Catalyzes efficient strand joining on a single nicked DNA. ATP + (deoxyribonucleotide)n-3'-hydroxyl + 5'-phospho-(deoxyribonucleotide)m = (deoxyribonucleotide)n+m + AMP + diphosphate. Belongs to the ATP-dependent DNA ligase family. Was originally proposed to code for two separate adjacent ORFs, HI_1182 and HI_1183.