social evolution in microbes

Social Evolution In Microbes

It is an extremely exciting time for researchers interested in the social behaviour of microbes. Microorganisms exhibit a stunning array of social behaviours, such as dispersal, foraging, biofilm formation, chemical warfare, and quorum sensing. These behaviours are provoking interest both in their own right, and also because of the implications that follow from the fact that many of these behaviours are involved in bacterial virulence.

Interest in the social behaviour of microbes is coming from two directions. Microbiologists are rapidly gaining a greater understanding of the molecular mechanisms involved in these behaviours, and the underlying genetic regulation. Evolutionary biologists are becoming increasinly interested in microbes, because they offer some novel problems, as well as exceptional opportunities for testing evolutionary theory. In particular, explaining cooperation and communication remain two of the greatest problems for evolutionary biology.

Our main findings include:

We have shown that Quorum sensing is a cooperative social behaviour, which can be exploited by cheats and that a potential solution to this problem is cooperation between relatives (kin selection) - both in test tubes (Diggle et al. 2007 Nature) and mice (Rumbaugh et al. 2009 Current Biology). Our mice work also allowed us to examine the virulence consequences of social interactions.
We have reviewed how social evolution theory applies to microbes (West et al. 2006 Nature Reviews Microbiology). We hope that the semantic debates which have wasted time in the evolutionary literature will not reoccur in the microbiology literature (West et al. 2007 J. Evol. Biol.). See also the primer on altruism.
We have demonstrated, both theoretically (West & Buckling 2003 Proc. Roy. Soc. London Ser. B), and empirically (Griffin et al. 2004 Nature; Ross-Gillespie et al. 2007 Am. Nat; Kümmerli et al. 2009 Evolution; Kümmerli et al. 2009 JEB), how kin selection influences selection on the production of public goods, such as iron scavenging siderophore molecules.
We have shown that bacteriocin production is a spiteful behaviour, whose selection is influenced by kin selection (Gardner et al. 2004 Proc. Roy. Soc.; Gardner & West 2006 Current Biology).
We have shown that cooperation by microbial symbionts can be selected for if their hosts preferentially reward partners who cooperate or punish partners that do not cooperate (West et al. 2002 Proc. Roy. Soc. London Ser. B). We have also shown that such sanctions occur in the legume-rhizobia mutualism (Kiers et al. 2003 Nature). Soybeans penalise rhizobia that fail to fix Nitrogen inside their root nodules, by decreasing Oxygen supply, which results in huge fitness costs to the rhizobia (Kiers et al. 2003 Nature).

The siderophore work is led by Ashleigh Griffin (Oxford, UK), and involves collaboration with Steve Diggle (Nottingham, UK), Angus Buckling (Oxford, UK) and Kendra Rumbaugh (Texas, USA). The theory involves collaboration with Andy Gardner. The rhizobia work involved collaboration with Toby Kiers (Amsterdam, Holland) and Ford Denison (Minnesota, USA).

Selected Relevant Publications
(click on paper titles to download a PDF)

