Characterization of chemotaxis and motility response towards fructose in Escherichia coli

Abstract

BackgroundPeritrichously flagellated bacteria such as Escherichia coli perform chemotaxis by a biased random walk toward various chemicals, which was driven by the bacterial flagellar motor. The chemotaxis system is a perfect robust system which can adapt to its pre-stimulus level after the stimulus. Fructose, a typical monosaccharide that can attract Escherichia coli. Previous studies have shown Escherichia coli to be chemotactic to both amino acids and simple sugars. However, little is known about the chemotaxis and motility response of Escherichia coli towards fructose.ResultsIn this study, we characterized the chemotaxis behavior of Escherichia coli to different concentrations of fructose from 0mM to 50mM by using microfluidics and bead assay. We observed the wild-type cells responded to the stimulus of fructose, which suggested fructose is an attractant to Escherichia coli, while the cells defective in chemotaxis could not sense the stimulus of fructose. Fructose affects the motor behavior of wild-type cells and reduces the CCW motor speeds significantly compared to CW motor speeds, contrast to that fructose cannot affect the motor speeds of cells defective in chemotaxis. The CW biases of wild-type cells increased with the addition of fructose. And the fructose promotes bacterial aggregation on surface by lowering the bacteria motor speed.ConclusionsWe found that fructose is an attractant to Escherichia coli, with the wild-type cells showed stronger response to higher concentration of fructose, while cells lacking chemoreceptors and CheY cannot sense or respond to fructose. The motility of wild-type cells was reduced in various concentrations of fructose, which helped the aggregation of cells near the surface, in contrast with the result that the fructose showed no effect on the motility of the cells defective in chemotaxis. Similar phenomena are expected to be found in the effect of other monosaccharides to Escherichia coli.