Strictly DNA-template-directed DNA polymerase, preferentially acting on DNA structures containing gaps from one to a few nucleotides and bearing a phosphate group at the 5' end of the downstream DNA. The fact that PolX is able to conduct filling of a single-nucleotide gap, allowing further sealing of the resulting nick by a DNA ligase, points to a putative role in base excision repair (BER) during the B.subtilis life cycle. Moreover, also possesses a 3'-5' exonuclease activity able to edit unpaired 3'-termini in a gapped DNA substrate and likely involved in resecting unannealed 3'-termini during DNA repair. The same PolX molecule could perform the subsequent gap-filling step. Does not display 5'-deoxyribose 5'-phosphate (dRP) lyase activity, as predicted by the lack of the lysine and tyrosine residues responsible for the dRP lyase activity in some other PolX members. a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Exonucleolytic cleavage in the 3'- to 5'-direction to yield nucleoside 5'-phosphates. Probably binds 2 divalent metal cations per N-terminal polymerase domain. Mn(2+) is more effective than Mg(2+) for DNA polymerase activity. Probably binds 3 Mn(2+) ions per C-terminal exonuclease domain. Mg(2+) cannot replace Mn(2+) for 3'-5' exonuclease activity. The polymerization activity is inhibited in the presence of 2'-3'-dideoxynucleoside 5'-triphosphate (ddNTP). Monomer. The 3'-5' exonuclease activity resides in the C-terminal PHP domain. In the N-terminal section; belongs to the DNA polymerase type-X family. In the C-terminal section; belongs to the PHP family.