Deinococcus–Thermus

Deinococcus–Thermus is a phylum of extremophile bacteria that are highly resistant to environmental hazards.
These bacteria have thick cell walls that give them gram-positive stains, and they have a second membrane. They are are closer in structure to that of gram-negative bacteria.
Cavalier-Smith calls this clade Hadobacteria (from Hades, the Greek underworld).