More Bang For Your Buck: Quorum-Sensing Capabilities Improve the Efficacy of Suicidal Altruism

Abstract

Within the context of evolution, an altruistic act that benefits the receiving individual at the expense of the acting individual is a puzzling phenomenon. An extreme form of altruism can be found in colicinogenic E. coli. These suicidal altruists explode, releasing colicins that kill unrelated individuals, which are not colicin resistant. By committing suicide, the altruist makes it more likely that its kin will have less competition. The benefits of this strategy rely on the number of competitors and kin nearby. If the organism explodes at an inopportune time, the suicidal act may not harm any competitors. Communication could enable organisms to act altruistically when environmental conditions suggest that that strategy would be most beneficial. Quorum sensing is a form of communication in which bacteria produce a protein and gauge the amount of that protein around them. Quorum sensing is one means by which bacteria sense the biotic factors around them and determine when to produce products, such as antibiotics, that influence competition. Suicidal altruists could use quorum sensing to determine when exploding is most beneficial, but it is challenging to study the selective forces at work in microbes. To address these challenges, we use digital evolution (a form of experimental evolution that uses self-replicating computer programs as organisms) to investigate the effects of enabling altruistic organisms to communicate via quorum sensing. We found that quorumsensing altruists killed a greater number of competitors per explosion, winning competitions against non-communicative altruists. These findings indicate that quorum sensing could increase the beneficial effect of altruism and the suite of conditions under which it will evolve.

Digital Evolution for Ecology Research: A Review

“…In collaboration with biologists, they were then able to use this system to understand how bacteria might evolve resistance to efforts to interfere with their quorum sensing (Beckmann et al, 2012). Vostinar (née Johnson) et al expanded on this research, finding that not only is the evolution of quorum sensing in Avida possible, it also increases the range of conditions in which altruism will evolve and the extent to which it is beneficial (Johnson et al, 2014). This work provided the basis for a more precisely targeted digital system that directly modeled quorum sensing in a species of bacteria (Vostinar et al, 2018).…”

The Effect of Conflicting Pressures on the Evolution of Division of Labor

“…These digital organisms execute instructions in their genome to metabolize resources in the environment, interact with neighboring organisms, and self-replicate. Digital evolution has previously been used to study topics in evolutionary biology ranging from the origin of complex features [28] , modularity [29] , leader election [30] , [ 31] , altruism [32] – [35] , and division of labor [36] – [38] . Digital evolution fills a unique niche in the study of evolutionary phenomena.…”