scholarly journals Memory shapes microbial populations

2021 ◽  
Vol 17 (10) ◽  
pp. e1009431
Author(s):  
Chaitanya S. Gokhale ◽  
Stefano Giaimo ◽  
Philippe Remigi
Keyword(s):  
Environmental Changes ◽  
Population Level ◽  
Stochastic Simulations ◽  
Bacterial Survival ◽  
Deterministic Modelling ◽  
Lag Times ◽  
Living Organisms ◽  
Binary Switching ◽  
Available Information ◽  
Phenotypic State

Correct decision making is fundamental for all living organisms to thrive under environmental changes. The patterns of environmental variation and the quality of available information define the most favourable strategy among multiple options, from randomly adopting a phenotypic state to sensing and reacting to environmental cues. Cellular memory—the ability to track and condition the time to switch to a different phenotypic state—can help withstand environmental fluctuations. How does memory manifest itself in unicellular organisms? We describe the population-wide consequences of phenotypic memory in microbes through a combination of deterministic modelling and stochastic simulations. Moving beyond binary switching models, our work highlights the need to consider a broader range of switching behaviours when describing microbial adaptive strategies. We show that memory in individual cells generates patterns at the population level coherent with overshoots and non-exponential lag times distributions experimentally observed in phenotypically heterogeneous populations. We emphasise the implications of our work in understanding antibiotic tolerance and, in general, bacterial survival under fluctuating environments.

scholarly journals Memory shapes microbial populations

2020 ◽  
Author(s):  
Chaitanya S. Gokhale ◽  
Stefano Giaimo ◽  
Philippe Remigi
Keyword(s):  
Environmental Changes ◽  
Stochastic Simulations ◽  
Microbial Populations ◽  
Temporal Correlations ◽  
Deterministic Modelling ◽  
General Survival ◽  
Living Organisms ◽  
Binary Switching ◽  
Multicellular Organisms ◽  
Available Information

AbstractCorrect decision making is fundamental for all living organisms to thrive under environmental changes. The patterns of environmental variation and the quality of available information define the most favourable strategy among multiple options, including sensing and reacting to environmental cues or randomly adopting a phenotypic state. Memory – a phenomenon often associated with, but not restricted to, higher multicellular organisms – can help when temporal correlations exist. How does memory manifest itself in unicellular organisms? Through a combination of deterministic modelling and stochastic simulations, we describe the population-wide fitness consequences of phenotypic memory in microbial populations. Moving beyond binary switching models, our work highlights the need to consider a broader range of switching behaviours when describing microbial adaptive strategies. We show that multiple cellular states capture the empirical observations of lag time distributions, overshoots, and ultimately the phenomenon of phenotypic heterogeneity. We emphasise the implications of our work in understanding antibiotic tolerance, and, in general, survival under fluctuating environments.

scholarly journals Reef development and Sea level changes drive Acanthaster Population Expansion in the Indo-Pacific region

2020 ◽  
Author(s):  
P.C. Pretorius ◽  
T.B. Hoareau
Keyword(s):  
Population Size ◽  
Sea Level ◽  
Environmental Changes ◽  
Sequence Data ◽  
Demographic History ◽  
Population Expansion ◽  
Population Level ◽  
Sea Level Changes ◽  
Reef Development ◽  
Curve Fitting Method

AbstractMolecular clock calibration is central in population genetics as it provides an accurate inference of demographic history, whereby helping with the identification of driving factors of population changes in an ecosystem. This is particularly important for coral reef species that are seriously threatened globally and in need of conservation. Biogeographic events and fossils are the main source of calibration, but these are known to overestimate timing and parameters at population level, which leads to a disconnection between environmental changes and inferred reconstructions. Here, we propose the Last Glacial Maximum (LGM) calibration that is based on the assumptions that reef species went through a bottleneck during the LGM, which was followed by an early yet marginal increase in population size. We validated the LGM calibration using simulations and genetic inferences based on Extended Bayesian Skyline Plots. Applying it to mitochondrial sequence data of crown-of-thorns starfish Acanthaster spp., we obtained mutation rates that were higher than phylogenetically based calibrations and varied among populations. The timing of the greatest increase in population size differed slightly among populations, but all started between 10 and 20 kya. Using a curve-fitting method, we showed that Acanthaster populations were more influenced by sea-level changes in the Indian Ocean and by reef development in the Pacific Ocean. Our results illustrate that the LGM calibration is robust and can probably provide accurate demographic inferences in many reef species. Application of this calibration has the potential to help identify population drivers that are central for the conservation and management of these threatened ecosystems.

