Carboxypeptidase activity drives L,D-transpeptidase essentiality during vegetative growth and sporulation in Clostridioides difficile.

Carboxypeptidase activity enables Clostridioides difficile to rely on L,D-transpeptidases for peptidoglycan crosslinking, with 70% of crosslinks being 3-3 in vegetative growth.

• Why it matters: Understanding the mechanisms behind peptidoglycan crosslinking is crucial because C. difficile depends heavily on LDTs for viability, and disrupting this process could inform new antimicrobial strategies.
• What they did: The study identified D-alanyl-D-alanine carboxypeptidases DacA and DacC as sources of tetrapeptides for LDTs, and used gene deletions to reengineer crosslinking from 3-3 to 4-3, analyzing resulting phenotypes.
• The result: Deleting DacA and DacC bypassed LDT requirement and maintained viability despite reduced sporulation, revealing that high DD-CPase activity supports LDT dependence and suggesting a collaborative model of PG synthesis involving PBPs and LDTs.