Chemotaxis in Escherichia coli analysed by Three-dimensional Tracking
TL;DR: Chemotaxis toward amino-acids results from the suppression of directional changes which occur spontaneously in isotropic solutions.
Abstract: Chemotaxis toward amino-acids results from the suppression of directional changes which occur spontaneously in isotropic solutions.
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TL;DR: A computer program that emulates the distributed optimization process represented by the activity of social bacterial foraging is presented and applied to a simple multiple-extremum function minimization problem and briefly discusses its relationship to some existing optimization algorithms.
Abstract: We explain the biology and physics underlying the chemotactic (foraging) behavior of E. coli bacteria. We explain a variety of bacterial swarming and social foraging behaviors and discuss the control system on the E. coli that dictates how foraging should proceed. Next, a computer program that emulates the distributed optimization process represented by the activity of social bacterial foraging is presented. To illustrate its operation, we apply it to a simple multiple-extremum function minimization problem and briefly discuss its relationship to some existing optimization algorithms. The article closes with a brief discussion on the potential uses of biomimicry of social foraging to develop adaptive controllers and cooperative control strategies for autonomous vehicles. For this, we provide some basic ideas and invite the reader to explore the concepts further.
2,917 citations
TL;DR: In this article, the authors provide a guided tour through the development of artificial self-propelling microparticles and nanoparticles and their application to the study of nonequilibrium phenomena, as well as the open challenges that the field is currently facing.
Abstract: Differently from passive Brownian particles, active particles, also known as self-propelled Brownian particles or microswimmers and nanoswimmers, are capable of taking up energy from their environment and converting it into directed motion. Because of this constant flow of energy, their behavior can be explained and understood only within the framework of nonequilibrium physics. In the biological realm, many cells perform directed motion, for example, as a way to browse for nutrients or to avoid toxins. Inspired by these motile microorganisms, researchers have been developing artificial particles that feature similar swimming behaviors based on different mechanisms. These man-made micromachines and nanomachines hold a great potential as autonomous agents for health care, sustainability, and security applications. With a focus on the basic physical features of the interactions of self-propelled Brownian particles with a crowded and complex environment, this comprehensive review will provide a guided tour through its basic principles, the development of artificial self-propelling microparticles and nanoparticles, and their application to the study of nonequilibrium phenomena, as well as the open challenges that the field is currently facing.
2,188 citations
Cites background from "Chemotaxis in Escherichia coli anal..."
...Various kinds of biological microswimmers exist in nature, e.g. bacteria (Berg, 2004; Berg and Brown, 1972; Berg and Turner, 1990), unicellular protozoa (Blake and Sleigh, 1974; Machemer, 1972), and spermatozoa (Riedel et al., 2005; Woolley, 2003)....
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TL;DR: The molecular mechanisms that underlie the formation of dormant persister cells are now being unravelled and are the focus of this Review.
Abstract: Several well-recognized puzzles in microbiology have remained unsolved for decades. These include latent bacterial infections, unculturable microorganisms, persister cells and biofilm multidrug tolerance. Accumulating evidence suggests that these seemingly disparate phenomena result from the ability of bacteria to enter into a dormant (non-dividing) state. The molecular mechanisms that underlie the formation of dormant persister cells are now being unravelled and are the focus of this Review.
1,823 citations
Cites background from "Chemotaxis in Escherichia coli anal..."
...The most visible case of bacterial decision-making is chemotaxis , which relies on a trial-and-error random wal...
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TL;DR: The chemotactic sensitivity of Escherichia coli approaches that of the cell of optimum design, and data on bacteriophage absorption, bacterial chemotaxis, and chemoattractant in a cellular slime mold are evaluated.
Abstract: Statistical fluctuations limit the precision with which a microorganism can, in a given time T, determine the concentration of a chemoattractant in the surrounding medium. The best a cell can do is to monitor continually the state of occupation of receptors distributed over its surface. For nearly optimum performance only a small fraction of the surface need be specifically adsorbing. The probability that a molecule that has collided with the cell will find a receptor is Ns/(Ns + pi a), if N receptors, each with a binding site of radius s, are evenly distributed over a cell of radius a. There is ample room for many indenpendent systems of specific receptors. The adsorption rate for molecules of moderate size cannot be significantly enhanced by motion of the cell or by stirring of the medium by the cell. The least fractional error attainable in the determination of a concentration c is approximately (TcaD) - 1/2, where D is diffusion constant of the attractant. The number of specific receptors needed to attain such precision is about a/s. Data on bacteriophage absorption, bacterial chemotaxis, and chemotaxis in a cellular slime mold are evaluated. The chemotactic sensitivity of Escherichia coli approaches that of the cell of optimum design.
1,795 citations
Cites background from "Chemotaxis in Escherichia coli anal..."
...(15) As long as J' is small compared with Jmax = 4wraDc....
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...These cells execute a threedimensional random walk (15)....
