Subatomic bacteria were a type of bacteria that were found feeding on the tritanium plating of the IKS Pagh's hull.
Following their discovery, Klingon Captain Kargan believed they were part of a Federation plot. However, the subatomic bacteria were also discovered on the hull of the USS Enterprise-D by Mendon.
They were safely removed from both vessels via the use of a tunneling neutrino beam. (TNG: "A Matter Of Honor")