scholarly journals Migration alters oscillatory dynamics and promotes survival in connected bacterial populations

2017 ◽  
Author(s):  
Shreyas Gokhale ◽  
Arolyn Conwill ◽  
Tanvi Ranjan ◽  
Jeff Gore
Keyword(s):  
Population Dynamics ◽  
Phase Synchronization ◽  
Mechanistic Model ◽  
Vital Role ◽  
Bacterial Populations ◽  
Migration Rates ◽  
Oscillatory Dynamics ◽  
Probability Of Survival ◽  
High Migration ◽  
Connected Populations

AbstractMigration influences population dynamics on networks, thereby playing a vital role in scenarios ranging from species extinction to epidemic propagation. While low migration rates prevent local populations from becoming extinct, high migration rates enhance the risk of global extinction by synchronizing the dynamics of connected populations. Here, we investigate this trade-off using two mutualistic strains of E. coli that exhibit population oscillations when co-cultured. In experiments, as well as in simulations using a mechanistic model, we observe that high migration rates lead to in-phase synchronization whereas intermediate migration rates perturb the oscillations and change their period. Further, our simulations predict, and experiments show, that connected populations subjected to more challenging antibiotic concentrations have the highest probability of survival at intermediate migration rates. Finally, we identify altered population dynamics, rather than recolonization, as the primary cause of extended survival.

scholarly journals Death and population dynamics affect mutation rate estimates and evolvability under stress in bacteria

2017 ◽  
Author(s):  
Antoine Frénoy ◽  
Sebastian Bonhoeffer
Keyword(s):  
Population Dynamics ◽  
Mutation Rate ◽  
Death Rate ◽  
Mutation Rates ◽  
Resistance Mutations ◽  
Bacterial Populations ◽  
Plasmid Segregation ◽  
Genome Wide ◽  
Response To Stress ◽  
Induced Mutagenesis

AbstractThe stress-induced mutagenesis paradigm postulates that in response to stress, bacteria increase their genome-wide mutation rate, in turn increasing the chances that a descendant is able to withstand the stress. This has implications for antibiotic treatment: exposure to sub-inhibitory doses of antibiotics has been reported to increase bacterial mutation rates, and thus probably the rate at which resistance mutations appear and lead to treatment failure.Measuring mutation rates under stress, however, is problematic, because existing methods assume there is no death. Yet sub-inhibitory stress levels may induce a substantial death rate. Death events need to be compensated by extra replication to reach a given population size, thus giving more opportunities to acquire mutations. We show that ignoring death leads to a systematic overestimation of mutation rates under stress.We developed a system using plasmid segregation to measure death and growth rates simultaneously in bacterial populations. We use it to replicate classical experiments reporting antibiotic-induced mutagenesis. We found that a substantial death rate occurs at the tested sub-inhibitory concentrations, and taking this death into account lowers and sometimes removes the signal for stress-induced mutagenesis. Moreover even when antibiotics increase mutation rate, sub-inhibitory treatments do not increase genetic diversity and evolvability, again because of effects of the antibiotics on population dynamics.Beside showing that population dynamic is a crucial but neglected parameter affecting evolvability, we provide better experimental and computational tools to study evolvability under stress, leading to a re-assessment of the magnitude and significance of the stress-induced mutagenesis paradigm.

scholarly journals Modelling the impact of climate change on the distribution and abundance of tsetse in Northern Zimbabwe

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Joshua Longbottom ◽  
Cyril Caminade ◽  
Harry S. Gibson ◽  
Daniel J. Weiss ◽  
Steve Torr ◽  
...  
Keyword(s):  
Climate Change ◽  
Population Dynamics ◽  
Spatial Resolution ◽  
Air Temperature ◽  
Mechanistic Model ◽  
Tsetse Flies ◽  
Weather Station ◽  
Catch Data ◽  
Tsetse Population ◽  
The Impact

