Orange enzyme bullets appear as a small glowing circle of orange goo that splatters into orange goo when it hits something. They appear in the game from fifth level onwards.
In actuality, orange enzyme bullets are the first type of orange enzyme introduced. When the orange enzyme bullet is fired, it starts off as a flash of dark orange and turns into the actual bullet, traveling in the direction it was shot. The bullet will explode once it hits a wall or Blue. It is known that the bullet will harm all other types of orange enzymes.
Blue is known to posses a blue enzyme variation of the orange enzyme bullets in his mechanical suit. The bullets are lethal to Blue and will instantly kill him on contact. Orange enzyme bullets, like everything in Test Subject Blue, will go through green teleporters if fired through, and will still maintain the same effect it always does. Orange enzyme bullets are the only used hazard ammunition in Test Subject Blue. They will also not harm lasers, as with other hazards or interactive objects.
Orange enzyme bullets appear in Test Subject Arena, fired by detection proton cannons. This is their only appearance in Test Subject Arena.
- Blue uses a reverse-engineered version of the orange enzyme bullets, firing blue enzyme bullets instead.
- The orange enzyme bullets resemble the high energy balls from the game Portal.