Bacteria and archaea

Bacteria and archaea inhabit soils in great numbers, with a single gram of soil often containing up to a billion individuals representing thousands of species. Although both groups are prokaryotic, bacteria and archaea possess distinctive characteristics. These organisms are crucial to soil functioning and environmental quality. Many also interact intimately with higher organisms, forming beneficial symbioses, or causing disease. This chapter provides an overview of the morphological, metabolic, and genetic diversity present within soil bacteria and archaea and introduces some of their many ecological roles vital to life on Earth. Also introduced are some common approaches used for their enumeration and characterization.