Abstract Background Climate change is predicted to impact the transmission dynamics of vector-borne diseases. Tsetse flies (Glossina) transmit species of Trypanosoma that cause human and animal African trypanosomiasis. A previous modelling study showed that temperature increases between 1990 and 2017 can explain the observed decline in abundance of tsetse at a single site in the Mana Pools National Park of Zimbabwe. Here, we apply a mechanistic model of tsetse population dynamics to predict how increases in temperature may have changed the distribution and relative abundance of Glossina pallidipes across northern Zimbabwe. Methods Local weather station temperature measurements were previously used to fit the mechanistic model to longitudinal G. pallidipes catch data. To extend the use of the model, we converted MODIS land surface temperature to air temperature, compared the converted temperatures with available weather station data to confirm they aligned, and then re-fitted the mechanistic model using G. pallidipes catch data and air temperature estimates. We projected this fitted model across northern Zimbabwe, using simulations at a 1 km × 1 km spatial resolution, between 2000 to 2016. Results We produced estimates of relative changes in G. pallidipes mortality, larviposition, emergence rates and abundance, for northern Zimbabwe. Our model predicts decreasing tsetse populations within low elevation areas in response to increasing temperature trends during 2000–2016. Conversely, we show that high elevation areas (> 1000 m above sea level), previously considered too cold to sustain tsetse, may now be climatically suitable. Conclusions To our knowledge, the results of this research represent the first regional-scale assessment of temperature related tsetse population dynamics, and the first high spatial-resolution estimates of this metric for northern Zimbabwe. Our results suggest that tsetse abundance may have declined across much of the Zambezi Valley in response to changing climatic conditions during the study period. Future research including empirical studies is planned to improve model accuracy and validate predictions for other field sites in Zimbabwe.

Modelling the rate of successful search of red foxes during population control

2019 ◽  
Vol 46 (4) ◽  
pp. 285 ◽  
Author(s):  
Tom A. Porteus ◽  
Jonathan C. Reynolds ◽  
Murdoch K. McAllister
Keyword(s):  
Population Dynamics ◽  
Survey Methods ◽  
Mechanistic Model ◽  
Local Population ◽  
Parallel Applications ◽  
Sources Of Information ◽  
Absolute Abundance ◽  
Red Foxes ◽  
Informative Prior ◽  
Successful Search

Context Relative abundance indices of wildlife can be scaled to give estimates of absolute abundance. Choice of scaling parameter depends on the data available and assumptions made about the relationship between the index and absolute abundance. Predation-mechanics theory suggests that a parameterisation involving the rate of successful search, s, will be useful where the area searched is unknown. An example arises during fox culling on shooting estates in Britain, where detection and cull data from gamekeepers using a spotlight and rifle are available, and can potentially be used to understand the population dynamics of the local population. Aims We aimed to develop an informative prior for s for use within a Bayesian framework to fit a fox population-dynamics model to detection data. Methods We developed a mechanistic model with a rate of successful search parameter for the gamekeeper–fox system. We established a mechanistic prior for s, using Monte Carlo simulation to combine relevant information on its component factors (detection probability, observer field of view and speed of travel). We obtained empirical estimates of s from a distance-sampling study of fox populations using similar survey methods, and used these as data in a Bayesian model to develop a mechanistic–empirical prior. We then applied this informative prior within a state–space model to estimate fox density from fox-detection rate on four estates. Key results The mechanistic–empirical prior for the rate of successful search was lognormally distributed with a median of 2.01 km2 h–1 (CV = 0.56). Underlying assumptions of the parameterisation were met. Local fox-density estimates obtained using informative priors closely reflected regional density. Conclusions A mechanistic understanding of the search process leading to fox detections by gamekeepers, and the use of Bayesian models, allowed the use of diverse sources of information to develop an informative prior for s that was useful in estimating fox density from detection data. Implications Careful use of prior knowledge within a Bayesian modelling framework can reduce uncertainty in population estimates derived from index data, and lead to improved management decisions. The mechanistic approach we have used will have parallel applications in many other contexts.

