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Bet hedging

Daniel Nichol, Mark Robertson-Tessi, Peter Jeavons, Alexander R A Anderson
Non-genetic variation in phenotypes, or bet-hedging, has been observed as a driver of drug resistance in both bacterial infections and cancers. Here, we study how bet-hedging emerges in the genotype-phenotype mapping through a simple interaction model: a molecular switch. We use simple Chemical Reaction Networks to implement stochastic switches that map gene products to phenotypes and investigate the impact of structurally distinct mappings on the evolution of phenotypic heterogeneity. Bet-hedging naturally emerges within this model and is robust to evolutionary loss through mutations to both the expression of individual genes and to the network itself...
October 21, 2016: Genetics
Teresa Lenser, Kai Graeber, Özge Selin Cevik, Nezaket Adigüzel, Ali A Dönmez, Christopher Grosche, Marcel Kettermann, Sara Mayland-Quellhorst, Zsuzsanna Mérai, Setareh Mohammadin, Thu-Phuong Nguyen, Florian Rümpler, Christina Schulze, Katja Sperber, Tina Steinbrecher, Nils Wiegand, Miroslav Strnad, Ortrun Mittelsten Scheid, Stefan A Rensing, Michael Eric Schranz, Günter Theißen, Klaus Mummenhoff, Gerhard Leubner-Metzger
Understanding how plants cope with changing habitats is a timely and important topic in plant research. Phenotypic plasticity describes the capability of a genotype to produce different phenotypes when exposed to different environmental conditions. In contrast, the constant production of a set of distinct phenotypes by one genotype mediates bet hedging, a strategy that reduces the temporal variance in fitness at the expense of a lowered arithmetic mean fitness. Both phenomena are thought to represent important adaptation strategies to unstable environments...
November 2016: Plant Physiology
BingKan Xue, Stanislas Leibler
Organisms can adapt to a randomly varying environment by creating phenotypic diversity in their population, a phenomenon often referred to as "bet hedging." The favorable level of phenotypic diversity depends on the statistics of environmental variations over timescales of many generations. Could organisms gather such long-term environmental information to adjust their phenotypic diversity? We show that this process can be achieved through a simple and general learning mechanism based on a transgenerational feedback: The phenotype of the parent is progressively reinforced in the distribution of phenotypes among the offspring...
October 4, 2016: Proceedings of the National Academy of Sciences of the United States of America
Robert D Lieberthal
Long-term health insurance provides consumers with protection against persistent, negative health shocks. While the stochastic rise in medical spending growth may make some health risks harder to insure, financial assets could act as a hedge for medical spending growth risk. The purpose of this research was to determine whether such hedges exist. The results of this study were two-fold. First, the asset classes with the strongest statistical evidence as hedges were bonds, not stocks. Second, any strategy to hedge medical spending growth involved shorting assets i...
August 2016: Applied Finance and Accounting
Bram Van den Bergh, Joran E Michiels, Tom Wenseleers, Etthel M Windels, Pieterjan Vanden Boer, Donaat Kestemont, Luc De Meester, Kevin J Verstrepen, Natalie Verstraeten, Maarten Fauvart, Jan Michiels
The evolution of antibiotic resistance is a major threat to society and has been predicted to lead to 10 million casualties annually by 2050(1). Further aggravating the problem, multidrug tolerance in bacteria not only relies on the build-up of resistance mutations, but also on some cells epigenetically switching to a non-growing antibiotic-tolerant 'persister' state(2-6). Yet, despite its importance, we know little of how persistence evolves in the face of antibiotic treatment(7). Our evolution experiments in Escherichia coli demonstrate that extremely high levels of multidrug tolerance (20-100%) are achieved by single point mutations in one of several genes and readily emerge under conditions approximating clinical, once-daily dosing schemes...
2016: Nature Microbiology
Emeline Lawarée, Sébastien Gillet, Gwennaëlle Louis, Françoise Tilquin, Sophie Le Blastier, Pierre Cambier, Jean-Yves Matroule
Stress response to fluctuating environments often implies a time-consuming reprogramming of gene expression. In bacteria, the so-called bet hedging strategy, which promotes phenotypic stochasticity within a cell population, is the only fast stress response described so far(1). Here, we show that Caulobacter crescentus asymmetrical cell division allows an immediate bimodal response to a toxic metals-rich environment by allocating specific defence strategies to morphologically and functionally distinct siblings...
