1. Black Queen Gene Loss in a Structured Environment The Black Queen Hypothesis (Morris et al. 2012): 1)All biological functions have a cost. If all things are equal, excluding a function causes a fitness advantage 2)Products of ‘leaky’ biological functions are unavoidably made available to the community, thus providing “public goods“. Examples of leaky functions: 1)Detoxification of an environment 2)Cross-feeding 3)‘Cheaters’ are organisms that have lost a vital leaky function, but still acquire the result of the function through the environment by completion of this function by ‘helper’ organisms 4)The fitness of cheaters and helpers is negatively frequency dependent, which means each has an advantage when rare. Therefore, they can coexist, preventing the loss of the Black Queen function in a “Tragedy of the Commons” Avida: A Platform for Digital Evolution 1)Digital organisms (Avidians) compete for processor cycles and memory in a digital environment 2)Avidians are not meant to represent biological organisms, rather entities that are able to change over time due to mutation. This implies Avida is not a simulation of life 3)Genomes are composed of instructions that, upon replication, are subject to change due to mutation, allowing evolution 1)Logical operators, such as NAND, NOR, and EQU, are mathematically calculated by instructions 2)There are an infinite number of ways to calculate logical operators 4)In the environment file, logical operators are defined as tasks, where an organism can receive a fitness benefit or cost depending on how the task is defined Black Queen Gene Loss of Toxin Removal Genes in Liquid Medium: Acknowledgements: We would like the Institute for Cyber-Enable Research at Michigan State University for granting us access to their high performance computer center and to fellow Beacon members for the assistance in trouble shooting problems. We would also like to thank ASM for providing a travel grant to attend ASM 2014 and BEACON for additional funds. We would also like to thank Neerja Hajela, Jamie Johnson, and Rafeal Martinez for maintain all lab supplies. References: Morris JJ, Lenski RE, Zinser ER. 2012. The Black Queen Hypothesis: evolution of dependencies through adaptive gene loss. mBio 3(2):e00036- 12.doi:10.1128/mBio.0003612 Nahum JR, Harding BN, Kerr B. 2011. Evolution of restraint in a structured rock-paper-scissors community. PNAS108:10831-10838 Chao L, Levin BR 1981. Structured habitats and the evolution in of anticompetitor toxins in baceria. Sci 78(10):6324-6328 Morris JJ, Papoulis SE, Lenski RE. Submitted. Coexistence of Evolving Bacteria Stabilized by a Shared “Black Queen” Function. Evolution:14-0277 Lenski RE, Ofria C, Pennock RT, Adami C. 2003. The evolutionary origin of complex features. Nature:CS790R. Devosoft. Avdia. avida.devosoft.org Spiridon E. Papoulis 124, J. Jeffrey Morris 125, Benjamin Kerr 23, Luis Zaman 123, Richard E. Lenski 12 Michigan State University 1, BEACON Center 2, University Washington 3, papoulis@msu.edu 4, jmorris@msu.edu 5 Removal of Environmental Toxin in Avida Each Avidian’s chance of death is calculated based on an individual benefit, which is dependent upon the number of detoxifying tasks completed by that individual, and a global benefit, which is dependent upon the total number of detoxifying tasks completed in its environment. Avidians experience a fitness cost when completing the logical operator NOT, which is defined as our detoxifying task in this experiment. Structured environment* mixed environment Copy Number 01230123 Conclusions: Black Queen function loss is a phenomenon that can be expanded beyond biological evolution Equilibrium depends on leakiness and individual protection of a Black Queen function in a mixed environment The same parameters have very different effects in a structured environment as compared to a mixed environment Coexistence is maintained in structured environments Black Queen negative frequency dependence avoids “The Tragedy of the Commons” while allowing the persistence of cheaters Invasion of cheaters happens faster in mixed environments Future Work: A larger parameter range to investigate how this effects structure Manipulating the environment file Investigating differences between using different logical operators in our detoxifying task Adding the ability to control the radius of proximity in structured experiments Structure will be thoroughly tested to ensure results are valid In our laboratory experiment (Morris etal., submitted), Escherichia coli had all oxidative stress genes knocked out, thus becoming vulnerable to the environmental toxin H 2 O 2. Cells regained the ability to grow after being transformed with the pBADKAT, a catalase producing plasmid. Helper organisms contained pBADKAT and produced catalase, while cheaters lacked the plasmid. Evolution experiments show coexistence was maintained between Kat+ (helper) cell and Kat- (cheater) cells over the 1200 generations (A). It was also discovered that catalase activity in the helpers actually increased during this experiment(B, gray points). During colony counts (C), helpers exhibited “sectored” colonies. These colonies originated from plasmid containing clones, and during colony growth, some cells mutated and lost the plasmid. Brown regions are plasmid containing cells while white regions are cell that lack the plasmid.This suggests that Black Queen gene loss may be possible even in a structured environment, despite the fact that structure is often though of as a protection against cheaters (Chao and Levin, 1981). Low toxicity High toxicity Toxicity and cells evenly distributed Mixed environmentStructured environment Calculating global benefit varies between mixed and structured environments. In a mixed environment, all cells in the population are assumed to be the same distance away from every other cell in the population since position is constantly changing. In a structured environment, however, position is fixed, meaning that the global benefit can only be calculated based upon the surrounding cells. Σtask= task population or task proximity proximity of cell A B C Death Rate Total tasks in the environment Number of task copies Leakiness Weakness Global BenefitIndividual Benefit Proportion of population Apparent Equilibrium High weakness, high leakinessLow weakness, low leakiness Update Effect of Structure on Coexistence of Helpers and Cheaters in Avida Proportion of subpopulations in Avida for each respective set of parameters. Simulations were initiated by injecting helpers containing 3 copies of the detoxifying task, and cheaters containing zero copies of the detoxifying task. All variables were consistent between structured and mixed simulations, except for how global benefit was calculated and how toxin flows into the environment. Proportion of population Update *parameters had no effect on structured experiments on given values