Chemotaxis: how bacteria use memory

2009 ◽  
Vol 390 (11) ◽  
Author(s):  
Nikita Vladimirov ◽  
Victor Sourjik
Keyword(s):  
Large Range ◽  
Bacterial Chemotaxis ◽  
Bacterial Cells ◽  
Molecular Memory ◽  
Gradient Sensing ◽  
Chemical Gradients ◽  
The Past ◽  
Memory Time ◽  
Temporal Mode ◽  
Theoretical Analyses

AbstractBacterial chemotaxis represents one of the simplest and best studied examples of unicellular behavior. Chemotaxis allows swimming bacterial cells to follow chemical gradients in the environment by performing temporal comparisons of ligand concentrations. The process of chemotaxis in the model bacteriumEscherichia colihas been studied in great molecular detail over the past 40 years, using a large range of experimental tools to investigate physiology, genetics and biochemistry of the system. The abundance of quantitative experimental data enabled detailed computational modeling of the pathway and theoretical analyses of such properties as robustness and signal amplification. Because of the temporal mode of gradient sensing in bacterial chemotaxis, molecular memory is an essential component of the chemotaxis pathway. Recent studies suggest that the memory time scale has been evolutionary optimized to perform optimal comparisons of stimuli while swimming in the gradient. Moreover, noise in the adaptation system, which results from variations of the adaptation rate both over time and among cells, might be beneficial for the overall chemotactic performance of the population.

scholarly journals Networked Chemoreceptors Benefit Bacterial Chemotaxis Performance

mBio ◽  
2016 ◽  
Vol 7 (6) ◽  
Author(s):  
Vered Frank ◽  
Germán E. Piñas ◽  
Harel Cohen ◽  
John S. Parkinson ◽  
Ady Vaknin
Keyword(s):  
Dynamic Range ◽  
Bacterial Chemotaxis ◽  
Detection Sensitivity ◽  
Functional Coupling ◽  
Bacterial Cells ◽  
Communication Interface ◽  
E Coli ◽  
Chemical Gradients ◽  
Receptor Complexes ◽  
Motile Bacteria

ABSTRACTMotile bacteria use large receptor arrays to detect and follow chemical gradients in their environment. Extended receptor arrays, composed of networked signaling complexes, promote cooperative stimulus control of their associated signaling kinases. Here, we used structural lesions at the communication interface between core complexes to create anEscherichia colistrain with functional but dispersed signaling complexes. This strain allowed us to directly study how networking of signaling complexes affects chemotactic signaling and gradient-tracking performance. We demonstrate that networking of receptor complexes provides bacterial cells with about 10-fold-heightened detection sensitivity to attractants while maintaining a wide dynamic range over which receptor adaptational modifications can tune response sensitivity. These advantages proved especially critical for chemotaxis toward an attractant source under conditions in which bacteria are unable to alter the attractant gradient.IMPORTANCEChemoreceptor arrays are found in many motile bacteria. However, although our understanding of bacterial chemotaxis is quite detailed, the signaling and behavioral advantages of networked receptor arrays had not been directly studied in cells. We have recently shown that lesions in a key interface of theE. colireceptor array diminish physical connections and functional coupling between core signaling complexes while maintaining their basic signaling capacity. In this study, we exploited an interface 2 mutant to show, for the first time, that coupling between core complexes substantially enhances stimulus detection and chemotaxis performance.

Feminist (Theatre) Historiography / Canadian (Feminist) Theatre: A Reading of some Practices and Theories

1992 ◽  
Vol 13 (1) ◽  
pp. 144-151
Author(s):  
Susan Bennett
Keyword(s):  
Position Paper ◽  
Theory And Practice ◽  
Feminist Theatre ◽  
The Past ◽  
Key Issues ◽  
Theatre Historiography ◽  
Theoretical Analyses ◽  
Extended Discussion

Through this position paper the author seeks to provide a focus for extended discussion of some of the key issues arising from feminist approaches to theatre research. She indicates some of the insights made possible by feminist theoretical analyses of theatre historiography as well as some of the implications of the various positions inscribed in articles on Canadian feminist theatre historiography over the past ten years. The author hopes to facilitate more discussion of the wide variety of feminist challenges to and transformation of the theory and practice of theatre research and theatre historiography.

scholarly journals Old concepts, new molecules and current approaches applied to the bacterial nucleotide signalling field

2016 ◽  
Vol 371 (1707) ◽  
pp. 20150503 ◽  
Author(s):  
Angelika Gründling ◽  
Vincent T. Lee
Keyword(s):  
Mass Spectrometry ◽  
Rapid Identification ◽  
Screening Methods ◽  
Bacterial Cells ◽  
The Novel ◽  
Specific Receptor ◽  
Receptor Proteins ◽  
The Past ◽  
Genome Wide ◽  
Cellular Pathways

