@article{9055, abstract = {Spontaneous formation of colonies of bacteria or flocks of birds are examples of self-organization in active living matter. Here, we demonstrate a form of self-organization from nonequilibrium driving forces in a suspension of synthetic photoactivated colloidal particles. They lead to two-dimensional "living crystals," which form, break, explode, and re-form elsewhere. The dynamic assembly results from a competition between self-propulsion of particles and an attractive interaction induced respectively by osmotic and phoretic effects and activated by light. We measured a transition from normal to giant-number fluctuations. Our experiments are quantitatively described by simple numerical simulations. We show that the existence of the living crystals is intrinsically related to the out-of-equilibrium collisions of the self-propelled particles.}, author = {Palacci, Jérémie A and Sacanna, S. and Steinberg, A. P. and Pine, D. J. and Chaikin, P. M.}, issn = {1095-9203}, journal = {Science}, keywords = {Multidisciplinary}, number = {6122}, pages = {936--940}, publisher = {American Association for the Advancement of Science }, title = {{Living crystals of light-activated colloidal surfers}}, doi = {10.1126/science.1230020}, volume = {339}, year = {2013}, } @article{9153, abstract = {Internal tide driven mixing plays a key role in sustaining the deep ocean stratification and meridional overturning circulation. Internal tides can be generated by topographic horizontal scales ranging from hundreds of meters to tens of kilometers. State of the art topographic products barely resolve scales smaller than ∼10 km in the deep ocean. On these scales abyssal hills dominate ocean floor roughness. The impact of abyssal hill roughness on internal‐tide generation is evaluated in this study. The conversion of M2 barotropic to baroclinic tidal energy is calculated based on linear wave theory both in real and spectral space using the Shuttle Radar Topography Mission SRTM30_PLUS bathymetric product at 1/120° resolution with and without the addition of synthetic abyssal hill roughness. Internal tide generation by abyssal hills integrates to 0.1 TW globally or 0.03 TW when the energy flux is empirically corrected for supercritical slope (i.e., ∼10% of the energy flux due to larger topographic scales resolved in standard products in both cases). The abyssal hill driven energy conversion is dominated by mid‐ocean ridges, where abyssal hill roughness is large. Focusing on two regions located over the Mid‐Atlantic Ridge and the East Pacific Rise, it is shown that regionally linear theory predicts an increase of the energy flux due to abyssal hills of up to 100% or 60% when an empirical correction for supercritical slopes is attempted. Therefore, abyssal hills, unresolved in state of the art topographic products, can have a strong impact on internal tide generation, especially over mid‐ocean ridges.}, author = {Melet, Angélique and Nikurashin, Maxim and Muller, Caroline J and Falahat, S. and Nycander, Jonas and Timko, Patrick G. and Arbic, Brian K. and Goff, John A.}, issn = {2169-9275}, journal = {Journal of Geophysical Research: Oceans}, number = {11}, pages = {6303--6318}, publisher = {American Geophysical Union}, title = {{Internal tide generation by abyssal hills using analytical theory}}, doi = {10.1002/2013jc009212}, volume = {118}, year = {2013}, } @article{9154, abstract = {In this study the response of tropical precipitation extremes to warming in organized convection is examined using a cloud-resolving model. Vertical shear is imposed to organize the convection into squall lines. Earlier studies show that in disorganized convection, the fractional increase of precipitation extremes is similar to that of surface water vapor, which is substantially smaller than the increase in column water vapor. It has been suggested that organized convection could lead to stronger amplifications. Regardless of the strength of the shear, amplifications of precipitation extremes in the cloud-resolving simulations are comparable to those of surface water vapor and are substantially less than increases in column water vapor. The results without shear and with critical shear, for which the squall lines are perpendicular to the shear, are surprisingly similar with a fractional rate of increase of precipitation extremes slightly smaller than that of surface water vapor. Interestingly, the dependence on shear is nonmonotonic, and stronger supercritical shear yields larger rates, close to or slightly larger than surface humidity. A scaling is used to evaluate the thermodynamic and dynamic contributions to precipitation extreme changes. To first order, they are dominated by the thermodynamic component, which has the same magnitude for all shears, close to the change in surface water vapor. The dynamic contribution plays a secondary role and tends to weaken extremes without shear and with critical shear, while it strengthens extremes with supercritical shear. These different dynamic contributions for different shears are due to different responses of convective mass fluxes in individual updrafts to warming.