scholarly journals Hamiltonian model of capture into mean motion resonance

2010 ◽  
Vol 6 (S276) ◽  
pp. 300-303 ◽  
Author(s):  
Alexander J. Mustill ◽  
Mark C. Wyatt
Keyword(s):  
Extrasolar Planets ◽  
Kuiper Belt ◽  
Mean Motion Resonances ◽  
Migration Rates ◽  
Mean Motion ◽  
Hamiltonian Model ◽  
Planet Migration ◽  
High Migration ◽  
Relative Migration ◽  
Probability Of Capture

AbstractMean motion resonances are a common feature of both our own Solar System and of extrasolar planetary systems. Bodies can be trapped in resonance when their orbital semi-major axes change, for instance when they migrate through a protoplanetary disc. We use a Hamiltonian model to thoroughly investigate the capture behaviour for first and second order resonances. Using this method, all resonances of the same order can be described by one equation, with applications to specific resonances by appropriate scaling. We focus on the limit where one body is a massless test particle and the other a massive planet. We quantify how the the probability of capture into a resonance depends on the relative migration rate of the planet and particle, and the particle's eccentricity. Resonant capture fails for high migration rates, and has decreasing probability for higher eccentricities, although for certain migration rates, capture probability peaks at a finite eccentricity. We also calculate libration amplitudes and the offset of the libration centres for captured particles, and the change in eccentricity if capture does not occur. Libration amplitudes are higher for larger initial eccentricity. The model allows for a complete description of a particle's behaviour as it successively encounters several resonances. The model is applicable to many scenarios, including (i) Planet migration through gas discs trapping other planets or planetesimals in resonances; (ii) Planet migration through a debris disc; (iii) Dust migration through PR drag. The Hamiltonian model will allow quick interpretation of the resonant properties of extrasolar planets and Kuiper Belt Objects, and will allow synthetic images of debris disc structures to be quickly generated, which will be useful for predicting and interpreting disc images made with ALMA, Darwin/TPF or similar missions. Full details can be found in Mustill & Wyatt (2011).

scholarly journals Oscillatory dynamics in a bacterial cross-protection mutualism

2016 ◽  
Vol 113 (22) ◽  
pp. 6236-6241 ◽  
Author(s):  
Eugene Anatoly Yurtsev ◽  
Arolyn Conwill ◽  
Jeff Gore
Keyword(s):  
Evolutionary Dynamics ◽  
Cooperative Behavior ◽  
Cross Protection ◽  
Common Mechanism ◽  
Natural Environments ◽  
Term Survival ◽  
Bacterial Populations ◽  
Oscillatory Dynamics ◽  
Protection Mutualism

Cooperation between microbes can enable microbial communities to survive in harsh environments. Enzymatic deactivation of antibiotics, a common mechanism of antibiotic resistance in bacteria, is a cooperative behavior that can allow resistant cells to protect sensitive cells from antibiotics. Understanding how bacterial populations survive antibiotic exposure is important both clinically and ecologically, yet the implications of cooperative antibiotic deactivation on the population and evolutionary dynamics remain poorly understood, particularly in the presence of more than one antibiotic. Here, we show that two Escherichia coli strains can form an effective cross-protection mutualism, protecting each other in the presence of two antibiotics (ampicillin and chloramphenicol) so that the coculture can survive in antibiotic concentrations that inhibit growth of either strain alone. Moreover, we find that daily dilutions of the coculture lead to large oscillations in the relative abundance of the two strains, with the ratio of abundances varying by nearly four orders of magnitude over the course of the 3-day period of the oscillation. At modest antibiotic concentrations, the mutualistic behavior enables long-term survival of the oscillating populations; however, at higher antibiotic concentrations, the oscillations destabilize the population, eventually leading to collapse. The two strains form a successful cross-protection mutualism without a period of coevolution, suggesting that similar mutualisms may arise during antibiotic treatment and in natural environments such as the soil.

