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A Method for Measuring Chemotaxis and Use of the Method to Determine Optimum Conditions for Chemotaxis by Escherichia coli
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1973
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BacteriologyEscherichia ColiMicrobial PhysiologyMeasuring ChemotaxisAnaerobic CulturingBioenergeticsMicrobial EcologyEnvironmental MicrobiologyInfection ControlAntimicrobial ResistanceAerobic CulturingDetermine Optimum ConditionsHealth SciencesBiochemistryCapillary OpeningCapillary TubeAntimicrobial SusceptibilityMicrobiologyMedicineQuantitative Microbiology
Chemotaxis of *Escherichia coli* is measured by counting bacteria that enter a capillary tube containing an attractant. The assay examines how capillary volume, opening size, and chemical concentration gradients affect bacterial accumulation. Bacterial accumulation follows a concentration‑response curve to l‑aspartate, depends on cell density, requires EDTA and neutral pH, can be enhanced by K⁺, and increases 20‑fold when temperature rises from 20 to 30 °C.
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.