Smith (2001) then demonstrated that allowing plasmids to carry the gene producing the public good could lead to the “tragedy” being averted, and cooperation maintained in the face of cheats-as the cheats would become infected with the plasmid and therefore with the cooperative gene. Smith's study first captured the familiar social dynamics of chromosomally determined cooperators and defectors, illustrating that a population of individuals that produced a public good could easily be invaded by individuals that did not produce it, resulting in the breakdown of the public good ( Smith 2001), an outcome known as “the tragedy of the commons” ( Hardin 1968 Rankin et al. This result seems to confirm a previous theoretical study ( Smith 2001), which suggested that horizontal transfer is an important mechanism for the maintenance of cooperation in microbes. Plasmids may be seen as parasitic DNA and changes to the bacterial and plasmid chromosome to facilitate a reduction in the deleterious effect of the plasmid may be expected and observed over time ( Bouma and Lenski 1988 Modi and Adams 1991), although it is also well-known that plasmids also carry benefits to their host ( Simonsen 1991 Rankin et al., in press).Ī recent study, which looked into the set of proteins expressed in 22 Escherichia and Shigella genomes, found that secreted proteins were overrepresented on mobile elements ( Nogueira et al. Plasmids can be inherited vertically, during cell division, or can be transmitted horizontally between different bacterial lineages. A bacterial plasmid is a species of nonessential extrachromosomal DNA that replicates autonomously as a moderately stable component of the cell's genome ( Novick 1987). 2006 Xavier and Foster 2007).īacterial genomes often contain mobile genetic elements such as conjugative plasmids or lysogenic phages ( Frost et al. 2007) or biofilm formation ( Brockhurst et al. Such public goods can be seen in a wide range of bacterial products such as siderophore production ( Griffin et al. As such, the production of public goods is prone to the invasion of nonproducers, who gain the benefit of the public good without paying the cost of production ( West et al. The production of public goods, which are costly to the producer while benefiting other members of the population, is possibly the most common form of social behavior in microbes ( West et al. Microorganisms are now known to display all of the hallmarks of a complex and coordinated social life ( Crespi 2001 West et al.
We discuss our results in the light of recent bioinformatic evidence that cooperative genes are overrepresented on mobile elements. Our results suggest that although plasmid carriage of cooperative genes can provide a transient defense against defection in structured environments, plasmid and chromosomal defection remain the only stable strategies in an unstructured environment.
#Otto matic cheats code
Here we introduce a second plasmid that does not code for cooperation and show that the social dilemma repeats itself at the plasmid level in both within-patch and metapopulation scenarios, and under various scenarios of plasmid incompatibility. When a gene for cooperative behavior exists on a plasmid, cheaters can be forced to cooperate by infection with this plasmid, rescuing cooperation in a population in which mutation or migration has allowed cheaters to arise.
Bacterial genomes often contain mobile genetic elements such as plasmids. Bacteria frequently exhibit cooperative behaviors but cooperative strains are vulnerable to invasion by cheater strains that reap the benefits of cooperation but do not perform the cooperative behavior themselves.
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