}, author = {Muller, Caroline J}, issn = {0894-8755}, journal = {Journal of Climate}, keywords = {Atmospheric Science}, number = {14}, pages = {5028--5043}, publisher = {American Meteorological Society}, title = {{Impact of convective organization on the response of tropical precipitation extremes to warming}}, doi = {10.1175/jcli-d-12-00655.1}, volume = {26}, year = {2013}, } @article{9167, abstract = {We introduce a self-propelled colloidal hematite docker that can be steered to a small particle cargo many times its size, dock, transport the cargo to a remote location, and then release it. The self-propulsion and docking are reversible and activated by visible light. The docker can be steered either by a weak uniform magnetic field or by nanoscale tracks in a textured substrate. The light-activated motion and docking originate from osmotic/phoretic particle transport in a concentration gradient of fuel, hydrogen peroxide, induced by the photocatalytic activity of the hematite. The docking mechanism is versatile and can be applied to various materials and shapes. The hematite dockers are simple single-component particles and are synthesized in bulk quantities. This system opens up new possibilities for designing complex micrometer-size factories as well as new biomimetic systems.}, author = {Palacci, Jérémie A and Sacanna, Stefano and Vatchinsky, Adrian and Chaikin, Paul M. and Pine, David J.}, issn = {15205126}, journal = {Journal of the American Chemical Society}, keywords = {Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis}, number = {43}, pages = {15978--15981}, publisher = {American Chemical Society}, title = {{Photoactivated colloidal dockers for cargo transportation}}, doi = {10.1021/ja406090s}, volume = {135}, year = {2013}, } @article{921, abstract = {Recent experiments have shown that spreading epithelial sheets exhibit a long-range coordination of motility forces that leads to a buildup of tension in the tissue, which may enhance cell division and the speed of wound healing. Furthermore, the edges of these epithelial sheets commonly show finger-like protrusions whereas the bulk often displays spontaneous swirls of motile cells. To explain these experimental observations, we propose a simple flocking-type mechanism, in which cells tend to align their motility forceswith their velocity. Implementing this idea in amechanical tissue simulation, the proposed model gives rise to efficient spreading and can explain the experimentally observed long-range alignment of motility forces in highly disordered patterns, as well as the buildup of tensile stress throughout the tissue. Our model also qualitatively reproduces the dependence of swirl size and swirl velocity on cell density reported in experiments and exhibits an undulation instability at the edge of the spreading tissue commonly observed in vivo. Finally, we study the dependence of colony spreading speed on important physical and biological parameters and derive simple scaling relations that show that coordination of motility forces leads to an improvement of the wound healing process for realistic tissue parameters.}, author = {Basan, Markus and Elgeti, Jens and Hannezo, Edouard B and Rappel, Wouter and Levine, Herbert}, journal = {PNAS}, number = {7}, pages = {2452 -- 2459}, publisher = {National Academy of Sciences}, title = {{Alignment of cellular motility forces with tissue flow as a mechanism for efficient wound healing}}, doi = {10.1073/pnas.1219937110}, volume = {110}, year = {2013}, } @article{9459, abstract = {Nucleosome remodelers of the DDM1/Lsh family are required for DNA methylation of transposable elements, but the reason for this is unknown. How DDM1 interacts with other methylation pathways, such as small-RNA-directed DNA methylation (RdDM), which is thought to mediate plant asymmetric methylation through DRM enzymes, is also unclear. Here, we show that most asymmetric methylation is facilitated by DDM1 and mediated by the methyltransferase CMT2 separately from RdDM. We find that heterochromatic sequences preferentially require DDM1 for DNA methylation and that this preference depends on linker histone H1. RdDM is instead inhibited by heterochromatin and absolutely requires the nucleosome remodeler DRD1. Together, DDM1 and RdDM mediate nearly all transposon methylation and collaborate to repress transposition and regulate the methylation and expression of genes. Our results indicate that DDM1 provides DNA methyltransferases access to H1-containing heterochromatin to allow stable silencing of transposable elements in cooperation with the RdDM pathway.