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. 1972 Sep;69(9):2509–2512. doi: 10.1073/pnas.69.9.2509

The Gradient-Sensing Mechanism in Bacterial Chemotaxis

Robert M Macnab 1, D E Koshland Jr 1
PMCID: PMC426976  PMID: 4560688

Abstract

A “temporal gradient apparatus” has been developed that allows the motility of bacteria to be studied after they have been subjected to a sudden change from one uniform concentration of attractant to another. A sudden decrease elicits the tumbling response observed with spatial gradients; it was found, however, that a sudden increase also elicits a response, namely supercoordinated swimming. This demonstrates that chemotaxis is achieved by modulation of the incidence of tumbling both above and below its steady-state value. The initial responses gradually revert to the steady-state motility pattern characteristic of a uniform distribution of attractant. The apparent detection of a spatial gradient by the bacteria therefore involves an actual detection of a temporal gradient experienced as a result of movement through space. Potential models for the chemotactic response based on some “memory” mechanism are discussed.

Keywords: temporal gradient apparatus, stopped-flow, S. typhimurium, motility tracks, memory

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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