Toxic component of the hybrid type II/IV toxin-antitoxin (TA) system DarTG, which plays a crucial role in controlling bacterial growth and bacteriophage infection. Its toxic effect is neutralized by cognate antitoxin DarG. In case of phage infection, DarT toxin ADP-ribosylates DNA, which inhibits both viral DNA and RNA synthesis and leads to abortive infection. ADP-ribosylates ssDNA on the second thymidine of the consensus sequence 5'-TNTC-3'; the protein does not auto-modify. Has no activity on dsDNA in vitro. This leads to a decrease in DNA replication. Upon expression in E.coli inhibits cell growth, colony formation and induces the SOS response. Expression leads to bacteriostasis; however if cells grow over an hour in the presence of toxin, growth is no longer restored on antitoxin-inducing plates. In E.coli ADP-ribosylates genomic DNA (gDNA), which induces RecA expression (a marker for DNA damage)