}, author = {Zemach, Assaf and Kim, M. Yvonne and Hsieh, Ping-Hung and Coleman-Derr, Devin and Eshed-Williams, Leor and Thao, Ka and Harmer, Stacey L. and Zilberman, Daniel}, issn = {1097-4172}, journal = {Cell}, number = {1}, pages = {193--205}, publisher = {Elsevier}, title = {{The Arabidopsis nucleosome remodeler DDM1 allows DNA methyltransferases to access H1-containing heterochromatin}}, doi = {10.1016/j.cell.2013.02.033}, volume = {153}, year = {2013}, } @article{9481, abstract = {Arabidopsis thaliana endosperm, a transient tissue that nourishes the embryo, exhibits extensive localized DNA demethylation on maternally inherited chromosomes. Demethylation mediates parent-of-origin–specific (imprinted) gene expression but is apparently unnecessary for the extensive accumulation of maternally biased small RNA (sRNA) molecules detected in seeds. Endosperm DNA in the distantly related monocots rice and maize is likewise locally hypomethylated, but whether this hypomethylation is generally parent-of-origin specific is unknown. Imprinted expression of sRNA also remains uninvestigated in monocot seeds. Here, we report high-coverage sequencing of the Kitaake rice cultivar that enabled us to show that localized hypomethylation in rice endosperm occurs solely on the maternal genome, preferring regions of high DNA accessibility. Maternally expressed imprinted genes are enriched for hypomethylation at putative promoter regions and transcriptional termini and paternally expressed genes at promoters and gene bodies, mirroring our recent results in A. thaliana. However, unlike in A. thaliana, rice endosperm sRNA populations are dominated by specific strong sRNA-producing loci, and imprinted 24-nt sRNAs are expressed from both parental genomes and correlate with hypomethylation. Overlaps between imprinted sRNA loci and imprinted genes expressed from opposite alleles suggest that sRNAs may regulate genomic imprinting. Whereas sRNAs in seedling tissues primarily originate from small class II (cut-and-paste) transposable elements, those in endosperm are more uniformly derived, including sequences from other transposon classes, as well as genic and intergenic regions. Our data indicate that the endosperm exhibits a unique pattern of sRNA expression and suggest that localized hypomethylation of maternal endosperm DNA is conserved in flowering plants.}, author = {Rodrigues, Jessica A. and Ruan, Randy and Nishimura, Toshiro and Sharma, Manoj K. and Sharma, Rita and Ronald, Pamela C and Fischer, Robert L. and Zilberman, Daniel}, issn = {1091-6490}, journal = {Proceedings of the National Academy of Sciences}, keywords = {Multidisciplinary}, number = {19}, pages = {7934--7939}, publisher = {National Academy of Sciences}, title = {{Imprinted expression of genes and small RNA is associated with localized hypomethylation of the maternal genome in rice endosperm}}, doi = {10.1073/pnas.1306164110}, volume = {110}, year = {2013}, } @article{9520, abstract = {Plants undergo alternation of generation in which reproductive cells develop in the plant body ("sporophytic generation") and then differentiate into a multicellular gamete-forming "gametophytic generation." Different populations of helper cells assist in this transgenerational journey, with somatic tissues supporting early development and single nurse cells supporting gametogenesis. New data reveal a two-way relationship between early reproductive cells and their helpers involving complex epigenetic and signaling networks determining cell number and fate. Later, the egg cell plays a central role in specifying accessory cells, whereas in both gametophytes, companion cells contribute non-cell-autonomously to the epigenetic landscape of the gamete genomes.}, author = {Feng, Xiaoqi and Zilberman, Daniel and Dickinson, Hugh}, issn = {1878-1551}, journal = {Developmental Cell}, number = {3}, pages = {215--225}, publisher = {Elsevier}, title = {{A conversation across generations: Soma-germ cell crosstalk in plants}}, doi = {10.1016/j.devcel.2013.01.014}, volume = {24}, year = {2013}, } @article{9663, abstract = {Molecular dynamics simulations of small Cu nanoparticles using three different interatomic potentials at rising temperature indicate that small nanoparticles can undergo solid-solid structural transitions through a direct geometrical conversion route. The direct geometrical conversion can happen for cuboctahedral nanoparticles, which turn into an icosahedra shape: one diagonal of the square faces contracts, and the faces are folded along the diagonal to give rise to two equilateral triangles. The transition is a kinetic process that cannot be fully explained through an energetic point of view. It has low activation energy and fast reaction time in the simulations. The transition mechanism is via the transmission of shear waves initiated from the particle surface and does not involve dislocation activity.}, author = {Cheng, Bingqing and Ngan, Alfonso H. W.