megabacterial

The story

1. Proto-Indo-European*méǵh₂s
2. Proto-Hellenic*mégas
3. Ancient Greekμέγᾰς (mégăs)
4. Englishmega-
5. Ancient Greekβακτηρία (baktēría)
6. Ancient Greekβακτήριον (baktḗrion)
7. New Latinbactēria
8. Englishbacteria
9. Proto-Indo-European*h₂el-
10. Proto-Indo-European*h₂élisder.?
11. Englishbacterial
12. English todaymegabacterial

From mega- + bacterial.