Experimental social evolution with Myxococcus xanthus |
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Authors: | Velicer Gregory J Stredwick Kristina L |
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Institution: | (1) Department of Evolutionary Biology, Max-Planck-Institute for Developmental Biology, Spemannstrasse 37, D-72076 Tuebingen, Germany;;(2) Department of Microbiology, Michigan State University, East Lansing, MI 48824, USA |
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Abstract: | Genetically-based social behaviors are subject to evolutionary change in response to natural selection. Numerous microbial
systems provide not only the opportunity to understand the genetic mechanisms underlying specific social interactions, but
also to observe evolutionary changes in sociality over short time periods. Here we summarize experiments in which behaviors
of the social bacterium Myxococcus xanthus changed extensively during evolutionary adaptation to two relatively asocial laboratory environments. M. xanthus moves cooperatively, exhibits cooperative multicellular development upon starvation and also appears to prey cooperatively
on other bacteria. Replicate populations of M. xanthus were evolved in both structured (agar plate) and unstructured (liquid) environments that contained abundant resources. The
importance of social cooperation for evolutionary fitness in these habitats was limited by the absence of positive selection
for starvation-induced spore production or predatory efficiency. Evolved populations showed major losses in all measured categories
of social proficiency- motility, predation, fruiting ability, and sporulation. Moreover, several evolved genotypes were observed
to exploit the social behavior of their ancestral parent when mixed together during the developmental process. These experiments
that resulted in both socially defective and socially exploitative genotypes demonstrate the power of laboratory selection
experiments for studying social evolution at the microbial level. Results from additional selection experiments that place
positive selection pressure on social phenotypes can be integrated with direct study of natural populations to increase our
understanding of principles that underlie the evolution of microbial social behavior.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | behavior cooperation evolution predation Myxococcus social |
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