Extremophile bacteria and archea are living very deep beyond our imaginations. This is what you need for general composition at different depths. And this and this is for the deepest living organism known ! Following is image from (Manson et al 2010) which shows at what depth you will get bacteria

Even more deeper, Wold's single species ecosystem, Desulforudis audaxviator which can be found 3 km below sea level.

Full references mentioned : Mason OU, Nakagawa T, Rosner M, Van Nostrand JD, Zhou J, Maruyama A, Fisk MR, Giovannoni SJ. First investigation of the microbiology of the deepest layer of ocean crust. PLoS One. 2010 Nov 5;5(11):e15399

Extremophile bacteria and archea are living very deep beyond our imaginations. This is what you need for general composition at different depths. And this and this is for the deepest living organism known ! Following is image from (Manson et al 2010) which shows at what depth you will get bacteria

Even more deeper, Wold's single species ecosystem, Desulforudis audaxviator which can be found 3 km below sea level.