Three Spikous Bacterium bugs, freshly hatched, and a nest
This is a strange creature indeed. The Spikous Bacterium is not a bacteria at all, but a combination of a nest and a bug. The large spiky nests should be left alone by creatures, as they will produce an allergic reaction (a mild case of Histamine A) if pushed or hit.
The nests break apart into three Spikous Bacterium bugs, which can be eaten - curing some types of poisoning, according to the Agent Help file. However, your creatures can easily die from eating Spikous Bacterium bugs as each one consumed causes approximately 45-50% of the injury level needed to kill a Norn, Grendel or Ettin.
Spikous Bacterium are part of the ecosystem of the Terra and Terra Reborn metarooms. In Terra their nests can be found in the bottom left room near the entrance, in Terra Reborn they are on the top right room with the acorn plants.