Brown, S.P., West, S.A., Diggle, S.P. & Griffin, A.S. (2009). Social evolution in microorganisms and a Trojan horse approach to medical intervention strategies. Philosophical Transactions of The Royal Society 364, 3157-3168.
Kümmerli, R., Gardner, A., West, S.A. & Griffin, A.S. (2009) Limited dispersal, budding dispersal, and cooperation: an experimental study. Evolution 63, 939-949.
Kümmerli, R., Griffin, A.S., West, S.A., Buckling, A. & Harrison, F. (2009) Viscous medium promotes cooperation in the pathogenic bacterium Pseudomonas aeruginosa. Proceedings of the Royal Society London Series B 276, 3531-3538. {Media}
Kümmerli, R., Jiricny, N., Clarke, S., West, S.A. & Griffin, A.S. (2009) Phenotypic plasticity of a cooperative behaviour in bacteria. Journal of Evolutionary Biology 22, 589-598.
Ross-Gillespie, A., Gardner, A., Buckling, A., West, S.A. & Griffin, A.S. (2009) Density dependence and cooperation: theory and a test with bacteria. Evolution 63, 2315-2325.
Rumbaugh, K.P., Diggle, S.P., Watters, C.M., Ross-Gillespie, A., Griffin, A.S. & West, S.A. (2009). Quorum sensing and the social evolution of bacterial virulence. Current Biology 19, 341-345.
Diggle, S.P., Griffin, A.S., Campbell, G.S. & West. S.A. (2007) Cooperation and conflict in quorum-sensing bacterial populations. Nature 450, 411-414. {Media} {Making the paper} {Editorial} {Faculty of 1000}
West, S.A., Griffin, A.S. & Gardner, A. (2007) Evolutionary explanations for cooperation. Current Biology, 17, R661-R672.
West, S.A., Diggle, S.P., Buckling, A., Gardner, A. & Griffin, A.S. (2007) The social lives of microbes. Annual Review of Ecology, Evolution and Systematics, 38, 53-77.
Ross-Gillespie, A., Gardner, A., West, S.A. & Griffin, A.S. (2007) Frequency dependence and cooperation: theory and a test with bacteria. American Naturalist, 170, 331-342.
Diggle, S.P., Gardner, A., West. S.A. & Griffin, A.S. (2007) Evolutionary theory of bacterial quorum sensing: when is a signal not a signal? Philosophical Transactions of The Royal Society.
Gardner, A., West. S.A. & Griffin, A.S. (2007) Is bacterial persistence a social trait? PLOS One, 2(8), e752.
West, S.A., Griffin, A.S. & Gardner, A. (2007) Social semantics: altruism, cooperation, mutualism, strong reciprocity and group selection. Journal of Evolutionary Biology 20, 415-432. {Faculty of 1000}
West, S.A., Diggle, S.P., Buckling, A., Gardner, A. & Griffin, A.S. (2007) The social lives of microbes. Annual Review of Ecology, Evolution and Systematics, 38, 53-57.
Gardner, A. & West. S.A. (2006) Spite. Current Biology 16, R662-R664.
West, S.A., Gardner, A., & Griffin, A.S. (2006) Altruism. Current Biology 16, R482-R483.
West, S.A., Griffin, A.S., Gardner, A. & Diggle, S.P. (2006) Social evolution theory for microbes. Nature Reviews Microbiology 4, 597-607.
Gardner, A., West, S.A. & Buckling, A. (2004) Bacteriocins, spite and virulence. Proceedings of the Royal Society London Series B, 271, 1529-1535. {Science perspective} {Media}
Griffin, A.S., West, S.A. & Buckling, A. (2004) Cooperation and competition in pathogenic bacteria. Nature, 430, 1024-1027. {Nature News & Views} {Science perspective} {Media}
Kiers, E.T., Rousseau, R.A., West, S.A. & Denison, R.F. (2003) Host sanctions and the legume-rhizobia mutualism. Nature, 425, 78-81. {Media}
West, S.A. & Buckling, A. (2003) Cooperation, virulence and siderophore production in bacterial parasites. Proceedings of the Royal Society London Series B 270, 37-44.
West, S.A., Kiers, E.T., Pen, I. & Denison, R.F. (2002) Sanctions and mutualism stability: when should less beneficial mutualists be tolerated? Journal of Evolutionary Biology, 15, 830-837.
West, S.A., Kiers, E.T., Simms, E.L. & Denison, R.F. (2002) Sanctions and mutualism stability: why do rhizobia fix Nitrogen? Proceedings of the Royal Society London Series B, 269, 685-694.
Kiers, E.T., West, S.A. & Denison, R.F. (2002) Mediating mutualisms: Farm management practises and evolutionary changes in symbiont cooperation. Journal of Applied Ecology, 39, 745-754.

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