Catalyzes the hydrolysis of supercoiled double and single strand DNA and RNA. Involved in chromosomal DNA degradation and cell death caused by thermal stress. Binds 1 Ca(2+) ion per subunit. Can also use Co(2+) or Mn(2+). Inhibited by aurintricalboxylic acid but not by Zn(2+), Mn(2+), Hg(2+), 2-mercaptoethanol and sodium citrate. Neither inhibited nor activated by ATP. Optimum pH is 7.0-8.0. Optimum temperature is 40-45 degrees Celsius. Cells lacking this gene are more sensitive to mitomycin C, show an increased ability of competence and are not able to metabolize extracellular DNA.