Cyclic Di-AMP Affects Cell Membrane Integrity of Streptococcus pneumoniae

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• The bacterial second messenger cyclic di-adenosine monophosphate (c-di-AMP) is known to modulate competence in Streptococcus pneumoniae.
• A cdaA* mutant, with reduced c-di-AMP levels, unexpectedly shows susceptibility to competence-stimulating peptide (CSP).

Purpose of the Study:

• To investigate the mechanism behind the CSP susceptibility in the cdaA* Streptococcus pneumoniae strain.
• To identify genetic factors that suppress the CSP susceptibility and explore the role of c-di-AMP in cell membrane integrity.

Main Methods:

• Screening of cdaA* suppressor mutants resistant to CSP.
• Sequencing of mutated clones to identify genetic alterations.
• Analysis of gene deletions and promoter modifications related to FabT and K+ uptake.
• Assessment of c-di-AMP phosphodiesterase-null mutants' sensitivity to ethanol and Triton X-100.

Main Results:

• Mutations in the c-di-AMP phosphodiesterase Pde1 and the transcription factor FabT were identified in CSP-resistant suppressor mutants.
• Deletion of fabT, disruption of its binding site, deletion of briC, or disruption of K+ uptake rescued the growth defect of the cdaA* mutant in CSP media.
• A c-di-AMP phosphodiesterase-null mutant exhibited high sensitivity to ethanol and Triton X-100, which was ameliorated by reducing c-di-AMP levels.

Conclusions:

• c-di-AMP levels are correlated with CSP susceptibility in Streptococcus pneumoniae.
• c-di-AMP plays a significant role in maintaining cell membrane integrity, affecting sensitivity to membrane-damaging agents.
• The findings reveal a novel link between c-di-AMP signaling, cell membrane homeostasis, and bacterial competence.