Involved in the synthesis of peptidoglycan associated with cell wall elongation, especially following spore germination (PubMed:9139922). Has a partially redundant function with PBP 1 (ponA) or PBP 4 (pbpD) during spore outgrowth (PubMed:9851991). Plays a redundant role with PbpH in determining the rod shape of the cell during vegetative growth and spore outgrowth (PubMed:12896990). Preferential cleavage: (Ac)2-L-Lys-D-Ala-|-D-Ala. Also transpeptidation of peptidyl-alanyl moieties that are N-acyl substituents of D-alanine. Cell wall biogenesis; peptidoglycan biosynthesis. Expressed in vegetative cells. Also present in dormant spores in the forespore inner membrane. Transcribed during vegetative phase, drops off during sporulation, rises again 30-40 minutes after germination. A small amount is present in dormant spores. No visible phenotype during vegetative growth rate in rich media, no difference in sporulation or initial spore germination. Spores have a significant delay in outgrowth, between 60-90 minutes cells swell rather than elongate, upon eventual elongation they have a larger diameter and are often bent (PubMed:9139922, PubMed:9851991). Single deletions have reduced peptidoglycan (PG) synthesis and turnover rates. Double ponA-pbpA deletions spores have greatly decreased viability, PG synthesis and elongate poorly; increased levels of Mg(2+) increase spore viability. Double pbpA-pbpD deletions spores have greatly decreased spore outgrowth and peptidoglycan synthesis (PubMed:9851991). Single pbpA mutants are less resistant to ceftriaxone and mecillinam. Double pbpA-pbpH mutants cannot be made, suggesting the 2 proteins have redundant, essential roles in vegetative growth (PubMed:12896990). Belongs to the transpeptidase family.