scholarly journals Extent of adaptation is not limited by unpredictability of the environment in laboratory populations of Escherichia coli

2017 ◽  
Author(s):  
Shraddha Karve ◽  
Devika Bhave ◽  
Sutirth Dey
Keyword(s):  
Escherichia Coli ◽  
Environmental Variability ◽  
Acidic Ph ◽  
Simultaneous Presence ◽  
Environmental Stressor ◽  
The Earth ◽  
Fluctuating Environments ◽  
Environmental Fluctuations ◽  
Laboratory Populations ◽  
Different Parts

AbstractEnvironmental variability is on the rise in different parts of the earth and the survival of many species depend on how well they cope with these fluctuations. Our current understanding of how organisms adapt to unpredictably fluctuating environments is almost entirely based on studies that investigate fluctuations among different values of a single environmental stressor like temperature or pH. However, in nature multiple stresses often exist simultaneously. How would unpredictability in environmental fluctuations affect adaptation under such a scenario? To answer this question, we subjected laboratory populations of Escherichia coli to selection over ~260 generations. The populations faced predictable and unpredictable environmental fluctuations across qualitatively different selection environments, namely, salt and acidic pH. We show that predictability of environmental fluctuations does not play a role in determining the extent of adaptation. Interestingly, the extent of ancestral adaptation, to the chosen selection environments, is of key importance. Integrating the insights from two previous studies, our results suggest that it is the simultaneous presence of multiple environmental factors that poses a bigger constraint on extent of adaptation, rather than unpredictability of the fluctuations.

scholarly journals Breaking through evolutionary constraint by environmental fluctuations

2015 ◽  
Author(s):  
Marjon GJ de Vos ◽  
Alexandre Dawid ◽  
Vanda Sunderlikova ◽  
Sander J Tans
Keyword(s):  
Escherichia Coli ◽  
Environmental Variability ◽  
Model System ◽  
Evolutionary Constraint ◽  
Apparent Paradox ◽  
Epistatic Interactions ◽  
Genetic Constraints ◽  
Trade Offs ◽  
Fluctuating Environments ◽  
Genetic Constraint

Epistatic interactions can frustrate and shape evolutionary change. Indeed, phenotypes may fail to evolve because essential mutations can only be selected positively if fixed simultaneously. How environmental variability affects such constraints is poorly understood. Here we studied genetic constraints in fixed and fluctuating environments, using theEscherichia coli lacoperon as a model system for genotype-environment interactions. The data indicated an apparent paradox: in different fixed environments, mutational trajectories became trapped at sub-optima where no further improvements were possible, while repeated switching between these same environments allowed unconstrained adaptation by continuous improvements. Pervasive cross-environmental trade-offs transformed peaks into valleys upon environmental change, thus enabling escape from entrapment. This study shows that environmental variability can lift genetic constraint, and that trade-offs not only impede but can also facilitate adaptive evolution.

scholarly journals Escherichia colipopulations adapt to complex, unpredictable fluctuations without any trade-offs across environments

2016 ◽  
Author(s):  
Shraddha Karve ◽  
Devika Bhave ◽  
Dhanashri Nevgi ◽  
Sutirth Dey
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Growth Rates ◽  
Complex Environments ◽  
Multiple Stresses ◽  
Trade Off ◽  
Trade Offs ◽  
Fluctuating Environments ◽  
Laboratory Populations ◽  
Lower Variation

AbstractIn nature, organisms are simultaneously exposed to multiple stresses (i.e. complex environments) that often fluctuate unpredictably. While both these factors have been studied in isolation, the interaction of the two remains poorly explored. To address this issue, we selected laboratory populations ofEscherichia coliunder complex (i.e. stressful combinations of pH, H2O2and NaCl) unpredictably fluctuating environments for ~900 generations. We compared the growth rates and the corresponding trade-off patterns of these populations to those that were selected under constant values of the component stresses (i.e. pH, H2O2and NaCl) for the same duration. The fluctuation-selected populations had greater mean growth rate and lower variation for growth rate over all the selection environments experienced. However, while the populations selected under constant stresses experienced severe tradeoffs in many of the environments other than those in which they were selected, the fluctuation-selected populations could by-pass the across-environment trade-offs completely. Interestingly, trade-offs were found between growth rates and carrying capacities. The results suggest that complexity and fluctuations can strongly affect the underlying trade-off structure in evolving populations.

scholarly journals Evolutionary contingency’s impact on laboratory evolution ofEscherichia coliunder fluctuating environments

2019 ◽  
Author(s):  
Ximo Pechuan ◽  
Daniel Biro ◽  
Maryl Lambros ◽  
Aviv Bergman
Keyword(s):  
Escherichia Coli ◽  
Environmental Conditions ◽  
Phenotypic Characterization ◽  
General Tendency ◽  
Environmental Fluctuation ◽  
Laboratory Evolution ◽  
Phenotypic Response ◽  
Final Population ◽  
Fluctuating Environments ◽  
Environmental Fluctuations

