A Method for Measuring Chemotaxis and Use of the Method to Determine Optimum Conditions for Chemotaxis by Escherichia coli

Adler, Julius

doi:10.1099/00221287-74-1-77

Cited by 765 publications

(500 citation statements)

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“…The continuous-flow capillary assay is based on the traditional quantitative capillary assay developed by Adler (2,3) and modifications thereof (7,38,51,53). In the traditional assay, a capillary filled with chemoattractant dissolved in buffer is placed into a pool of bacteria.…”

Section: Discussionmentioning

confidence: 99%

“…The continuous-flow capillary assay is a modification of the traditional capillary assay (2,3). Instead of a capillary placed into a stagnant pool of bacteria, a bacterial suspension flows past the open end of a capillary that is perpendicular to the flow path.…”

Section: Methodsmentioning

confidence: 99%

“…Methods in which metabolism can be minimized are the traditional capillary assay (2,3) and modifications thereof (7,38,51,53). Metabolism is minimized because a low cell concentration can be used, mainly due to the sensitive nature of enumerating cell accumulations in the capillaries.…”

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Continuous-Flow Capillary Assay for Measuring Bacterial Chemotaxis

Law

Aitken

2005

Appl Environ Microbiol

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Bacterial chemotaxis may have a significant impact on the structure and function of bacterial communities. Quantification of chemotactic motion is necessary to identify chemoeffectors and to determine the bacterial transport parameters used in predictive models of chemotaxis. When the chemotactic bacteria consume the chemoeffector, the chemoeffector gradient to which the bacteria respond may be significantly perturbed by the consumption. Therefore, consumption of the chemoeffector can confound chemotaxis measurements if it is not accounted for. Current methods of quantifying chemotaxis use bacterial concentrations that are too high to preclude chemoeffector consumption or involve ill-defined conditions that make quantifying chemotaxis difficult. We developed a method of quantifying bacterial chemotaxis at low cell concentrations (ϳ10 5 CFU/ml), so metabolism of the chemoeffector is minimized. The method facilitates quantification of bacterial-transport parameters by providing well-defined boundary conditions and can be used with volatile and semivolatile chemoeffectors.Chemotaxis, the self-directed movement of an organism or cell toward or away from a chemical (chemoeffector) along a concentration gradient, is a well-known bacterial behavior (1,5,6,12). The interest in bacterial chemotaxis is broad. Knowledge is sought of how the bacteria sense chemicals (4, 21-23), how chemotaxis affects pathogenesis and symbiosis (10,29,57), the role of chemotaxis in the formation and structure of bacterial communities (70), the influence of chemotaxis on oceanic nutrient cycling (8,9,17,75), and the effect of chemotaxis on pollutant biodegradation (43,52,(54)(55)(56).The chemoeffectors to which bacteria are attracted (chemoattractants) are often nutrients that the bacteria consume. Many methods for quantifying chemotactic transport use bacterial concentrations that are high enough that significant consumption of the chemoattractant occurs, affecting the chemoattractant gradient that forms. For example, Marx and Aitken (49) reported diminished chemotaxis at bacterial concentrations of Ն10 6 CFU per ml, which was believed to be a result of significant consumption of the chemoattractant (naphthalene). Therefore, complexity is introduced when interpreting measurements of bacterial migration by chemotaxis because consumption of the chemoeffector must be accounted for. Furthermore, bacterial accumulation by chemotaxis and consumption of a chemoattractant may create a secondary gradient that the bacteria also sense. For example, aerobic biodegradation of a chemoattractant by bacteria that are also aerotactic (responsive to oxygen) could create an oxygen gradient that influences bacterial migration, confounding measurements of movement toward the primary chemoattractant. Methods that are used to quantify chemotaxis, therefore, should minimize metabolism of a biodegradable chemoeffector so that the observed bacterial motion would be in response only to diffusion of the primary chemoeffector.Methods in which metabolism can be minimized...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Continuous-Flow Capillary Assay for Measuring Bacterial Chemotaxis

Law

Aitken

2005

Appl Environ Microbiol

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“…Two examples are the stopped flow diffusion chamber (SFDC) assay [19][20][21][22] and the capillary assay [1]. Both systems consist of a step-like chemoattractant concentration profile as the initial condition.…”

Section: Examplementioning

confidence: 99%

“…In particular, Rivero et al [33] demonstrated that the individual cellular properties in the Segel's 1-D model could be incorporated into the macroscopic transport parameters. A number of experimental systems (e.g., the capillary assay [1], the stopped-flow diffusion chamber [19,20], and the Boyden chamber [6]) have been designed to generate an attractant concentration gradient in one spatial dimension. Although the measurable macroscopic variable (e.g., the spatial local cell density) in those systems only varies one-dimensionally, microscopically, cells swim freely in 3-D space.…”

Section: Introductionmentioning

confidence: 99%