Interests - microbes

Microorganisms provide unique opportunities to study social behavior (Strassmann et al. 2000; Foster 2005; Robinson et al. 2005) . The study of cooperation has traditionally been limited by the assumption that social traits have a simple genetic basis, which can be treated as a “black box” in mechanistic terms (Robinson et al. 2005, Foster et al. 2007) . Studying microorganisms changes this and allows the black box to be opened. Their relatively simple social behaviors can be studied in the laboratory using the latest molecular and genetic techniques and, as a lab system, microbes are ideally suited to test the general theories of social evolution. For example, relatedness among cells can be manipulated to see the effects on cooperation and conflict in a wild clone (Foster et al. 2002) or lab-generated social mutant (Foster et al. 2004) . In addition, microbes are highly amenable to experimental evolution studies that follow the evolution of a social trait as it occurs. Our work so far has focused upon two microbe systems:

Slime moulds or social amoeba: For much of their life Dictyostelium discoideum amoebae are solitary, but they cooperate spectacularly to escape starvation when their bacterial prey run out. Amoebae aggregate into a differentiated multicellular “slug”, which migrates towards the soil surface and develops into a fruiting body (Foster et al. 2002) . Importantly, around a quarter of the cells die to form a stalk that holds the spore cells aloft for dispersal. This extreme altruism coupled with the ability to form groups of both related and unrelated cells makes D. discoideum an excellent model system for investigating social behavior (Strassmann et al. 2000; Foster et al. 2002; Foster et al. 2004) .

Bacterial biofilms: Bacterial biofilms, containing one or more species, adhere to almost any surface and are fundamental to the ecology and pathogenicity of bacteria (Branda et al. 2005) . Social evolution is central to biofilm formation because biofilms contain many products produced by one cell that affect other cells, such as protective matrix and feeding enzymes, for survival and nutrient acquisition. Biofilms are formed by almost all the major bacterial pathogens, including Escherichia coli, Pseudomonas aeroginosa, Klebsiella pneumoniae, Vibrio cholerae, and Streptococcus pneumoniae, and biofilms are important in both virulence and antibiotic resistance. As in D. discoideum, there are a wealth of literature and techniques available for studying the development, genetics and genomics of biofilms. By contrast, very little is known about their social evolution.

Biofilms are often assumed to require cooperation because group products are often vulnerable to exploitation by cheaters that use the products of others

without making them (Foster 2005). However, our recent work suggests that the biofilm phenotype may often be driven by conflict. In an individual-based simulation of biofilms, we found that polymer production allowed lineages of cells to rise above the other cells and suffocate them (Xavier and Foster 2007). Moreover, this behavior is often regulated by quorum sensing and our simulations suggest that the benefit of this, and whether quorum sensing causes up or down regulation of polymer production, will depend upon ecology (Nadell et al. 2008).

Our goal is to use these systems to bring novel insights to the question of how cooperation evolves in natural systems, and in particular, to investigate the genetic and genomic basis for social traits. Some broad questions include, what are the genes that code for social traits? What are the role of pleiotropy and epistasis? How does social environment affect microbial behaviors and gene expression profiles? And how do genes for social traits evolve?

Branda SS, Vik A, Friedman L, Kolter R 2005.Biofilms: the matrix revisited. Trends In Microbiology 13:20-26

Foster K.R. and Grundmann, H. 2006. Do we need to put society first? The potential for tragedy in antimicrobial resistance. PLoS Medicine, 3(2): e29 PDF

Foster KR. 2005. Hamiltonian medicine: why the social lives of pathogens matter. Science 308: 1269-1270 PDF

Foster, K.R., Parkinson, K. and Thompson, C. R. L. 2007 What can microbial genetics teach sociobiology? Trends in Genetics, 23:73-80. PDF

Foster KR., Shaulsky G, Strassmann, J. E., Queller, D. C., Thompson, C. R. L. 2004. Pleiotropy as a mechanism to stabilise cooperation. Nature 431: 693-696 PDF

Foster KR, Fortunato A, Strassmann JE, Queller DC. 2002. The costs and benefits of being a chimera. Proceedings of the Royal Society of London, Series B, 269: 2357–2362. PDF

Nadell CD, Xavier J, Levin SA, & Foster, K.R. (2008) The evolution of quorum sensing in bacterial biofilms. Plos Biology, 6: e14 PDF [Movie]

Robinson GE, Grozinger CM, Whitfield CW 2005.Sociogenomics: social life in molecular terms. Nature Review Genetics 6:257-70

Strassmann JE, Zhu Y, Queller DC 2000.Altruism and social cheating in the social amoeba Dictyostelium discoideum. Nature 408:965-967

Xavier, J.B., and Foster, K.R. 2007 Cooperation and conflict in microbial biofilms. Proceedings of the National Academy of Sciences, 104: 876-881. [PDF] [Supplementary methods + Movies]

Talk: Cooperation and conflict in D. discoideum (warning! large file) PPT