scholarly journals What works to promote walking at the population level? A systematic review

2018 ◽  
Vol 52 (12) ◽  
pp. 807-812 ◽  
Author(s):  
Charlie Foster ◽  
Paul Kelly ◽  
Hamish A B Reid ◽  
Nia Roberts ◽  
Elaine M Murtagh ◽  
...  
Keyword(s):  
Systematic Review ◽  
Mass Media ◽  
English Language ◽  
Environmental Changes ◽  
Controlled Trial ◽  
Population Level ◽  
Eligibility Criteria ◽  
Community Initiatives ◽  
School Based ◽  
Randomised Controlled

ObjectiveInterventions to promote walking have focused on individual or group-based approaches, often via the randomised controlled trial design. Walking can also be promoted using population health approaches. We systematically reviewed the effectiveness of population approaches to promote walking among individuals and populations.DesignA systematic review.Data sources10 electronic databases searched from January 1990 to March 2017.Eligibility criteriaEligibility criteria include pre-experimental and postexperimental studies of the effects of population interventions to change walking, and the effects must have been compared with a ‘no intervention’, or comparison group/area/population, or variation in exposure; duration of ≥12 months of follow up; participants in free-living populations; and English-language articles.Results12 studies were identified from mostly urban high-income countries (one focusing on using tax, incentivising the loss of parking spaces; and one using policy only, permitting off-leash dogs in city parks). Five studies used mass media with either environment (n=2) or community (n=3) approaches. Four studies used environmental changes that were combined with policies. One study had scaled up school-based approaches to promote safe routes to schools. We found mass media, community initiatives and environmental change approaches increased walking (range from 9 to 75 min/week).

scholarly journals The effect of sexual selection on adaptation and extinction under increasing temperatures

2018 ◽  
Vol 285 (1877) ◽  
pp. 20180303 ◽  
Author(s):  
Jonathan M. Parrett ◽  
Robert J. Knell
Keyword(s):  
Sexual Selection ◽  
Environmental Changes ◽  
Population Level ◽  
Offspring Survival ◽  
Positive Effects ◽  
Fitness Consequences ◽  
Indian Meal ◽  
Mating Opportunities ◽  
Entire Experiment ◽  
Positive Effect

Strong sexual selection has been reported to both enhance and hinder the adaptive capacity and persistence of populations when exposed to novel environments. Consequently, how sexual selection influences population adaption and persistence under stress remains widely debated. Here, we present two empirical investigations of the fitness consequences of sexual selection on populations of the Indian meal moth, Plodia interpunctella, exposed to stable or gradually increasing temperatures. When faced with increasing temperatures, strong sexual selection was associated with both increased fecundity and offspring survival compared with populations experiencing weak sexual selection, suggesting sexual selection acts to drive adaptive evolution by favouring beneficial alleles. Strong sexual selection did not, however, delay extinction when the temperature became excessively high. By manipulating individuals' mating opportunities during fitness assays, we were able to assess the effect of multiple mating independently from the effect of population-level sexual selection, and found that polyandry has a positive effect on both fecundity and offspring survival under increasing temperatures in those populations evolving with weak sexual selection. Within stable temperatures, there were some benefits from strong sexual selection but these were not consistent across the entire experiment, possibly reflecting changing costs and benefits of sexual selection under stabilizing and directional selection. These results indicate that sexual selection can provide a buffer against climate change and increase adaptation rates within a continuously changing environment. These positive effects of sexual selection may, however, be too small to protect populations and delay extinction when environmental changes are relatively rapid.

Risk factor intervention at the population level

ESC CardioMed ◽  
2018 ◽  
pp. 873-882
Author(s):  
Eva Prescott ◽  
Torben Jørgensen ◽  
Maja-Lisa Løchen ◽  
Jonathan Pearson-Stuttard ◽  
Simon Capewell
Keyword(s):  
Cardiovascular Health ◽  
Environmental Changes ◽  
Population Level ◽  
Population Based ◽  
Entire Life ◽  
Individual Level ◽  
Convenience Stores ◽  
Disability Adjusted Life ◽  
Life Years ◽  
Unhealthy Diet

Great health benefits can be achieved if preventive efforts are focused on whole populations rather than mainly on high-risk individuals. Tobacco smoking, unhealthy diet, physical inactivity, alcohol abuse, and air pollution are responsible for a large proportion of global deaths and loss of disability-adjusted life years and there are documented effects of interventions at the population level on all of these factors. Population-based strategies include fiscal measures (i.e. taxation and subsidies), international, national, and regional policy regulations and legislation (e.g. smoke-free policies, rules for marketing, food production), and environmental changes (e.g. access to recreational areas, convenience stores), and have the advantages of addressing cardiovascular health over the entire life course, reducing health inequalities and saving costs when compared to individual-level interventions.

