Bacteria and fungi are an important part of soils. It's part of the reason that there are culture solutions you can purchase for gardens. Mycorrhiza for exampl

Bacteria and fungi are an important part of soils. It's part of the reason that there are culture solutions you can purchase for gardens. Mycorrhiza for example is very important for the growth of certain types of herbs and vegetables (and really just a large number of plants in general). Likewise bacteria are one of the major legs of one of the major ecological processes that's essential for sustaining life on Earth (the nitrogen cycle). The bacteria in soil convert nitrogen gas from the air (which breathes into the soil) into various nitrate compounds which are then absorbed by plants' roots (this is why fertilizer often contains ammonium nitrate). Bacteria are also involved in the phosphorus cycle as well however to a lesser degree. Really micro-organisms in the soil are involved in varying degrees for each of the biogeochemical cycles that life on earth depend on.