There are more microbes in 1 teaspoon of soil than there are people on earth.
F"There are more microbes in a teaspoon of soil than there are people on the earth." (page 1; also see Table 1)James J. Hoorman and Rafiq Islam, “Understanding soil microbes and nutrient recycling,” Ohio State University Extension, 2010, 1, accessed May 27, 2015, http://ohioline.osu.edu/sag-fact/pdf/0016.pdf.