2016: Nature Microbiology
Christelle Leung, Sophie Breton, Bernard Angers
Different sources of epigenetic changes can increase the range of phenotypic options. Environmentally induced epigenetic changes and stochastic epimutations are, respectively, associated with phenotypic plasticity and diversifying bet-hedging. Their relative contribution is thus expected to reflect the capacity of a genotype to face distinct changes since these strategies are differentially selected according to environmental uncertainty. To test this hypothesis, we assessed the sources of epigenetic changes on clonal fish from predictable (lakes) or unpredictable (intermittent streams) environments...
August 2016: Ecology and Evolution
Sami M Kivelä, Panu Välimäki, Karl Gotthard
Deterministic seasonality can explain the evolution of alternative life history phenotypes (i.e., life history polyphenism) expressed in different generations emerging within the same year. However, the influence of stochastic variation on the expression of such life history polyphenisms in seasonal environments is insufficiently understood. Here, we use insects as a model and explore (1) the effects of stochastic variation in seasonality and (2) the life cycle on the degree of life history differentiation among the alternative developmental pathways of direct development and diapause (overwintering), and (3) the evolution of phenology...
August 2016: Ecology and Evolution
Michael Kistenmacher, J Phil Gibson
PREMISE OF THE STUDY: Bet-hedging strategies maximize long-term geometric fitness at the cost of reduced arithmetic fitness by offsetting different mortality risks. Heterocarpic systems accomplish bet-hedging through the production of two or more fruit types that vary in dormancy and dispersal ability. It is unknown whether heterocarpy also offsets predispersal mortality risks. To address this question, we investigated whether heterocarpy in Grindelia ciliata (Asteraceae) also offsets mortality risks posed by a seed predator Schinia mortua (Noctuidae) to increase plant fitness...
August 2016: American Journal of Botany
Carolina Piçarra Cassona, Fátima Pereira, Mónica Serrano, Adriano O Henriques
Genetically identical cells growing under homogeneous growth conditions often display cell-cell variation in gene expression. This variation stems from noise in gene expression and can be adaptive allowing for division of labor and bet-hedging strategies. In particular, for bacterial pathogens, the expression of phenotypes related to virulence can show cell-cell variation. Therefore, understanding virulence-related gene expression requires knowledge of gene expression patterns at the single cell level. We describe protocols for the use of fluorescence reporters for single cell analysis of gene expression in the human enteric pathogen Clostridium difficile, a strict anaerobe...
2016: Methods in Molecular Biology
David Healey, Kevin Axelrod, Jeff Gore
Genetically identical cells in microbial populations often exhibit a remarkable degree of phenotypic heterogeneity even in homogenous environments. Such heterogeneity is commonly thought to represent a bet-hedging strategy against environmental uncertainty. However, evolutionary game theory predicts that phenotypic heterogeneity may also be a response to negative frequency-dependent interactions that favor rare phenotypes over common ones. Here we provide experimental evidence for this alternative explanation in the context of the well-studied yeast GAL network...
August 3, 2016: Molecular Systems Biology
Andreas Mayer, Thierry Mora, Olivier Rivoire, Aleksandra M Walczak
Biological organisms have evolved a wide range of immune mechanisms to defend themselves against pathogens. Beyond molecular details, these mechanisms differ in how protection is acquired, processed, and passed on to subsequent generations-differences that may be essential to long-term survival. Here, we introduce a mathematical framework to compare the long-term adaptation of populations as a function of the pathogen dynamics that they experience and of the immune strategy that they adopt. We find that the two key determinants of an optimal immune strategy are the frequency and the characteristic timescale of the pathogens...
