Use of the Scanning Electron Microscope for Viewing Bacteria in Soil

Scanning electron microscopy was used for viewingBacillus cereus andStaphylococcus aureus in three different soils. Both organisms were detected in the test soils at an approximate concentration of 107 cells per gram of soil; theoretically, the minimal number of microorganisms required for detection with the scanning electron microscope technique was between 107 and 1010 cells per gram of soil. Because the concentration of cells was critical, the use of scanning electron microscopy as an extraterrestrial life detection instrument would be limited with soils containing more than 107 bacteria per gram of soil.