Signalling nucleotides are key molecules that help bacteria to rapidly coordinate cellular pathways and adapt to changes in their environment. During the past 10 years, the nucleotide signalling field has seen much excitement, as several new signalling nucleotides have been discovered in both eukaryotic and bacterial cells. The fields have since advanced quickly, aided by the development of important tools such as the synthesis of modified nucleotides, which, combined with sensitive mass spectrometry methods, allowed for the rapid identification of specific receptor proteins along with other novel genome-wide screening methods. In this review, we describe the principle concepts of nucleotide signalling networks and summarize the recent work that led to the discovery of the novel signalling nucleotides. We also highlight current approaches applied to the research in the field as well as resources and methodological advances aiding in a rapid identification of nucleotide-specific receptor proteins. This article is part of the themed issue ‘The new bacteriology’.

scholarly journals Chemoreceptors in Caulobacter crescentus: Trimers of Receptor Dimers in a Partially Ordered Hexagonally Packed Array

2008 ◽  
Vol 190 (20) ◽  
pp. 6805-6810 ◽  
Author(s):  
Cezar M. Khursigara ◽  
Xiongwu Wu ◽  
Sriram Subramaniam
Keyword(s):  
Caulobacter Crescentus ◽  
Electron Tomography ◽  
Bacterial Chemotaxis ◽  
Bacterial Cells ◽  
Molecular Architecture ◽  
Cellular Motility ◽  
Partially Ordered ◽  
Order And Disorder ◽  
Cryo Electron Tomography ◽  
Receptor Dimers

ABSTRACT Chemoreceptor arrays are macromolecular complexes that form extended assemblies primarily at the poles of bacterial cells and mediate chemotaxis signal transduction, ultimately controlling cellular motility. We have used cryo-electron tomography to determine the spatial distribution and molecular architecture of signaling molecules that comprise chemoreceptor arrays in wild-type Caulobacter crescentus cells. We demonstrate that chemoreceptors are organized as trimers of receptor dimers, forming partially ordered hexagonally packed arrays of signaling complexes in the cytoplasmic membrane. This novel organization at the threshold between order and disorder suggests how chemoreceptors and associated molecules are arranged in signaling assemblies to respond dynamically in the activation and adaptation steps of bacterial chemotaxis.

Poetics of novel of A.N. Varlamov the “Soul my Paul”

2018 ◽  
Vol 7 (6) ◽  
pp. 57-64
Author(s):  
В. Серафимова ◽  
V. Serafimova
Keyword(s):  
Large Range ◽  
The Novel ◽  
The Past

The article deals with the composition of the new Chapter of the novel "my soul Paul", which consists of five parts, divided into chapters, and explores a large range of problems. Compositional clarity gives the novel intertwining storylines, United through the theme, the theme of the past, its relationship with the present and future, the theme of memory, the concept Of man-Creator, capable of self-improvement. The novel presents interesting examples of solving communicative problems, creating communicative situations.

scholarly journals How receptor diffusion influences gradient sensing

2015 ◽  
Vol 12 (102) ◽  
pp. 20141097 ◽  
Author(s):  
H. Nguyen ◽  
P. Dayan ◽  
G. J. Goodhill
Keyword(s):  
Fisher Information ◽  
Diffusion Constant ◽  
Theoretical Models ◽  
Eukaryotic Cells ◽  
Biological Processes ◽  
Directed Motion ◽  
Gradient Sensing ◽  
Chemical Gradients ◽  
Physical Limit ◽  
Spatial Differences

Chemotaxis, or directed motion in chemical gradients, is critical for various biological processes. Many eukaryotic cells perform spatial sensing, i.e. they detect gradients by comparing spatial differences in binding occupancy of chemosensory receptors across their membrane. In many theoretical models of spatial sensing, it is assumed, for the sake of simplicity, that the receptors concerned do not move. However, in reality, receptors undergo diverse modes of diffusion, and can traverse considerable distances in the time it takes such cells to turn in an external gradient. This sets a physical limit on the accuracy of spatial sensing, which we explore using a model in which receptors diffuse freely over the membrane. We find that the Fisher information carried in binding and unbinding events decreases monotonically with the diffusion constant of the receptors.

scholarly journals Physical limits on bacterial navigation in dynamic environments

2016 ◽  
Vol 13 (114) ◽  
pp. 20150844 ◽  
Author(s):  
Andrew M. Hein ◽  
Douglas R. Brumley ◽  
Francesco Carrara ◽  
Roman Stocker ◽  
Simon A. Levin
Keyword(s):  
Swimming Speed ◽  
Aquatic Ecosystems ◽  
Outer Boundary ◽  
Dynamic Environments ◽  
Square Root ◽  
Bacterial Cells ◽  
Chemical Concentration ◽  
Gradient Sensing ◽  
Temporal Gradient ◽  
Rigorous Method

