Population-parameter sensing in the mating system of Saccharomyces cerevisiae

Sexual reproduction is a key evolutionary innovation which sets the ground for sexual selection. Sexual selection exhibits a strong dependence on the degree of competition in a mating population. The tie between active perception of competition and sexual behavior is a crucial process for intra and intersexual selection, however, its mechanisms remain largely unknown due to experimental intractability. Unicellular mating occurs under the same constraints but population and environmental parameters can be experimentally controlled and dynamic measurements of molecular and behavioral outputs can be performed. In this work, we propose that on the prototypical chemosensory mating system from Saccharomyces cerevisiae, the response magnitude generated by the presence of the complementary sex equals the probability of forming a sexual pair by chance. In chemosensory (pheromonal) mating systems, perception of competition as an indicator of mating likelihood is constrained by the following fact. Given that the most reasonable measure of the degree of competition/mating-likelihood in the population is the operational sex ratio, i.e. the fraction of individuals of a particular sex in the sexually active population (OSR in animals or theta in this work), sensory systems would need information about the abundance of individuals of both sexes, whereas the sexual response is induced by pheromones produced only by the opposite sex. Therefore, the OSR seems sensorially indistinguishable from the absolute number of potential mates, which would make mating likelihood imperceptible. By using experiments where the emitted pheromone concentration is isotropic and therefore does not depend on the distance separating mates, we manipulated population parameters and measured quantitative mating-pheromone pathway outputs to show that yeast is able to effectively sense the population sex ratio (theta) and the absolute mate number as separate cues by using a sensory disentangling mechanism. The mechanism is based on sensory input attenuation, i.e. the enzymatic degradation of the sexual pheromone produced by the opposite sex. As revealed by a simple physical model, the population displays specific sensitivities to sex ratio and cell density by modifying the time profile of pheromone concentration, with its maxima depending linearly on emitter cell density, and scaled by the inverse square root of receiver cell density. We show that in a random collision scenario the sex-ratio of the population indeed determines the likelihood of successful sexual pairing, matching the gene-expression response to sex ratio. Sensing mating likelihood allows control of mating investments, minimizing growth arrest and pathway overstimulation. Pheromone-based mate-sensing constitutes an example of a population-level fractional sensing mechanism, aided by the coupling of population-dependent signal attenuation and internal non-adaptive signal transduction. The study can be framed within the context of quantitative biology in its experimental methodology, and within (cellular) sensory systems, cell-cell communication and sexual selection theory because of its implications

Castración de bovinos. Cartilla 6

Este documento explica los aspectos más importantes para poder realizar una castración de bovinos en forma correcta y seguraThis document explains the most important aspects to be able to carry out castration of cattle correctly and safelyObjetivos de la castración. Edad para castrar -- Partes del testículo -- Métodos para castración de bovinos -- Cuidados con los animales recién castrados34 página

Toma y envío de muestras al centro de diagnósticos. Cartilla 3

Este documento enseña cómo determinar si hay fiebre o baja temperatura en el organismo del bovino para identificación oportuna de enfermedades, adicional explica como alistar el animal, alistar el termómetro, tomar la temperatura y leer el termómetroThis document teaches how to determine if there is fever or low temperature in the organism of the virus for the identification of diseases, explains how the animal, the thermometer, takes the temperature and reads the thermometerToma de la muestra -- Diagnostico de las muestras -- Proceso de ejecución para la toma de las muestras -- Recapitulación -- Evaluación final26 página

Aplicación de medicamentos vaginales y uterinos. Cartilla 10

El documento describe el aparato reproductor de la vaca, como aplicar medicamentos vía intravaginal y uterina en el momento oportuno, manejo animal y equipo y herramientas usados para aplicación de medicamentos y lavadosThe document describes the reproductive system of the cow, how to apply intravaginal and uterine medications at the right time, animal handling and equipment and tools used to apply medications and washesPor qué se requiere la aplicación de medicamentos por vía vaginal y uterina? -- Partes principales del aparato reproductor de la vaca -- Como deben ser los medicamentos que se aplican por vía vaginal y uterina -- Equipo y herramientas que se utilizan para la aplicación de medicamentos vía vaginal y uterina -- Aplicación de bolos vía intravaginal y uterina -- Aplicación de lavados o irrigaciones31 página

Castración de bovinos

Podcast de la cartilla “castración de bovinos” que describe los aspectos más importantes para poder realizar una castración de bovinos en forma correcta y segura. Se describen los objetivos de la castración, partes del testículo, métodos de castración y cuidados posteriores a la castración.Podcast of the booklet "castration of cattle" which describes the most important aspects to be able to carry out a castration of cattle in a correct and safe way. The objectives of castration, parts of the testis, methods of castration and post-castration care are described.Objetivos de la Castración: edad para castrar -- 2. Partes del testículo -- 3. Metodos para castración de bovinos: a. Castración a testículo descubierto -- b. Castración pinzas de burdizo -- c. Castración con elastrador -- 4. Cuidados con los animales recién castradosn

Sensory input attenuation allows predictive sexual response in yeast.

