Intact and mutated Shigella diguanylate cyclases increase c-di-GMP

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Shigella flexneri is an intracellular pathogen causing colonic epithelial disease.
• Bacterial adaptation to diverse environments relies on signaling systems like cyclic di-GMP (c-di-GMP).
• Diguanylate cyclases (DGCs) with GGDEF domains synthesize c-di-GMP.

Purpose of the Study:

• To investigate the roles of individual S. flexneri DGCs in c-di-GMP synthesis.
• To determine the contribution of DGCs to Shigella pathogenesis and adaptation.
• To explore the function of degenerate DGC pseudogenes in c-di-GMP signaling.

Main Methods:

• Individual expression of four intact S. flexneri DGCs in a Δ4DGC mutant strain.
• In vitro and in vivo assessment of c-di-GMP synthesis by DGCs.
• Phenotypic analysis of Shigella invasion, plaque formation, and acid sensitivity.

Main Results:

• Four intact S. flexneri DGCs synthesize c-di-GMP at varying levels.
• dgcF and dgcI expression reduced invasion and plaque formation, with dgcF increasing acid sensitivity.
• Degenerate DGCs (dgcE, dgcQ, dgcN) with mutations still produce c-di-GMP, expressed as multiple proteins.

Conclusions:

• Both intact and degenerate DGCs contribute to S. flexneri c-di-GMP signaling.
• The study highlights the complex role of DGCs in bacterial adaptation and pathogenesis.
• Degenerate DGCs represent a novel source of c-di-GMP in S. flexneri.