Many chemotactic bacteria inhabit environments in which chemicals appear as localized pulses and evolve by processes such as diffusion and mixing. We show that, in such environments, physical limits on the accuracy of temporal gradient sensing govern when and where bacteria can accurately measure the cues they use to navigate. Chemical pulses are surrounded by a predictable dynamic region, outside which bacterial cells cannot resolve gradients above noise. The outer boundary of this region initially expands in proportion to the square root of time before rapidly contracting. Our analysis also reveals how chemokinesis—the increase in swimming speed many bacteria exhibit when absolute chemical concentration exceeds a threshold—may serve to enhance chemotactic accuracy and sensitivity when the chemical landscape is dynamic. More generally, our framework provides a rigorous method for partitioning bacteria into populations that are ‘near’ and ‘far’ from chemical hotspots in complex, rapidly evolving environments such as those that dominate aquatic ecosystems.

scholarly journals Universal Response-Adaptation Relation in Bacterial Chemotaxis

2014 ◽  
Vol 197 (2) ◽  
pp. 307-313 ◽  
Author(s):  
Anna K. Krembel ◽  
Silke Neumann ◽  
Victor Sourjik
Keyword(s):  
Short Term Memory ◽  
Bacterial Chemotaxis ◽  
Fine Tuning ◽  
Universal Relation ◽  
Short Term ◽  
Content Type ◽  
Cooperative Interactions ◽  
Memory Time ◽  
Chemotaxis Receptors ◽  
Activity Dependent

The bacterial strategy of chemotaxis relies on temporal comparisons of chemical concentrations, where the probability of maintaining the current direction of swimming is modulated by changes in stimulation experienced during the recent past. A short-term memory required for such comparisons is provided by the adaptation system, which operates through the activity-dependent methylation of chemotaxis receptors. Previous theoretical studies have suggested that efficient navigation in gradients requires a well-defined adaptation rate, because the memory time scale needs to match the duration of straight runs made by bacteria. Here we demonstrate that the chemotaxis pathway ofEscherichia colidoes indeed exhibit a universal relation between the response magnitude and adaptation time which does not depend on the type of chemical ligand. Our results suggest that this alignment of adaptation rates for different ligands is achieved through cooperative interactions among chemoreceptors rather than through fine-tuning of methylation rates for individual receptors. This observation illustrates a yet-unrecognized function of receptor clustering in bacterial chemotaxis.

The Christology of Wolfhart Pannenberg

1967 ◽  
Vol 3 (1) ◽  
pp. 369-376 ◽  
Author(s):  
G. G. O'Collins
Keyword(s):  
Large Range ◽  
The Past ◽  
Wolfhart Pannenberg ◽  
The Way

One of the most interesting works on Christology to appear in recent years is Wolfhart Pannenberg's Grundzüge der Christologie. The reviewer in the Scottish Journal of Theology could speak of it as ‘a theological thriller’ and ‘very satisfying on account of its erudition, constant confrontation with Roman and Protestant, German and non-German theologians of the past and present’. Certainly we have here a Christology based on a striking knowledge of Scripture, the Councils, the Fathers and a large range of theologians and philosophers, both ancient and modern. Its originality consists perhaps most of all in the way it understands Christ's role as Revealer.

scholarly journals Discovery and development of new antimicrobial agents.

1990 ◽  
Vol 3 (1) ◽  
pp. 13-31 ◽  
Author(s):  
T D Gootz
Keyword(s):  
Bacterial Resistance ◽  
Antimicrobial Agents ◽  
Bacterial Cells ◽  
Beta Lactams ◽  
Resistance Development ◽  
Safety Testing ◽  
The Past ◽  
Body Of Knowledge ◽  
New Antibiotics ◽  
The Impact

The unprecedented growth in the number of new antibiotics over the past two decades has been the result of extensive research efforts that have exploited the growing body of knowledge describing the interactions of antibiotics with their targets in bacterial cells. Information gained from one class of antimicrobial agents has often been used to advance the development of other classes. In the case of beta-lactams, information on structure-activity relationships gleaned from penicillins and cephalosporins was rapidly applied to the cephamycins, monobactams, penems, and carbapenems in order to discover broad-spectrum agents with markedly improved potency. These efforts have led to the introduction of many new antibiotics that demonstrate outstanding clinical efficacy and improved pharmacokinetics in humans. The current review discusses those factors that have influenced the rapid proliferation of new antimicrobial agents, including the discovery of new lead structures from natural products and the impact of bacterial resistance development in the clinical setting. The development process for a new antibiotic is discussed in detail, from the stage of early safety testing in animals through phase I, II, and III clinical trials.

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