Excitatory signaling in bacterial probed by caged chemoeffectors

Area of Science:

• Microbiology and Molecular Biology
• Cellular Signaling and Motility

Background:

• Bacterial chemotaxis is a fundamental process for cell navigation and survival.
• Understanding the kinetics of bacterial signal processing requires precise control over stimuli.
• Previous studies lacked methods for rapid, localized introduction of chemoattractants and repellents.

Purpose of the Study:

• To investigate chemotactic excitation responses in bacteria using computer-assisted measurements.
• To analyze signal processing times and pathway kinetics in intact bacteria, including mutants.
• To synthesize and utilize novel caged ligands for controlled photorelease of serine and protons.

Main Methods:

• Synthesis of 'caged' serine and 'caged' proton compounds for flash photolysis.
• Computer-aided measurement of bacterial (Vibrio alginolyticus, Escherichia coli, Salmonella typhimurium) responses to photoreleased ligands.
• Utilized receptor deletion and motility mutants to dissect signaling and motor response pathways.

Main Results:

• Photorelease of caged serine and protons generated rapid attractant and repellent signals.
• Bacterial responses occurred with minimal latency, and response times correlated with stimulus strength.
• Motility mutants showed altered sensitivity but largely normal response times, implicating CheY phosphorylation as a key regulator.

Conclusions:

• Bacterial chemotaxis signaling is rapid and robust, with signal processing times largely independent of motility behavior.
• The phosphorylated CheY protein is a critical determinant of motor response to both attractant and repellent stimuli.
• Control of CheY phosphate concentration, rather than motor reactions, appears to limit chemotactic responses.