Luminescent bacteria isolated from the waters of the Black Sea and of the Indian and Pacific Oceans were tested for the presence of restriction endonucleases. For 12 of 19 restriction enzyme producers revealed, restriction sites were determined. The enzymes were identified as isoschizomers of AfIII, BanI, HaeIII, PstI, Sau3AI, and Sau96I. Possible participation of the restriction and modification enzymes in the interaction of bacterial symbionts with the animal macrosymbiont is discussed.