1AbstractThe adaptation of biological organisms to fluctuating environments is one major determinant of their structural and dynamical complexity. Organisms have evolved devoted adaptations to ensure the robust performance of physiological functions under environmental fluctuations. To further our understanding of particular adaptation strategies to different environmental fluctuations, we perform laboratory evolution experiments ofEscherichia coliunder three temperature fluctuation regimes alternating between 15°C and 43°C. Two of these regimes are determined by the population’s growth, while the third regime switches stochastically. To address evolutionary contingencies, the experiments are performed on two lineages departing from different genetic backgrounds. The two lineages display distinct evolutionary trajectories, demonstrating dependency on the starting strain’s genetic background. Several genes exhibit a high degree of parallelism, suggesting their potential adaptive nature. The growth increase of the representative clones from each final population relative to their ancestor at 15°C and 43°C demonstrated no correlation between both temperatures, insinuating an absence of a strong trade-off between these two temperatures. Some had a growth rate decrease at 15°C unless exposed to a 43°C epoch, indicating some degree of internalization of the structure of the environment fluctuations. The phenotypic response of the evolved clones at 15°C and 43°C was assessed by a phenotype array method. The resulting responses reveal a general tendency to move closer to the phenotypic response of our starting strains at the optimum of 37°C. This observation expands the documented restorative responses, even when facing complex environmental conditions.2Author SummaryLaboratory evolution experiments have been widely employed to test hypotheses from evolutionary theory. To assess the dynamics of adaptation under environmental fluctuations, we evolved 24Escherichia colipopulations under different regimes of temperature switching between 15°C and 43°C for about 600 generations. At the final point of the evolution experiment, the evolved populations were genome sequenced and clones were isolated and sequenced for phenotypic characterization. Fitness measurements revealed adaptation to both environmental conditions and some strains internalized the environmental fluctuation. Array phenotypic measurements showed that the majority of evolved strains tended to restore the phenotypic signature of the perturbed environments to that of the optimal temperature condition. This observation expands the documented restorative responses, even when facing complex environmental conditions.

scholarly journals E. colipopulations in unpredictably fluctuating environments evolve to face novel stresses through enhanced efflux activity

2014 ◽  
Author(s):  
Shraddha Madhav Karve ◽  
Sachit Daniel ◽  
Yashraj Chavhan ◽  
Abhishek Anand ◽  
Somendra Singh Kharola ◽  
...  
Keyword(s):  
Environmental Variables ◽  
Environmental Variability ◽  
Broad Spectrum Antibiotic ◽  
E Coli ◽  
Fluctuating Environments ◽  
Laboratory Populations ◽  
Alternate Mechanism ◽  
Multiple Variables ◽  
Selection For ◽  
Energy Dependent

There is considerable understanding about how laboratory populations respond to predictable (constant or deteriorating-environment) selection for single environmental variables like temperature or pH. However, such insights may not apply when selection environments comprise multiple variables that fluctuate unpredictably, as is common in nature. To address this issue, we grew replicate laboratory populations ofE. coliin nutrient broth whose pH and concentrations of salt (NaCl) and hydrogen peroxide (H2O2) were randomly changed daily. After ~170 generations, the fitness of the selected populations had not increased in any of the three selection environments. However, these selected populations had significantly greater fitness in four novel environments which have no known fitness-correlation with tolerance to pH, NaCl or H2O2. Interestingly, contrary to expectations, hypermutators did not evolve. Instead, the selected populations evolved an increased ability for energy dependent efflux activity that might enable them to throw out toxins, including antibiotics, from the cell at a faster rate. This provides an alternate mechanism for how evolvability can evolve in bacteria and potentially lead to broad-spectrum antibiotic resistance, even in the absence of prior antibiotic exposure. Given that environmental variability is increasing in nature, this might have serious consequences for public-health.

scholarly journals Escherichia coli populations adapt to complex, unpredictable fluctuations by minimizing trade-offs across environments

2016 ◽  
Author(s):  
Shraddha Madhav Karve ◽  
Devika Bhave ◽  
Dhanashri Nevgi ◽  
Sutirth Dey
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Growth Rates ◽  
Complex Environments ◽  
Multiple Stresses ◽  
Trade Off ◽  
Trade Offs ◽  
Fluctuating Environments ◽  
Laboratory Populations ◽  
Lower Variation

In nature, organisms are simultaneously exposed to multiple stresses (i.e. complex environments) that often fluctuate unpredictably. While both these factors have been studied in isolation, the interaction of the two remains poorly explored. To address this issue, we selected laboratory populations of Escherichia coli under complex (i.e. stressful combinations of pH, H2O2 and NaCl) unpredictably fluctuating environments for ~900 generations. We compared the growth rates and the corresponding trade-off patterns of these populations to those that were selected under constant values of the component stresses (i.e. pH, H2O2 and NaCl) for the same duration. The fluctuation-selected populations had greater mean growth rate and lower variation for growth rate over all the selection environments experienced. However, while the populations selected under constant stresses experienced trade-offs in the environments other than those in which they were selected, the fluctuation-selected populations could by-pass the across-environment trade-offs almost entirely. Interestingly, trade-offs were found between growth rates and carrying capacities. The results suggest that complexity and fluctuations can strongly affect the underlying trade-off structure in evolving populations.