Neural Autopoiesis: Organizing Self-Boundaries by Stimulus Avoidance in Biological and Artificial Neural Networks

2020 ◽  
Vol 26 (1) ◽  
pp. 130-151 ◽  
Author(s):  
Atsushi Masumori ◽  
Lana Sinapayen ◽  
Norihiro Maruyama ◽  
Takeshi Mita ◽  
Douglas Bakkum ◽  
...  
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Environmental Changes ◽  
Spike Timing ◽  
Spiking Neural Networks ◽  
Cultured Neurons ◽  
Autonomous Regulation ◽  
Artificial Neural ◽  
Living Organisms ◽  
External Stimuli

Living organisms must actively maintain themselves in order to continue existing. Autopoiesis is a key concept in the study of living organisms, where the boundaries of the organism are not static but dynamically regulated by the system itself. To study the autonomous regulation of a self-boundary, we focus on neural homeodynamic responses to environmental changes using both biological and artificial neural networks. Previous studies showed that embodied cultured neural networks and spiking neural networks with spike-timing dependent plasticity (STDP) learn an action as they avoid stimulation from outside. In this article, as a result of our experiments using embodied cultured neurons, we find that there is also a second property allowing the network to avoid stimulation: If the agent cannot learn an action to avoid the external stimuli, it tends to decrease the stimulus-evoked spikes, as if to ignore the uncontrollable input. We also show such a behavior is reproduced by spiking neural networks with asymmetric STDP. We consider that these properties are to be regarded as autonomous regulation of self and nonself for the network, in which a controllable neuron is regarded as self, and an uncontrollable neuron is regarded as nonself. Finally, we introduce neural autopoiesis by proposing the principle of stimulus avoidance.

Managing Smokefree Momentum: Young RYO Smokers’ Responses to Tobacco Endgame Strategies

2020 ◽  
Vol 40 (2) ◽  
pp. 250-265
Author(s):  
Shelagh Ferguson ◽  
Jan Brace-Govan ◽  
Janet Hoek ◽  
Matthew Mulconroy
Keyword(s):  
Public Policy ◽  
Environmental Changes ◽  
Management Strategies ◽  
Population Level ◽  
Sense Making ◽  
Consumer Resistance ◽  
Policy Initiatives ◽  
The Social ◽  
Depth Interviews ◽  
Tobacco Endgame

As more countries set smoking endgame goals and introduce measures to denormalize smoking, smokers’ experience of stigma may intensify and require new management strategies. Probing the tension between environmental changes that support population-level behaviour change and individuals’ sense making, which occurs at a micro, everyday level, provides unique insights into reactance, agency and stigma. Using a Foucauldian informed approach, we analyze how young RYO (roll-your-own tobacco) smokers internalize neoliberal marketplace economic norms and create positions of resistance. Experience-based videographies and in-depth interviews with 15 New Zealand young adults aged 20-30 illustrate how participants resist stigma and the social disapproval they experience. This analysis identifies how smoking denormalization affects practices and pleasures, and generates four discernible positions of resistance: Socialized, Comfort, Status and Pleasure Orientated Resistances. These highlight intersections between policy initiatives and consumer resistance, offering new insights relevant to public policy.

The Effect of NaCl on Survival of Shigella flexneri in Broth as Affected by Temperature and pH†‡

2002 ◽  
Vol 65 (5) ◽  
pp. 774-779 ◽  
Author(s):  
LAURA L. ZAIKA
Keyword(s):  
Shigella Flexneri ◽  
Foodborne Pathogen ◽  
Brain Heart Infusion ◽  
Major Effect ◽  
Plate Count ◽  
Bacterial Survival ◽  
Two Phase ◽  
Bacterial Populations ◽  
Lag Times ◽  
D Values