Animals are known to adjust their sexual behaviour depending on mate competition. Here we report similar regulation for mating behaviour in a sexual unicellular eukaryote, the budding yeast Saccharomyces cerevisiae. We demonstrate that pheromone-based communication between the two mating types, coupled to input attenuation by recipient cells, enables yeast to robustly monitor relative mate abundance (sex ratio) within a mixed population and to adjust their commitment to sexual reproduction in proportion to their estimated chances of successful mating. The mechanism of sex-ratio sensing relies on the diffusible peptidase Bar1, which is known to degrade the pheromone signal produced by mating partners. We further show that such a response to sexual competition within a population can optimize the fitness trade-off between the costs and benefits of mating response induction. Our study thus provides an adaptive explanation for the known molecular mechanism of pheromone degradation in yeast

Autonomous and Assisted Control for Synthetic Microbiology

The control of microbes and microbial consortia to achieve specific functions requires synthetic circuits that can reliably cope with internal and external perturbations. Circuits that naturally evolved to regulate biological functions are frequently robust to alterations in their parameters. As the complexity of synthetic circuits increases, synthetic biologists need to implement such robust control “by design”. This is especially true for intercellular signaling circuits for synthetic consortia, where robustness is highly desirable, but its mechanisms remain unclear. Cybergenetics, the interface between synthetic biology and control theory, offers two approaches to this challenge: external (computer-aided) and internal (autonomous) control. Here, we review natural and synthetic microbial systems with robustness, and outline experimental approaches to implement such robust control in microbial consortia through population-level cybergenetics. We propose that harnessing natural intercellular circuit topologies with robust evolved functions can help to achieve similar robust control in synthetic intercellular circuits. A “hybrid biology” approach, where robust synthetic microbes interact with natural consortia and—additionally—with external computers, could become a useful tool for health and environmental applications

Ratiometric quorum sensing governs the trade-off between bacterial vertical and horizontal antibiotic resistance propagation

International audiencePlasmid-mediated horizontal gene transfer of antibiotic resistance and virulence in pathogenic bacteria underlies a major public health issue. Understanding how, in the absence of antibiotic-mediated selection, plasmid-bearing cells avoid being outnumbered by plasmid-free cells is key to developing counterstrategies. Here, we quantified the induction of the plasmidial sex pheromone pathway of Enterococcus faecalis to show that the integration of the stimulatory (mate-sensing) and inhibitory (self-sensing) signaling modules from the pCF10 conjugative plasmid provides a precise measure of the recipient-to-donor ratio, agnostic to variations in population size. Such ratiometric control of conjugation favors vertical plasmid transfer under low mating likelihood and allows activation of conjugation functions only under high mating likelihood. We further show that this strategy constitutes a cost-effective investment into mating effort because overstimulation produces unproductive self-aggregation and growth rate reduction. A mathematical model suggests that ratiometric control of conjugation increases plasmid fitness and predicts a robust long-term, stable coexistence of donors and recipients. Our results demonstrate how population-level parameters can control transfer of antibiotic resistance in bacteria, opening the door for biotic control strategies

The Promise of Optogenetics for Bioproduction: Dynamic Control Strategies and Scale-Up Instruments

International audienceProgress in metabolic engineering and synthetic and systems biology has made bioproduction an increasingly attractive and competitive strategy for synthesizing biomolecules, recombinant proteins and biofuels from renewable feedstocks. Yet, due to poor productivity, it remains difficult to make a bioproduction process economically viable at large scale. Achieving dynamic control of cellular processes could lead to even better yields by balancing the two characteristic phases of bioproduction, namely, growth versus production, which lie at the heart of a trade-off that substantially impacts productivity. The versatility and controllability offered by light will be a key element in attaining the level of control desired. The popularity of light-mediated control is increasing, with an expanding repertoire of optogenetic systems for novel applications, and many optogenetic devices have been designed to test optogenetic strains at various culture scales for bioproduction objectives. In this review, we aim to highlight the most important advances in this direction. We discuss how optogenetics is currently applied to control metabolism in the context of bioproduction, describe the optogenetic instruments and devices used at the laboratory scale for strain development, and explore how current industrial-scale bioproduction processes could be adapted for optogenetics or could benefit from existing photobioreactor designs. We then draw attention to the steps that must be undertaken to further optimize the control of biological systems in order to take full advantage of the potential offered by microbial factories