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Journal ArticleDOI

A method for measuring chemotaxis and use of the method to determine optimum conditions for chemotaxis by Escherichia coli.

01 Jan 1973-Microbiology (Microbiology Society)-Vol. 74, Iss: 1, pp 77-91
TL;DR: Rate of bacterial accumulation in capillaries and a concentration-response curve for l-aspartate taxis are presented and interpreted, and the effect of bacterial concentration is reported.
Abstract: SUMMARY: Chemotaxis of a bacterium such as Escherichia coli is assayed by measuring the number of organisms attracted into a capillary tube containing an attractant. Rate of bacterial accumulation in capillaries and a concentration-response curve for l-aspartate taxis are presented and interpreted, and the effect of bacterial concentration is reported. Other parameters of the assay were studied, such as the volume of fluid in the capillary and the size of the capillary opening. The concentration gradient of chemical was also described. Escherichia coli chemotaxis requires EDTA to allow motility, a buffer to maintain the pH at its optimum near neutrality, and l-methionine if it cannot be synthesized. Under certain conditions there is stimulation by inorganic ions, either by K+ or, less effectively, by Na+. Chemotaxis is dependent on temperature, there being a 20-fold increase in the number of bacteria accumulating in a capillary when the temperature is raised from 20 to 30 °C.
Citations
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Journal ArticleDOI
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.

1,795 citations

Journal ArticleDOI
TL;DR: The conclusion is offered that interactions between microspikes and the substratum adjacent to the growth cone are important determinants of the directions and pathways of axonal elongation.

683 citations


Cites background from "A method for measuring chemotaxis a..."

  • ...Chemotaxis is another guiding force in cell movements (Adler, 1973; Bonner, 1947)....

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Journal ArticleDOI
03 May 1974-Nature
TL;DR: It is found that changes in the direction of flagellar rotation indeed constitute the basis of chemotaxis: addition of attractants causes counter clockwise (CCW) rotation, whereas repellents causeClockwise (CW) rotation.
Abstract: BERG and Anderson1 recently argued from existing evidence that bacteria swim by rotation of their helical flagella. Silver-man and Simon2 have now provided a clear demonstration of this. By means of antibodies specific for flagellar components, they tethered cells to microscope slides or to each other and observed rotation of the cell bodies. The cells were able to stop and to rotate in either direction. It seemed possible, as they proposed2, that cessation, or reversal of flagellar rotation might be involved in bacterial chemotaxis. Accordingly, we used wild-type and chemotaxis-defective mutant cells of Escherichia coli tethered to microscope slides in a manner similar to that of Silverman and Simon2, and stimulated them by sudden increases of chemotactic agents. We found that changes in the direction of flagellar rotation indeed constitute the basis of chemotaxis: addition of attractants causes counter clockwise (CCW) rotation, whereas repellents cause clockwise (CW) rotation.

440 citations

Journal ArticleDOI
TL;DR: The current knowledge of routes to functional diversity and DNA binding specificity is presented, including divergent properties of the conserved ETS and PNT domains, the involvement of flanking structured and unstructured regions appended to these dynamic domains, posttranslational modifications, and protein partnerships with other DNA-binding proteins and coregulators.
Abstract: ETS proteins are a group of evolutionarily related, DNA-binding transcriptional factors. These proteins direct gene expression in diverse normal and disease states by binding to specific promoters and enhancers and facilitating assembly of other components of the transcriptional machinery. The highly conserved DNA-binding ETS domain defines the family and is responsible for specific recognition of a common sequence motif, 5 � -GGA(A/T)-3 � . Attaining specificity for biological regulation in such a family is thus a conundrum. We present the current knowledge of routes to functional diversity and DNA binding specificity, including divergent properties of the conserved ETS and PNT domains, the involvement of flanking structured and unstructured regions appended to these dynamic domains, posttranslational modifications, and protein partnerships with other DNA-binding proteins and coregulators. The review emphasizes recent advances from biochemical and biophysical approaches, as well as insights from genomic studies that detect ETSfactor occupancy in living cells.

434 citations


Cites methods from "A method for measuring chemotaxis a..."

  • ...Then I needed to devise an objective assay for chemotaxis (15)....

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  • ...In this assay for chemotaxis (15), the number of bacteria attracted inside the capillary was measured (Figure 3)....

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Journal ArticleDOI
TL;DR: The present review will restrict itself to the recent work on chemotaxis in Escherichia coli and Salmonella typhimurium.
Abstract: Bacterial chemotaxis, the movement of motile bacteria toward or away from chemicals, was discovered nearly a century ago by Engelmann (43) and Pfeffer (70, 71) The subject was actively studied for about fifty years, but then there were very few reports until quite recently For reviews of the literature up to about 1960, see Berg (23) , Weibull (90) and Ziegler (92) The present review will restrict itself to the recent work on chemotaxis in Escherichia coli and Salmonella typhimurium, some of which is also covered in Berg’s review (23)

406 citations

References
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Journal ArticleDOI
27 Oct 1972-Nature
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.

2,069 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

Journal ArticleDOI
26 Dec 1969-Science
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

Journal ArticleDOI
TL;DR: A chemically defined growth medium capable of producing motile bacteria was devised and it was found that the presence of glucose or growth above 37° prevented synthesis of flagella.
Abstract: SUMMARY: A simple chemically defined medium for examining the motility of Escherichia coli K12 was designed. The essential components were: (1) a chelating agent to protect the motility against inhibition by traces of heavy metal ions; (2) a buffer to keep the pH value at the optimum between pH 6·0 and 7·5; (3) an energy source to stimulate the motility above that allowed by an endogenous energy source. Oxygen was required unless an energy source was provided which yielded energy anaerobically. A temperature optimum was determined. A chemically defined growth medium capable of producing motile bacteria was devised. It was found that the presence of glucose or growth above 37° prevented synthesis of flagella.

399 citations

Journal ArticleDOI
TL;DR: A double mutant of Escherichia coli unable to synthesize or degrade unsaturated fatty acids can incorporate fatty acids with various hydrocarbon chain structures into the membrane phospholipids, suggesting a liquid-like state of the lipid phase is required for proper membrane function.
Abstract: A double mutant of Escherichia coli unable to synthesize or degrade unsaturated fatty acids can incorporate fatty acids with various hydrocarbon chain structures into the membrane phospholipids. The temperature characteristic of three physiological properties of cells grown with different fatty acids (growth, respiration, and efflux of thiomethylgalactoside) is compared with the physical properties of the isolated phosphatidylethanolamines in monolayers at an air-water interface. Breaks in the temperature characteristic of the properties measured in vivo correspond to phase transitions in the lipid films from a liquid-expanded to a condensed form. It is concluded that a liquid-like state of the lipid phase is required for proper membrane function.

282 citations