Measurement of E. coli attractant response and intracellular information transmission achieved by the University of Osaka

A research team including Associate Professor Hajime Fukuoka and Professor Akihiko Ishijima of the Graduate School of Frontier Biosciences at the University of Osaka, has succeeded in simultaneously observing the attractant response and intracellular information transmission of a single E. coli cell. The findings were published in Science Advances.

Although E. coli is a small, single-celled organism, it controls the rotation of its flagellar motor through an information transmission system called the chemotaxis system to move toward favorable environments. Extracellular stimuli are recognized by receptors within the cell membrane, and that information is transmitted to the flagellar motor via phosphorylated response regulators, thereby controlling cell movement.

When E. coli recognizes a favorable stimulus (an attractant stimulus), it suppresses the activity of histidine kinase and the phosphorylation of response regulators, promoting counterclockwise rotation of the motor. As a result, the cell swims straight toward the attractant stimulus. It also resets the system so that it no longer reacts to an attractant stimulus it has already reacted to, allowing it to remain in a favorable environment. However, it was unclear how the enzymes responsible for information transmission behave within cells that are responding to stimuli, and how that behavior links to cellular action.

The research team fluorescently labeled the response regulator with YFP and the response regulator's phosphatase with CFP. By measuring the fluorescence resonance energy transfer (FRET) between the two proteins, they observed the changes in response regulator concentration in response to attractant stimuli and the cellular response (flagellar motor rotation) simultaneously.

As a result, they demonstrated in a single living cell that the flagellar motor responds sharply to the decrease in response regulator concentration caused by attractant stimuli and the recovery of concentration due to adaptation, and that the sensitivity of the motor to the response regulator concentration changes before stimulus reception and after stimulus adaptation. This linked the intracellular dynamics of the response regulator during the attractant response to the cell's behavior.

Fukuoka stated: "An E. coli cell is complete as a life form in a single cell. This research has enabled us to understand some aspects of cellular response behavior to chemicals as protein dynamics. In the future, I would like to aim for the elucidation of 'the principles by which the behavior of biomolecules within cells creates the behavior of organisms.' By further developing the knowledge obtained in this research, I would like to challenge ourselves to understand infection processes, such as 'how pathogenic bacteria move within a host and select infection sites,' and to create methods to suppress infection by controlling the behavioral principles of bacteria."

Journal Information
Publication: Science Advances
Title: Correlation of CheY-P concentration and motor behavior during attractant adaptation in single E. coli cells
DOI: 10.1126/sciadv.aea7305