Bacterian is the main enemy of the Gradians and has been responsible for most of the attacks on Gradius. It is not known where he comes from or why he wants to destroy Gradius although it's known he came from a star cluster in Sub-Space. He is a cell that can multiply to make himself an armada of cells and ships. He usually works alone, but once he 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 (Gradius III). The game manual for Gradius III & 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 that particular planet into a mechanical fortress.

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 of him. This may be explained by the difficulty of the security that the player must go through to get to Bacterian, 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. However, 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.

Although Bacterian's in pieces, these pieces will rengerate until another Bacterian is reborn.

Attack Pattern

Bacterian attacks by just firing three bolts at the player. Nothing else. In the arcade version, these bolts could be potentially deadly, as they fly a bit faster, and when you're struck by one, you go to the first stage of either Salamander or Gradius, depending on which one in the pattern you hit. It will also strip you of your powers. In the SNES version, however, the bolts move slower and kill on contact. Bacterian can be taken out extremely quickly, not just from your shots, but the fact that his health drains, meaning you can kill him without even firing a single shot.

Appears In


  • The Bacterians usually have the form of a giant brain. While in the Contra series (also by Konami), one of the most traditional bosses in the game franchise is a giant heart, in the first Contra game, it is actually the last boss, as well as the first Gradius game, which the last boss is a giant brain.
  • Those faces surrounding Bacterian may either be Bacterians or they are the many faces Bacterian can change into.
  • It's possible that Bacterian may be an evolved form of the Brain in Gradius 1.
Gradius III
Ships Vic Viper
Stages Sand StormAqua IllusionIn The WindHigh Speed DimensionEaster StoneDead End CellFire ScrambleCosmo PlantAccident Road (SNES exclusive)Crystal LabyrinthBoss RushMechanical BaseUnpleasant Cell (SNES exclusive)
Bosses GoliathBubble EyeIron MaidenBig Core MK IIIDogasVaifTwin Vaif (SNES) • GregolWyvernVulture DragonChoking WeedLizard CoreBeacon (SNES) • Zub Rush MK IITetranCovered CoreBig Core MK IICrystal CoreDeath MK IIDellinger CoreDisruptShadow GearShadow Dancer (SNES) • Big CoreBrain GolemBacterion
End Bosses & Major Enemies
Major Recurring Foes GoferBacterionDr VenomZelos Force (Zeros)Lars EmpireGofer Sisters
Minor Enemies BrainO.V.U.M.Eleos BrainMother Computer Z Guardian CoreCentral Server Genocide CoreOuter Limits / Metal SlaveZelos BarrierDoomDark Force

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