Abstract
It is well known that Escherichia coli achieves chemotaxis by modulating the bias of the flagellar motor. Recent experiments have shown that the bacteria vary their swimming speeds as well in presence of attractants. However, this increase in the swimming speed in response to the attractants has not been correlated with the increase in the flagellar motor speed. Using flickering dark-field microscopy, we measure the head-rotation speed of a large population of cells to correlate it with the flagellar motor speed. Experiments performed with wild-type and trg-deletion mutant strains suggest that the cells are capable of modulating the flagellar motor speed via mere sensing of a ligand. The motor speed can be further correlated with the swimming speed of the cells and was found to be linear. These results suggest the existence of a hitherto unknown intra-cellular pathway that modulates the flagellar motor speed in response to sensing of chemicals, thereby making chemotaxis more efficient than previously known.
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Acknowledgments
The authors acknowledge financial support from the Department of Science and Technology, India (SB/S3/CE/089/2013) and Department of Biotechnology, India (BT/PR7712/BRB/10/1229/2013). MST also acknowledges support from the Swaranajayanti Fellowship (DST/SJF/ETA-01/2010-11).
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Communicated by Reinhard Krämer.
Richa Karmakar and Farha Naaz have contributed equally to this work.
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Karmakar, R., Naaz, F., Tirumkudulu, M.S. et al. Escherichia coli modulates its motor speed on sensing an attractant. Arch Microbiol 198, 827–833 (2016). https://doi.org/10.1007/s00203-016-1255-z
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DOI: https://doi.org/10.1007/s00203-016-1255-z