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...coli, Trot is typically a few seconds, somewhat longer than the length of a run (15), so the run length remains the controlling limit on gradient measurement and response time....
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TL;DR: An attempt is made to understand how cross-talk between parallel phosphotransfer pathways can provide a global regulatory curcuitry.
Abstract: Bacteria continuously adapt to changes in their environment. Responses are largely controlled by signal transduction systems that contain two central enzymatic components, a protein kinase that uses adenosine triphosphate to phosphorylate itself at a histidine residue and a response regulator that accepts phosphoryl groups from the kinase. This conserved phosphotransfer chemistry is found in a wide range of bacterial species and operates in diverse systems to provide different regulatory outputs. The histidine kinases are frequently membrane receptor proteins that respond to environmental signals and phosphorylate response regulators that control transcription. Four specific regulatory systems are discussed in detail: chemotaxis in response to attractant and repellent stimuli (Che), regulation of gene expression in response to nitrogen deprivation (Ntr), control of the expression of enzymes and transport systems that assimilate phosphorus (Pho), and regulation of outer membrane porin expression in response to osmolarity and other culture conditions (Omp). Several additional systems are also examined, including systems that control complex developmental processes such as sporulation and fruiting-body formation, systems required for virulent infections of plant or animal host tissues, and systems that regulate transport and metabolism. Finally, an attempt is made to understand how cross-talk between parallel phosphotransfer pathways can provide a global regulatory curcuitry.
1,633 citations
References
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TL;DR: These results show that E. coli is chemotactic toward oxygen and energy sources such as galactose, glucose, aspartic acid, threonine, or serine and that chemotaxis allows bacteria to find that environment which provides them with the greatest supply of energy.
Abstract: Motile Escherichia coli placed at one end of a capillary tube containing an energy source and oxygen migrate out into the tube in one or two bands, which are clearly visible to the naked eye and can also be demonstrated by photography, microscopy, and densitometry and by assaying for bacteria throughout the tube. The formation of two bands is not due to heterogeneity among the bacteria, since the bacteria in each band, when reused, will form two more bands. If an anaerobically utilizable energy source such as galactose is present in excess over the oxygen, the first band consumes all the oxygen and a part of the sugar and the second band uses the residual sugar anaerobically. On the other hand, if oxygen is present in excess over the sugar, the first band oxidizes all the sugar and leaves behind unused oxygen, and the second band uses up the residual oxygen to oxidize an endogenous energy source. The essence of the matter is that the bacteria create a gradient of oxygen or of an energy source, and then they move preferentially in the direction of the higher concentration of the chemical. As a consequence, bands of bacteria (or rings of bacteria in the case of agar plates) form and move out. These results show that E. coli is chemotactic toward oxygen and energy sources such as galactose, glucose, aspartic acid, threonine, or serine. The full repertoire of chemotactic responses by E. coli is no doubt greater than this, and a more complete list remains to be compiled. The studies reported here demonstrate that chemotaxis allows bacteria to find that environment which provides them with the greatest supply of energy. It is clearly an advantage for bacteria to be able to carry out chemotaxis, since by this means they can avoid unfavorable conditions and seek optimum surroundings. Finally, it is necessary to acknowledge the pioneering work of Englemann, Pfeffer, and the other late-19thcentury biologists who discovered chemotaxis in bacteria, and to point out that the studies reported here fully confirm the earlier reports of Beijerinck (4) and Sherris and his collaborators (5,6) on a band of bacteria chemotactic toward oxygen. By using a chemically defined medium instead of a complex broth, it has been possible to study this band more closely and to demonstrate in addition the occurrence of a second band of bacteria chemotactic toward an energy source. Beijerinck (4) did, in fact, sometimes observe a second band, but he did not offer an explanation for it.
1,116 citations
Journal Article•
TL;DR: Motile Escherichia coli placed at one end of a capillary tube containing an energy source and oxygen migrate out into the tube in one or two bands, which can also be demonstrated by photography, microscopy, and densitometry and by assaying for bacteria throughout the tube as discussed by the authors.