scholarly journals Mean Value and Variability of Fish Catches in Fluctuating Environments

1976 ◽  
Vol 33 (1) ◽  
pp. 189-193 ◽  
Author(s):  
M. Gatto ◽  
S. Rinaldi
Keyword(s):  
Environmental Variability ◽  
Mean Value ◽  
Maximum Deviation ◽  
Fishing Strategies ◽  
Fluctuating Environments ◽  
Environmental Fluctuations ◽  
Stock Recruitment ◽  
The Mean ◽  
Recruitment Model ◽  
Constant Escapement

The mean value of the catch and its variability due to environmental fluctuations are analyzed for a very general stock-recruitment model. Particular attention is devoted to the comparison of two standard fishing strategies (constant effort and constant escapement) in terms of mean catch, variance in catches, and maximum deviation of catch. It is demonstrated analytically that constant escapement policies should always give higher mean catch, but should give higher catch variance and more extreme catches only under certain conditions of environmental variability.

scholarly journals Molecular Hydrogen Formation by Escherichia Coli Hydrogenase 3 during Fermentation of Glucose at Slightly Acidic pH

2011 ◽  
Vol 100 (3) ◽  
pp. 488a
Author(s):  
Anna Poladyan ◽  
Anna Poghosyan ◽  
Karen Trchounian ◽  
Armen Trchounian
Keyword(s):  
Escherichia Coli ◽  
Molecular Hydrogen ◽  
Acidic Ph ◽  
Hydrogen Formation ◽  
Hydrogenase 3

scholarly journals XII. On the cause of the discrepancies observed by Mr. Baily with the Cavendish apparatus for determining the mean density of the earth

1847 ◽  
Vol 137 ◽  
pp. 217-229 ◽  
Keyword(s):  
Mathematical Theory ◽  
Full Account ◽  
Astronomical Society ◽  
Royal Astronomical Society ◽  
The Earth ◽  
Singular Source ◽  
The Mean ◽  
The Masses ◽  
Source Of Error ◽  
Different Parts

In the Fourteenth Volume of the Transactions of the Royal Astronomical Society will be found a full account of the Cavendish apparatus, and of the mode of experimenting followed by Mr. Baily. It will therefore not be necessary for me, in this place, to enter into any detail as to the different parts of the instrument, and the various precautions adopted in order to avoid that singular source of error 'currents of air in the torsion box arising from unequal temperature,’ which had been discovered by Cavendish. It will be sufficient for me to state that all the arrangements are of a highly satisfactory kind, and that I am of opinion that no aerial currents could have existed in the torsion box. The deduction of the mean density of the earth from the observed vibrations of the balls influenced by the torsion force and the attraction of the masses, is founded on a mathematical theory of the motion of the balls given by the Astronomer Royal, Mr. Airy ; and as this theory is certainly insufficient to account for the discrepancies, it will here be necessary to give a brief sketch of it.

Acid-stimulated bioassembly of high-performance quantum dots in Escherichia coli

2019 ◽  
Vol 7 (31) ◽  
pp. 18480-18487 ◽  
Author(s):  
Li-Jiao Tian ◽  
Wen-Wei Li ◽  
Ting-Ting Zhu ◽  
Guo-Hua Zhao ◽  
Xian-Wei Liu ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Quantum Dots ◽  
High Performance ◽  
Acidic Ph ◽  
Non Destructive

Acidic pH stimulated bio-assembly of CdSxSe1−x Bio-QDs which showed good performance for non-destructive bioimaging of zebrafish.

scholarly journals The germicidal effect of the open air in different parts of The Netherlands

1977 ◽  
Vol 78 (2) ◽  
pp. 175-187 ◽  
Author(s):  
G. de Mik ◽  
Ida de Groot
Keyword(s):  
Escherichia Coli ◽  
The Netherlands ◽  
Wind Direction ◽  
Traffic Intensity ◽  
Industrial Areas ◽  
Different Parts

SUMMARYUsing the microthread technique the survival ofEscherichia coliMRE 162 in open air was measured in different parts of The Netherlands.The presence of bactericidal compounds (open air factor = OAF) could be demonstrated on several days and quantitated in relative units of OAF concentration.In the absence of ozone the OAF concentration was always low. In the presence of ozone the OAF concentration was dependent on wind direction. At the selected microthread exposure sites air from areas with high traffic intensity contributed more to OAF production than air from industrial areas. OAF production is probably related to the nature of hydrocarbons in the air.

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