DNA polymerase III is a complex, multichain enzyme responsible for most of the replicative DNA synthesis in bacteria as well as the bulk of DNA synthesis/repair after ionizing radiation (IR) (PubMed:19303848). The alpha chain is the catalytic subunit (PubMed:19303848). Following severe irradiation (7 kGy of gamma irradiation) genomic DNA is fragmented. DNA is progressively degraded for the first 1.5 hours after IR, in a step promoted by RecA and counterbalanced by DNA Pol I and Pol III, followed by massive DNA synthesis and genome reassembly in the next hour. Optimal priming of DNA synthesis requires both RecA and RadA, Pol III initiates DNA synthesis while both Pol I and Pol III are required for its contination (PubMed:19303848). This DNA polymerase also exhibits 3' to 5' exonuclease activity (By similarity). a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) DNA polymerase III contains a core (composed of alpha, epsilon and theta chains) that associates with a tau subunit. This core dimerizes to form the PolIII' complex. PolIII' associates with the gamma complex (composed of gamma, delta, delta', psi and chi chains) and with the beta chain to form the complete DNA polymerase III complex (By similarity). Essential, it cannot be deleted. Belongs to the DNA polymerase type-C family. DnaE subfamily.