Abstract: Motile Escherichia coli placed at one end of a capillary tube containing an energy source and oxygen migrate out into the tube in one or two bands, which are clearly visible to the naked eye and can also be demonstrated by photography, microscopy, and densitometry and by assaying for bacteria throughout the tube. The formation of two bands is not due to heterogeneity among the bacteria, since the bacteria in each band, when reused, will form two more bands. If an anaerobically utilizable energy source such as galactose is present in excess over the oxygen, the first band consumes all the oxygen and a part of the sugar and the second band uses the residual sugar anaerobically. On the other hand, if oxygen is present in excess over the sugar, the first band oxidizes all the sugar and leaves behind unused oxygen, and the second band uses up the residual oxygen to oxidize an endogenous energy source. The essence of the matter is that the bacteria create a gradient of oxygen or of an energy source, and then they move preferentially in the direction of the higher concentration of the chemical. As a consequence, bands of bacteria (or rings of bacteria in the case of agar plates) form and move out. These results show that E. coli is chemotactic toward oxygen and energy sources such as galactose, glucose, aspartic acid, threonine, or serine. The full repertoire of chemotactic responses by E. coli is no doubt greater than this, and a more complete list remains to be compiled. The studies reported here demonstrate that chemotaxis allows bacteria to find that environment which provides them with the greatest supply of energy. It is clearly an advantage for bacteria to be able to carry out chemotaxis, since by this means they can avoid unfavorable conditions and seek optimum surroundings. Finally, it is necessary to acknowledge the pioneering work of Englemann, Pfeffer, and the other late-19thcentury biologists who discovered chemotaxis in bacteria, and to point out that the studies reported here fully confirm the earlier reports of Beijerinck (4) and Sherris and his collaborators (5,6) on a band of bacteria chemotactic toward oxygen. By using a chemically defined medium instead of a complex broth, it has been possible to study this band more closely and to demonstrate in addition the occurrence of a second band of bacteria chemotactic toward an energy source. Beijerinck (4) did, in fact, sometimes observe a second band, but he did not offer an explanation for it.
928 citations
TL;DR: In the early 1900s, it was known that motile bacteria are attracted to a variety of small organic molecules as mentioned in this paper, but few scientists were interested in bacterial chemotaxis, probably because they were unwilling to believe that these lowly organisms possessed any capability for information processing or could exhibit even simple forms of behavior.
Abstract: For a hundred years it was known that motile bacteria are attracted to a variety of small organic molecules. However, few scientists were interested in bacterial chemotaxis, probably because they were unwilling to believe that these lowly organisms possessed any capability for information processing or could exhibit even simple forms of behavior. Despite evidence to the contrary, it was generally assumed that chemotaxis and metabolism were hopelessly entwined. Bacteria simply congregated where the food was; after all, that was where growth rates were fastest. Julius Adler broke this prejudice. Undaunted by peer pressure, Adler set out to uncover the molecular basis for bacterial chemotaxis and, in particular, to test rigorously the perceived connection between this phenomenon and metabolism. First he modified a method developed by Pfeffer in the 1880s to permit a quantitative analysis of chemotaxis with Escherichia coli, an experimentally tractable organism. Basically this method involves inserting a capillary containing an attractant solution into a suspension of bacteria and then counting the cells that swim into the tube after a defined incubation period. Legend has it that he searched the sewers of Madison, Wis., to find an intelligent strain of E. coli. Domesticated strains, which are used to a life of luxury, had become either stupid or paralyzed. The paper is written in a beautifully clear, Socratic style; questions are posed and answers are provided. With this quantitative assay, Adler presented five lines of evidence demonstrating that bacteria have chemoreceptors for attractants: (i) some metabolites fail to attract, (ii) some attractants cannot be metabolized, (iii) attractants can be detected even when cells are flooded with metabolites, (iv) competition is observed with structurally related attractants, and (v) mutants defective in chemotaxis can still metabolize the molecule in question. Moreover, using attractant competition and mutant analysis, he went on to identify at least five different chemoreceptors. Appropriately enough, the paper ends with a section entitled “Implications for neurobiology and behavioral biology.” Adler's elegantly simple experiments demonstrated that bacteria such as E. coli can sense and process environmental information with surprising sophistication. Now many scientists were “attracted” to chemotaxis, and the field grew exponentially. What is remarkable is the diversity of these scientific converts. They include mathematicians and physicists, biochemists and structural biologists, geneticists and molecular biologists, and neurobiologists. Despite the fact that the components of E. coli's “brain” have been identified and analyzed in great detail, important questions remain, including the basis for the large range of ligand sensitivity and the mechanisms of signal amplification and adaptation. Because these questions are fundamental to any sensory system, it is likely that bacterial chemotaxis will remain at the forefront of this important research field. Julius Adler spawned an enormously productive enterprise. THOMAS J. SILHAVY
615 citations
TL;DR: 40 mutants of Escherichia coli which are nonchemotactic as judged by their failure to swarm on semisolidtryptone plates or to make bands in capillary tubes containing tryptone broth are isolated.
Abstract: We have isolated 40 mutants of Escherichia coli which are nonchemotactic as judged by their failure to swarm on semisolid tryptone plates or to make bands in capillary tubes containing tryptone broth. All the mutants have normal flagella, a fact shown by their shape and reaction with antiflagella serum. All are fully motile under the microscope and all are sensitive to the phage chi. Unlike its parent, one of the mutants, studied in greater detail, failed to show chemotaxis toward oxygen, glucose, serine, threonine, or aspartic acid. The failure to exhibit chemotaxis does not result from a failure to use the chemicals. The swimming of this mutant was shown to be random. The growth rate was normal under several conditions, and the growth requirements were unchanged. Images
235 citations
217 citations