Pneumococcal Competence Coordination Relies on a Cell-Contact Sensing Mechanism

Area of Science:

• Microbiology
• Bacterial genetics
• Cellular communication

Background:

• Bacteria utilize inducible genetic programs to survive stress.
• Competence enables genetic transformation, a key horizontal gene transfer process.
• Streptococcus pneumoniae exhibits synchronized competence development, dependent on Competence Stimulating Peptide (CSP).

Purpose of the Study:

• To elucidate the coordination mechanism of CSP-dependent population-wide competence switch in Streptococcus pneumoniae.
• To investigate the role of cell-cell contact in competence development.

Main Methods:

• Real-time monitoring of spontaneous competence development in four pneumococcal lineages.
• Co-cultivation experiments with strains having altered CSP production or response.
• Measurement of Competence Stimulating Peptide (CSP) binding to cells and its diffusion.

Main Results:

• Competence shift relies on a self-activated cell fraction, arising through a growth time-dependent mechanism.
• CSP remains cell-bound during competence development, propagating via cell-cell contact.
• The membrane protein ComD retains CSP, limiting its diffusion.

Conclusions:

• Competence development is coordinated by a two-step cell-contact sensing mechanism.
• Competence initiator cells arise stochastically and transmit CSP through direct cell-cell contact.
• This mechanism ensures synchronized competence development within the bacterial population.