Shigella, a major foodborne pathogen, survives well in salt-containing environments. However, systematic data are scarce. We studied the behavior of Shigella flexneri 5348 in brain heart infusion broth (pH 4 to 6) containing 0.5 to 8% NaCl. Stationary-phase cells were inoculated into sterile media at initial concentrations of 6 to 7 log10 CFU/ml and incubated at 12 to 37°C. Bacterial population sizes were determined periodically by plate counts. Survivor curves were derived from plate count data by using a two-phase linear model to determine lag times and slopes of the curves, from which decimal reduction times (D-values) and times to a 4-log10 inactivation (T4D) were calculated. In media of pH 6, the bacteria grew in the presence of ≤6% NaCl at 19 and 37°C and in the presence of ≤7% NaCl at 28°C. In media of pH 5, growth was observed in the presence of ≤2, ≤4, ≤4, and 0.5% NaCl at 37, 28, 19, and 12°C, respectively. Growth did not occur and bacterial populations gradually declined in media of pH 4. While NaCl had a major effect on growth, bacterial survival was affected to a lesser extent. Lag times decreased with increasing NaCl levels; however, the effect on D-values and T4D values was less pronounced. The average T4D values for media of pH 4 containing 0.5 to 6% NaCl were 4, 13, 23, and 61 days at 37, 28, 19, and 12°C, respectively. These results show that S. flexneri is salt tolerant and suggest that salty foods may serve as vehicles for infection with this bacterium.

scholarly journals Enzymes Involved in the Biosynthesis of Arginine from Ornithine in Maritime Pine (Pinus pinaster Ait.)

Plants ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1271
Author(s):  
José Alberto Urbano-Gámez ◽  
Jorge El-Azaz ◽  
Concepción Ávila ◽  
Fernando N. de la Torre ◽  
Francisco M. Cánovas
Keyword(s):  
Pinus Pinaster ◽  
Storage Proteins ◽  
Maritime Pine ◽  
Molecular Characteristics ◽  
Nitrogenous Compounds ◽  
Wide Range ◽  
Pinus Pinaster Ait ◽  
Living Organisms ◽  
Available Information ◽  
Regulatory Properties

The amino acids arginine and ornithine are the precursors of a wide range of nitrogenous compounds in all living organisms. The metabolic conversion of ornithine into arginine is catalyzed by the sequential activities of the enzymes ornithine transcarbamylase (OTC), argininosuccinate synthetase (ASSY) and argininosuccinate lyase (ASL). Because of their roles in the urea cycle, these enzymes have been purified and extensively studied in a variety of animal models. However, the available information about their molecular characteristics, kinetic and regulatory properties is relatively limited in plants. In conifers, arginine plays a crucial role as a main constituent of N-rich storage proteins in seeds and serves as the main source of nitrogen for the germinating embryo. In this work, recombinant PpOTC, PpASSY and PpASL enzymes from maritime pine (Pinus pinaster Ait.) were produced in Escherichia coli to enable study of their molecular and kinetics properties. The results reported here provide a molecular basis for the regulation of arginine and ornithine metabolism at the enzymatic level, suggesting that the reaction catalyzed by OTC is a regulatory target in the homeostasis of ornithine pools that can be either used for the biosynthesis of arginine in plastids or other nitrogenous compounds in the cytosol.

scholarly journals Genomics of adaptation and speciation in cichlid fishes: recent advances and analyses in African and Neotropical lineages

2012 ◽  
Vol 367 (1587) ◽  
pp. 385-394 ◽  
Author(s):  
Shaohua Fan ◽  
Kathryn R. Elmer ◽  
Axel Meyer
Keyword(s):  
Expressed Sequence Tag ◽  
Population Level ◽  
Genomic Diversity ◽  
Cichlid Fishes ◽  
Exciting Opportunity ◽  
Phenotypic Diversification ◽  
Genetics Of Adaptation ◽  
Available Information ◽  
African Cichlids ◽  
Expressed Sequence

Cichlid fishes are remarkably phenotypically diverse and species-rich. Therefore, they provide an exciting opportunity for the study of the genetics of adaptation and speciation by natural and sexual selection. Here, we review advances in the genomics and transcriptomics of cichlids, particularly regarding ecologically relevant differences in body shape, trophic apparatus, coloration and patterning, and sex determination. Research conducted so far has focused almost exclusively on African cichlids. To analyse genomic diversity and selection in a Neotropical radiation, we conducted a comparative transcriptomic analysis between sympatric, ecologically divergent crater-lake Midas cichlids (Lake Xiloá Amphilophus amarillo and Amphilophus sagittae ). We pyrosequenced (Roche 454) expressed sequence tag (EST) libraries and generated more than 178 000 000 ESTs and identified nine ESTs under positive selection between these sister species ( K a/ K s > 1). None of these ESTs were found to be under selection in African cichlids. Of 11 candidate genes for ecomorphological differentiation in African cichlids, none showed signs of selection between A. amarillo and A. sagittae . Although more population-level studies are now needed to thoroughly document patterns of divergence during speciation of cichlids, available information so far suggests that adaptive phenotypic diversification in Neotropical and African cichlids may be evolving through non-parallel genetic bases.

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