Quantification of high-specificity cyclic diguanylate signaling

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Physiology

Background:

• Cyclic di-GMP (c-di-GMP) is a crucial second messenger regulating bacterial lifestyles.
• Bacteria possess multiple enzymes (diguanylate cyclases and phosphodiesterases) that control c-di-GMP levels.
• The specificity of c-di-GMP signaling, whether high or low, remains debated.

Purpose of the Study:

• To investigate whether c-di-GMP signaling in Vibrio cholerae operates via a high or low specificity mechanism.
• To correlate intracellular c-di-GMP concentrations with specific bacterial responses.

Main Methods:

• Vibrio cholerae strains were engineered to express seven different diguanylate cyclases at eight distinct levels.
• In vivo c-di-GMP concentrations were measured.
• Biofilm formation and gene transcription were quantified to assess c-di-GMP-mediated responses.

Main Results:

• No overall correlation was found between total intracellular c-di-GMP levels and biofilm formation or gene expression.
• Significant correlations were observed between the c-di-GMP production of individual diguanylate cyclases and specific downstream responses.
• Different diguanylate cyclases exhibited distinct rates of phenotypic change relative to c-di-GMP concentration.

Conclusions:

• Vibrio cholerae's c-di-GMP signaling network does not function as a simple, low-specificity system.
• Specific diguanylate cyclases, rather than the global c-di-GMP pool, are key regulators of bacterial phenotypes.
• Bacteria can precisely tune phenotypic outcomes by controlling the expression or activation of specific diguanylate cyclases.