}, issn = {1089-7690}, journal = {The Journal of Chemical Physics}, number = {16}, publisher = {AIP Publishing}, title = {{Thermally induced solid-solid structural transition of copper nanoparticles through direct geometrical conversion}}, doi = {10.1063/1.4802025}, volume = {138}, year = {2013}, } @article{9674, abstract = {The coalescence of nano-crystals during sintering is often found to result in interesting crystalline structures such as multi-fold twins, and yet the plasticity mechanism accompanying their formation is unclear. In this work, the sintering behavior of two unsupported copper nanoparticles initially at room temperature is investigated by molecular dynamics simulations under the constant-energy ensemble. The results reveal that once the two nanoparticles are brought into contact, they often go through drastic structural changes with the inter-particle grain boundary quickly eliminated, and single- and multi-fold twinning occurs frequently in the coalesced product. Whereas the formation of single twins is found to be via the more usual mechanism of emission of Shockley partials on {1 1 1} planes, the formation of fivefold twins, however, takes place via a novel dislocation-free mechanism involving a series of shear and rigid-body rotation processes caused by elastic waves with amplitudes not corresponding to any allowable Burgers vector in the fcc lattice. Such a lattice-wave, dislocation-free twinning mechanism has never been reported before.}, author = {Cheng, Bingqing and Ngan, Alfonso H.W.}, issn = {0749-6419}, journal = {International Journal of Plasticity}, pages = {65--79}, publisher = {Elsevier}, title = {{The crystal structures of sintered copper nanoparticles: A molecular dynamics study}}, doi = {10.1016/j.ijplas.2013.01.006}, volume = {47}, year = {2013}, } @article{9676, abstract = {Despite its relevance to a range of technological applications including nanocrystalline material fabrication, the sintering mechanisms of nanoparticles have not been well understood. It has been recognized that extrapolation from understanding of macro-particle sintering is unreliable for the nano-particle size regime. In this work, the sintering behaviour of copper nanoparticles under periodic boundary conditions at different temperatures and pressures was investigated by Molecular Dynamics simulations. It was found that smaller particle sizes, higher temperature and higher external pressure facilitate densification. Through a comparison with a two-sphere model, the governing mechanisms for many nanoparticles sintered at low temperature (T⩽900K) were identified to be a variety of plasticity processes including dislocation, twinning and even amorphization at the contact neck regions, due to the presence of high stresses.}, author = {Cheng, Bingqing and Ngan, Alfonso H.W.}, issn = {0927-0256}, journal = {Computational Materials Science}, pages = {1--11}, publisher = {Elsevier}, title = {{The sintering and densification behaviour of many copper nanoparticles: A molecular dynamics study}}, doi = {10.1016/j.commatsci.2013.03.014}, volume = {74}, year = {2013}, } @article{9682, abstract = {In this work, we simulate the response of two Cu nanoparticles colliding at different approaching rates at room temperature by MD. For small nanospheres, the formation of single twins is favored at high approach rates, whereas larger nanospheres mainly deform by dislocation slip. For small nanocubes with large {100} flat surfaces, however, a dislocation-free direct geometrical conversion process that leads to five-fold twinning dominates except at highly retarded approaching rates. For larger nanocubes, single twin formation is the governing plasticity mechanism. The probability for plastic deformation by dislocation slip or twinning is attributed to the abundance of surface steps, which act as sites for dislocation nucleation.}, author = {Cheng, Bingqing and Ngan, Alfonso H.W.}, issn = {0921-5093}, journal = {Materials Science and Engineering: A}, pages = {326--334}, publisher = {Elsevier}, title = {{Crystal plasticity of Cu nanocrystals during collision}}, doi = {10.1016/j.msea.2013.07.065}, volume = {585}, year = {2013}, } @article{970, abstract = {Recently a new high-mobility Dirac material, trilayer graphene, was realized experimentally. The band structure of ABA-stacked trilayer graphene consists of a monolayer-like and a bilayer-like pair of bands. Here we study electronic properties of ABA-stacked trilayer graphene biased by a perpendicular electric field. We find that the combination of the bias and trigonal warping gives rise to a set of new Dirac points: In each valley, seven species of Dirac fermions with small masses of order of a few meV emerge. The positions and masses of the emergent Dirac fermions are tunable by bias, and one group of Dirac fermions becomes massless at a certain bias value. Therefore, in contrast to bilayer graphene, the conductivity at the neutrality point is expected to show nonmonotonic behavior, becoming of the order of a few e2/h when some Dirac masses vanish. Further, we analyze the evolution of the Landau level spectrum as a function of bias. The emergence of new Dirac points in the band structure translates into new threefold-degenerate groups of Landau levels. This leads to an anomalous quantum Hall effect, in which some quantum Hall steps have a height of 3e2/h. At an intermediate bias, the degeneracies of all Landau levels get lifted, and in this regime all quantum Hall plateaus are spaced by e2/h. Finally, we show that the pattern of Landau level crossings is very sensitive to certain band structure parameters, and can therefore provide a useful tool for determining their precise values.