scholarly journals Antagonism and population dynamics of Acinetobacter baumannii from US military treatment centers

2017 ◽  
Author(s):  
Rae A Heitkamp ◽  
Amy M Zale ◽  
Benjamin C Kirkup
Keyword(s):  
Population Dynamics ◽  
Acinetobacter Baumannii ◽  
Bacterial Species ◽  
Hospital Setting ◽  
Antagonistic Activity ◽  
Resistant Bacteria ◽  
Natural Environments ◽  
Bacterial Populations ◽  
Starting Point ◽  
Before And After

Antibiotic-resistant bacteria complicate many infections and can be difficult to eradicate from hospitals. The population dynamics and ecology of these organisms in the hospital setting, however, is not well understood. Here, we report extensive strain-based antagonistic interactions occurring in military clinical isolates of Acinetobacter baumannii, a bacterial species that causes many drug-resistant hospital-associated infections. Sequence-based phylogenetic analysis of isolates allowed for differentiation to two major clades, with one of the clades representing two closely related genetic groups. Antagonistic activity was detected using a spot-plate assay to test pairwise interactions of all isolates. Isolates exhibited extensive and diverse patterns of antagonism against other isolates. One major clade of isolates had a distinct change in antagonism phenotype between isolates that differed by one base pair out of ~1500bp sequenced, with consistent antagonism of one group of isolates by the other. Both the antagonistic and the sensitive group exhibited extensive drug resistance. The first isolate of the antagonistic group was cultured in May 2010. The proportion of isolates from the antagonistic group collected before and after July 2010 increased from 2% to 76%. The results of this early study of the ecology of hospital-associated bacterial populations are discussed in the context of the species ecology of bacteria in natural environments. This work is a potential starting point for investigations into ecological interventions for infection control in hospitals.

scholarly journals Family Businesses during the COVID-19 Crisis – Evidence from Poland

2020 ◽  
Vol 54 (3) ◽  
pp. 101
Author(s):  
Robert Zajkowski ◽  
Beata Żukowska
Keyword(s):  
Research Methods ◽  
Family Firms ◽  
Ad Hoc ◽  
Theoretical Background ◽  
Vital Role ◽  
Family Businesses ◽  
Primary Data ◽  
Probability Of Survival ◽  
Fractal Analyses ◽  
Business Entities

<p>Theoretical background: Family businesses are a specific group of enterprises in which family bonds play a vital role in determining the economic and noneconomic goals of the business. The subject literature emphasises the long-term focus of family businesses which is on continuity, futurity and perseverance. During the COVID-19 crisis, unique family business traits can allow these entities to access useful resources and take positive actions such as forging strong networking relationships, tapping into local idiosyncratic knowledge, exercising rapid response, having flexibility and exercising trust with caution. This suggests that family businesses might also react to the COVID-19 crisis in their own distinctive ways using their unique attributes.</p><p>Purpose of the article: In this paper we will show how family businesses deal with coronavirus restrictions and what measures they undertook during this challenging period. The paper is organised around four research questions.</p><p>Research methods: This research was conducted using a sample of 167 family businesses. Primary data related to reactions of family businesses facing the COVID-19 crisis were collected in April and at the beginning of May 2020. To achieve the goals of this study, we carried out such research methods and procedures as fractal analyses, descriptive statistics, statistical comparison of means and subjective classification of the factors.</p><p>Main findings: For family businesses, a sudden fall in revenue was a common result of COVID-19 restrictions in the Polish economy. In the case of the majority of surveyed family fims, revenues fell by 44%, and in the next 2 to 3 months businesses expected additional decreases of 39.8%. More than 65% declared a stable level of employment, but more than a quarter of surveyed family firms showed an average dip in firm employment of 15.7% and expected further job losses at around 13.1%. To protect businesses against the negative effects of the pandemic, surveyed family firms undertook several <em>ad hoc</em> measures. We divided the analysed reactions to COVID into three groups: proactive, neutral and progressive. We noticed that the most common measures were those marked as “neutral”, or those which neither expanded nor retrenched the business in the short term. This observation suggests that family businesses might choose “persevering” as their first strategic response to the sudden crisis. We also found that “proactive” measures were undertaken in family businesses which evaluated their probability of survival as higher than businesses that indicated “neutral” or “defensive” reactions. In addition, we isolated statistically significant differences in family fims’ average probability of survival among the firms which introduced particular neutral and defensive measures and those which did not. On this basis we can conclude that the lower the perceived probability of survival is, the more retrenchment-oriented types of measures begin to be taken. Additionally, it should be mentioned that so-called anti-crisis shields implemented by the Polish government were assessed as inadequately supportive of business entities’ survival.</p>

