O-negative was a Human blood type.
This blood type was one of the three remaining blood types (the others being B-negative and AB-positive) Loomis was required to get for Damron in order for the Xindi-Reptilian to synthesize a virus for their bio-weapon, which required samples of all eight types of Human blood to be properly calibrated. Detroit prostitute Georgia Tandy had a blood type of O-negative. After Damron delivered Tandy, he requested to be paid his bounty, but was told he wouldn't be paid until they received that remaining two blood types. (ENT: "Carpenter Street")
After being changed into a Solid, specifically a Human, by the Great Link in 2372, Doctor Julian Bashir noted that Odo's blood type was O-negative. (DS9: "Broken Link")
| Blood types |
|---|
| AB-positive • B-negative • O-negative • T-negative |