Nucleogenic cloud being

From Memory Alpha, the free Star Trek reference.

The nucleogenic cloud being is a nebula-like lifeform native to the Delta Quadrant. The lifeform measured 7 AUs in diameter and was made of hydrogen, helium, and hydroxyl radicals. The being uses multi-polar charges for defense.

While looking for omicron particles in 2371, the USS Voyager harmed a species of the creature by entering its body, not knowing that it was a living entity. It eventually was able to heal itself with assistance of Voyager, which performed a 'suture' with power flow. (VOY: "The Cloud")