}, author = {Maksym Serbyn and Abanin, Dmitry A}, journal = {Physical Review B - Condensed Matter and Materials Physics}, number = {11}, publisher = {American Physical Society}, title = {{New Dirac points and multiple Landau level crossings in biased trilayer graphene}}, doi = {10.1103/PhysRevB.87.115422}, volume = {87}, year = {2013}, } @article{971, abstract = {We study the stability of the normal state in a mesoscopic NSN junction biased by a constant voltage V with respect to the formation of the superconducting order. Using the linearized time-dependent Ginzburg-Landau equation, we obtain the temperature dependence of the instability line, V inst(T), where nucleation of superconductivity takes place. For sufficiently low biases, a stationary symmetric superconducting state emerges below the instability line. For higher biases, the normal phase is destroyed by the formation of a nonstationary bimodal state with two superconducting nuclei localized near the opposite terminals. The low-temperature and large-voltage behavior of the instability line is highly sensitive to the details of the inelastic relaxation mechanism in the wire. Therefore, experimental studies of Vinst(T) in NSN junctions may be used as an effective tool to access the parameters of the inelastic relaxation in the normal state.}, author = {Maksym Serbyn and Skvortsov, Mikhail A}, journal = {Physical Review B - Condensed Matter and Materials Physics}, number = {2}, publisher = {American Physical Society}, title = {{Onset of superconductivity in a voltage-biased normal-superconducting-normal microbridge}}, doi = {10.1103/PhysRevB.87.020501}, volume = {87}, year = {2013}, } @article{972, abstract = {In topological crystalline insulators (TCIs), topology and crystal symmetry intertwine to create surface states with distinct characteristics. The breaking of crystal symmetry in TCIs is predicted to impart mass to the massless Dirac fermions. Here, we report high-resolution scanning tunneling microscopy studies of a TCI, Pb1-xSnxSe that reveal the coexistence of zero-mass Dirac fermions protected by crystal symmetry with massive Dirac fermions consistent with crystal symmetry breaking. In addition, we show two distinct regimes of the Fermi surface topology separated by a Van-Hove singularity at the Lifshitz transition point. Our work paves the way for engineering the Dirac band gap and realizing interaction-driven topological quantum phenomena in TCIs.}, author = {Okada, Yoshinori and Serbyn, Maksym and Lin, Hsin and Walkup, Daniel and Zhou, Wenwen and Dhital, Chetan and Neupane, Madhab and Xu, Suyang and Wang, Yungjui and Sankar, Raman and Chou, Fangcheng and Bansil, Arun and Hasan, Md and Wilson, Stephen and Fu, Liang and Madhavan, Vidya}, journal = {Science}, number = {6153}, pages = {1496 -- 1499}, publisher = {American Association for the Advancement of Science}, title = {{Observation of dirac node formation and mass acquisition in a topological crystalline insulator}}, doi = {10.1126/science.1239451}, volume = {341}, year = {2013}, } @article{973, abstract = {We construct a complete set of local integrals of motion that characterize the many-body localized (MBL) phase. Our approach relies on the assumption that local perturbations act locally on the eigenstates in the MBL phase, which is supported by numerical simulations of the random-field XXZ spin chain. We describe the structure of the eigenstates in the MBL phase and discuss the implications of local conservation laws for its nonequilibrium quantum dynamics. We argue that the many-body localization can be used to protect coherence in the system by suppressing relaxation between eigenstates with different local integrals of motion.}, author = {Maksym Serbyn and Papić, Zlatko and Abanin, Dmitry A}, journal = {Physical Review Letters}, number = {12}, publisher = {American Physical Society}, title = {{Local conservation laws and the structure of the many body localized states}}, doi = {10.1103/PhysRevLett.111.127201}, volume = {111}, year = {2013}, } @article{974, abstract = {We propose a possible realization of the overscreened Kondo impurity problem by a magnetic s=1/2 impurity embedded in a two-dimensional S=1 U(1) spin liquid with a Fermi surface. This problem contains an interesting interplay between non-Fermi-liquid behavior induced by a U(1) gauge field coupled to fermions and a non-Fermi-liquid fixed point in the overscreened Kondo problem. Using a large-N expansion together with an expansion in the dynamical exponent of the gauge field, we find that the coupling to the gauge field leads to weak but observable changes in the physical properties of the system at the overscreened Kondo fixed point. We discuss the extrapolation of this result to a physical case and argue that the realization of overscreened Kondo physics could lead to observations of effects due to gauge fields.