August 2, 2016: Proceedings of the National Academy of Sciences of the United States of America
Angel I Ortiz-Ceballos, Diana Pérez-Staples, Paulino Pérez-Rodríguez
Nest construction is a common form of parental care in soil organisms. However, it is unknown whether the tropical earthworm Pontoscolex corethrurus produces nests in soils with low nutritional quality habitats. Here we studied the reproductive behaviour and nest site selection of P. corethrurus, and tested the hypothesis whether P. corethrurus produces more cocoons in habitats with low nutritional quality. In bidimensional terrariums we evaluated the combined effect of the nutritional quality of habitat: (Poor Quality Habitat = PQH, Medium Quality Habitat = MQH, High Quality Habitat = HQH) and soil depth (Shallow, Intermediate, Deep) in a factorial 3(2) design...
2016: PeerJ
Sasha F Levy
Growth heterogeneity within microbial populations has been thought to increase fitness by allowing some cells to survive an unpredictable change to a harsh environment. A new study demonstrates that heterogeneity can increase fitness even in the absence of environmental changes.
May 9, 2016: Current Biology: CB
Andrés C Burgos, Daniel Polani
We consider a simple information-theoretic model of communication, in which two species of bacteria have the option of exchanging information about their environment, thereby improving their chances of survival. For this purpose, we model a system consisting of two species whose dynamics in the world are modelled by a bet-hedging strategy. It is well known that such models lend themselves to elegant information-theoretical interpretations by relating their respective long-term growth rate to the information the individual species has about its environment...
June 21, 2016: Journal of Theoretical Biology
Jorge Hidalgo, Rafael Rubio de Casas, Miguel Á Muñoz
BACKGROUND: Mixed dispersal syndromes have historically been regarded as a bet-hedging mechanism that enhances survivorship in unpredictable environments, ensuring that some propagules stay in the maternal environment while others can potentially colonize new sites. However, this entails paying the costs of both dispersal and non-dispersal. Propagules that disperse are likely to encounter unfavorable conditions, while non-dispersing propagules might form inbred populations of close relatives...
2016: BMC Evolutionary Biology
Raymond M McKie, Robin R Milhausen, Nathan J Lachowsky
Technology is playing an increasingly pervasive role among young gay men in the process of meeting potential romantic or sexual partners. We investigated challenges posed by technology related to young gay men's relationships. Focus groups (n = 9) of young gay men aged 18-24 (n = 43) were transcribed verbatim, and thematic analysis was used to identify two major themes regarding challenges to relationship development and maintenance. Subthemes include unrealistic expectations of relationships, inauthentic self-presentation online, sexual primacy over romance, increased opportunities for infidelity, and jealousy...
2017: Journal of Homosexuality
John J Gilbert
Pronounced non-genetic polymorphisms, or polyphenisms, occur in some monogonont rotifers reproducing by diploid, female parthenogenesis. In many brachionids, there is great variation in spine length. In trimorphic species of Asplanchna, females can vary in size and shape, from a small saccate morph to giant cruciform and campanulate morphs. In species that also reproduce sexually, diploid eggs can develop into two types of females. Amictic females produce diploid eggs that develop parthenogenetically into females; mictic females produce haploid eggs that develop parthenogenetically into males or, if fertilized, into resting eggs...
March 21, 2016: Biological Reviews of the Cambridge Philosophical Society
Troy Day
Epigenetic inheritance is the transmission of nongenetic material such as gene expression levels, RNA and other biomolecules from parents to offspring. There is a growing realization that such forms of inheritance can play an important role in evolution. Bacteria represent a prime example of epigenetic inheritance because a large array of cellular components is transmitted to offspring, in addition to genetic material. Interestingly, there is an extensive and growing empirical literature showing that many bacteria can form 'persister' cells that are phenotypically resistant or tolerant to antibiotics, but most of these results are not interpreted within the context of epigenetic inheritance...
April 2016: Molecular Ecology
J Christian J Ray
Phenotypic memory can predispose cells to physiological outcomes, contribute to heterogeneity in cellular populations, and allow computation of environmental features, such as nutrient gradients. In bacteria and synthetic circuits in general, memory can often be set by protein concentrations: because of the relative stability of proteins, the degradation rate is often dominated by the growth rate, and inheritance is a significant factor. Cells can then be primed to respond to events that recur with frequencies faster than the time to eliminate proteins...
August 19, 2016: ACS Synthetic Biology
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