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Gradius Wiki
For other uses, see Bacterian (disambiguation).

I was born... Out of the greediness of mankind. While men exist, so will I!!!
~ Bacterian in Gradius III

Bacterian (バクテリアン Bakuterian?) (also referred to as Bacterion in some early English instruction booklets) is one of the main antagonists in the Gradius series. He is known for being the most prominent enemy of the Gradians and has been responsible for most of the attacks on planet Gradius. He is the final boss in Gradius III.


It is not known where Bacterian comes from or why he wants to destroy Gradius, although it's known he came from a star cluster in Sub-Space. He's a cell that can multiply to make himself an armada of cells and ships. He usually works alone, but he once allied with Venom in an effort to defeat the Gradian forces. Gradius Gaiden's prologue revealed that he was actually the Bacterians' center of power during the Third Bacterian War. The game manual for Gradius III and IV also describes Bacterian as the "God of Destruction" and leader of the Dark Force (the final boss in Gradius III). In Gradius Galaxies, a piece of him infects a planet near Gradius and transforms it into a mechanical fortress.

Even though Bacterian is in pieces, these will regenerate in time until another Bacterian is born.

There is a running joke concerning Bacterian in that as the leader of the invading forces, he should be quite strong. On the contrary, it takes little to no effort to dispatch him. This may be explained by the difficulty of the security that the player must go through to get to Bacterian himself, thus explaining why the "boss" is so easily dispatched: the boss' protective measures were the entirety of the previous stage, not anything to do with the boss itself. In fact, since the final stage of Gradius III (SNES) is the body of Bacterian, the enemies there may be Bacterian trying to expel the player with his defense system; therefore, the entire level can be thought of as a "boss battle". The tradition of Bacterian being weak has been parodied in many ways, and even to Gradius V this trend continues.

Attack patterns

Bacterian only attacks by firing three slow-moving bolts at the player. In the arcade version, these bolts can be potentially deadly, as they fly a bit faster, and if the player is struck by one, they'll be teleported to the first stage of either Salamander or Gradius, depending on which one in the pattern hit them. It will also strip the ship from its powers. In the SNES version, however, the bolts move slower and kill on contact.

Even though Bacterian can be taken out quite quickly, after a few seconds, he will die without any need for the player to shoot him at all.



  • According to his quote at the end at the battle in the arcade version of Gradius III, Bacterian is born out of the greediness of mankind, so it is possible that the faces surrounding him are a representation of this.
  • It's possible that Bacterian may be an evolved form of the Xaerous Brain in Gradius.
Gradius III
Ships Vic Viper
Stages DesertBubble ZoneVolcanic PlanetHigh Speed DimensionMoai ZoneCell PlanetProminence PlanetPlant PlanetCrystal ZoneBoss RushMechanical Base
SNES exclusive stages High Speed ZoneFortressCell
Bosses GoliathBubble EyeGodreiBig Core MK IIIDogasVaifTwin Vaif (SNES) • GregolWyvernVulture DragonChoking WeedLizard CoreBeacon (SNES) • TetranCovered CoreBig Core MK IICrystal CoreDeath MK IIDellinger CoreDisruptShadow GearShadow Gear MK II (SNES) • Big CoreGolemBacterian
End bosses and major enemies
Major Recurring Foes GoferBacterianDr VenomZelos Force (Zeros)Lars Empire
Minor Enemies Xaerous BrainO.V.U.M.Eleos BrainMother Computer ZGuardian CoreCentral ServerGenocide CoreMetal SlaveZelos BarrierDoom