Hi Owen, you are right that these were inactive - like a kind of suspended animation because there was so little nutrient and other essentials. But they remained alive it seems, waiting for better times. As for the deepest active microbes, there is apparently data on microbes existing deep deep within the fissures and faults of the crust and the rock beneath the ocean mantle... but I haven't seen those papers. I'll look that up - and maybe that sounds like the makings of another story - you want to take that on? If not I'll be happy to tackle that.