We found that DNA polymerase I from Chlamydiophila pneumoniae AR39 (CpDNApolI) presents DNA-dependent DNA polymerase activity, but has no detectable 3' exonuclease activity. CpDNApolI-dependent DNA synthesis was performed using DNA templates carrying different lesions. DNAs containing 2'-deoxyuridine (dU), 2'-deoxyinosine (dI) or 2'-deoxy-8-oxo-guanosine (8-oxo-dG) served as templates as effectively as unmodified DNAs for CpDNApolI. Furthermore, the CpDNApolI could bypass natural apurinic/apyrimidinic sites (AP sites), deoxyribose (dR), and synthetic AP site tetrahydrofuran (THF). CpDNApolI could incorporate any dNMPs opposite both of dR and THF with the preference to dAMP-residue. CpDNApolI preferentially extended primer with 3'-dAMP opposite dR during DNA synthesis, however all four primers with various 3'-end nucleosides (dA, dT, dC, and dG) opposite THF could be extended by CpDNApolI. Efficiently bypassing of AP sites by CpDNApolI was hypothetically attributed to lack of 3' exonuclease activity.