scholarly journals Population Dynamics of Phenol-Degrading Bacteria in Activated Sludge Determined by gyrB-Targeted Quantitative PCR

1998 ◽  
Vol 64 (4) ◽  
pp. 1203-1209 ◽  
Author(s):  
Kazuya Watanabe ◽  
Satoshi Yamamoto ◽  
Sanae Hino ◽  
Shigeaki Harayama
Keyword(s):  
Population Dynamics ◽  
Activated Sludge ◽  
Quantitative Pcr ◽  
Pcr Amplification ◽  
Plate Count ◽  
Bacterial Populations ◽  
Pcr Product ◽  
Degrading Bacteria ◽  
Pcr Method ◽  
Kinetics Of

ABSTRACT A method for quantifying bacterial populations introduced into an activated-sludge microbial community is described. The method involves extraction of DNA from activated sludge, appropriate dilution of the extracted DNA with DNA extracted from nonintroduced activated sludge, PCR amplification of a gyrB gene fragment from the introduced strain with a set of strain-specific primers, and quantification of the electrophoresed PCR product by densitometry. The adequacy of the method was examined by analyzing the population dynamics of two phenol-degrading bacteria, Pseudomonas putida BH and Comamonas sp. strain E6, that had been introduced into phenol-digesting activated sludge. The density of each of the two populations determined by the PCR method immediately after the introduction was consistent with the density estimated from a plate count of the inoculum. This quantitative PCR method revealed different population dynamics for the two strains in the activated sludge under different phenol-loading conditions. The behavior of both of these strains in the activated sludge reflected the growth kinetics of the strains determined in laboratory axenic cultures.

scholarly journals Transmission time delays organize the brain network synchronization

2019 ◽  
Vol 377 (2153) ◽  
pp. 20180132 ◽  
Author(s):  
Spase Petkoski ◽  
Viktor K. Jirsa
Keyword(s):  
Time Delays ◽  
Phase Synchronization ◽  
Brain Regions ◽  
Brain Network ◽  
Temporal Organization ◽  
Delay Systems ◽  
Oscillatory Dynamics ◽  
Wide Range ◽  
Kuramoto Oscillators ◽  
The Brain

The timing of activity across brain regions can be described by its phases for oscillatory processes, and is of crucial importance for brain functioning. The structure of the brain constrains its dynamics through the delays due to propagation and the strengths of the white matter tracts. We use self-sustained delay-coupled, non-isochronous, nonlinearly damped and chaotic oscillators to study how spatio-temporal organization of the brain governs phase lags between the coherent activity of its regions. In silico results for the brain network model demonstrate a robust switching from in- to anti-phase synchronization by increasing the frequency, with a consistent lagging of the stronger connected regions. Relative phases are well predicted by an earlier analysis of Kuramoto oscillators, confirming the spatial heterogeneity of time delays as a crucial mechanism in shaping the functional brain architecture. Increased frequency and coupling are also shown to distort the oscillators by decreasing their amplitude, and stronger regions have lower, but more synchronized activity. These results indicate specific features in the phase relationships within the brain that need to hold for a wide range of local oscillatory dynamics, given that the time delays of the connectome are proportional to the lengths of the structural pathways. This article is part of the theme issue ‘Nonlinear dynamics of delay systems’.

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