}, author = {Serbyn, Maksym and Senthil, Todadri and Lee, Patrick}, journal = {Physical Review B - Condensed Matter and Materials Physics}, number = {2}, publisher = {American Physical Society}, title = {{Overscreened Kondo fixed point in S=1 spin liquid}}, doi = {10.1103/PhysRevB.88.024419}, volume = {88}, year = {2013}, } @misc{9749, abstract = {Cooperative behavior, where one individual incurs a cost to help another, is a wide spread phenomenon. Here we study direct reciprocity in the context of the alternating Prisoner's Dilemma. We consider all strategies that can be implemented by one and two-state automata. We calculate the payoff matrix of all pairwise encounters in the presence of noise. We explore deterministic selection dynamics with and without mutation. Using different error rates and payoff values, we observe convergence to a small number of distinct equilibria. Two of them are uncooperative strict Nash equilibria representing always-defect (ALLD) and Grim. The third equilibrium is mixed and represents a cooperative alliance of several strategies, dominated by a strategy which we call Forgiver. Forgiver cooperates whenever the opponent has cooperated; it defects once when the opponent has defected, but subsequently Forgiver attempts to re-establish cooperation even if the opponent has defected again. Forgiver is not an evolutionarily stable strategy, but the alliance, which it rules, is asymptotically stable. For a wide range of parameter values the most commonly observed outcome is convergence to the mixed equilibrium, dominated by Forgiver. Our results show that although forgiving might incur a short-term loss it can lead to a long-term gain. Forgiveness facilitates stable cooperation in the presence of exploitation and noise.}, author = {Zagorsky, Benjamin and Reiter, Johannes and Chatterjee, Krishnendu and Nowak, Martin}, publisher = {Public Library of Science}, title = {{Forgiver triumphs in alternating prisoner's dilemma }}, doi = {10.1371/journal.pone.0080814.s001}, year = {2013}, } @article{975, abstract = {Recent numerical work by Bardarson, Pollmann, and Moore revealed a slow, logarithmic in time, growth of the entanglement entropy for initial product states in a putative many-body localized phase. We show that this surprising phenomenon results from the dephasing due to exponentially small interaction-induced corrections to the eigenenergies of different states. For weak interactions, we find that the entanglement entropy grows as ξln (Vt/), where V is the interaction strength, and ξ is the single-particle localization length. The saturated value of the entanglement entropy at long times is determined by the participation ratios of the initial state over the eigenstates of the subsystem. Our work shows that the logarithmic entanglement growth is a universal phenomenon characteristic of the many-body localized phase in any number of spatial dimensions, and reveals a broad hierarchy of dephasing time scales present in such a phase.}, author = {Maksym Serbyn and Papić, Zlatko and Abanin, Dmitry A}, journal = {Physical Review Letters}, number = {26}, publisher = {American Physical Society}, title = {{Universal slow growth of entanglement in interacting strongly disordered systems}}, doi = {10.1103/PhysRevLett.110.260601}, volume = {110}, year = {2013}, } @misc{9751, abstract = {High relatedness among interacting individuals has generally been considered a precondition for the evolution of altruism. However, kin-selection theory also predicts the evolution of altruism when relatedness is low, as long as the cost of the altruistic act is minor compared to its benefit. Here, we demonstrate evidence for a low-cost altruistic act in bacteria. We investigated Escherichia coli responding to the attack of an obligately lytic phage by committing suicide in order to prevent parasite transmission to nearby relatives. We found that bacterial suicide provides large benefits to survivors at marginal costs to committers. The cost of suicide was low because infected cells are moribund, rapidly dying upon phage infection, such that no more opportunity for reproduction remains. As a consequence of its marginal cost, host suicide was selectively favoured even when relatedness between committers and survivors approached zero. Altogether, our findings demonstrate that low-cost suicide can evolve with ease, represents an effective host-defence strategy, and seems to be widespread among microbes. Moreover, low-cost suicide might also occur in higher organisms as exemplified by infected social insect workers leaving the colony to die in isolation.}, author = {Refardt, Dominik and Bergmiller, Tobias and Kümmerli, Rolf}, publisher = {Dryad}, title = {{Data from: Altruism can evolve when relatedness is low: evidence from bacteria committing suicide upon phage infection}}, doi = {10.5061/dryad.b1q2n}, year = {2013}, }