motility = dependent upon type IV pili
First experimental evo of Myxo
• 12 populations, 6 RifR, shaking flasks, CTT (rich) media.
• Inhibits social contact; mass-action
But the selfish asocial evolved lineages cheat…
Cooperation can evolve along multiple pathways
Cooperation re-evolves using a new system
• cglB = A motility gene
• dsp = fibril producing gene