Geoscience Reference
In-Depth Information
Fig. 4.1
Soil bacteria
Each of the many steps of decomposition of organic molecules is produced by
different specifi c families of bacteria, all of which are known as chemotrophs that
derive their energy from chemical reactions. Chemical reactions (known as an oxi-
dation process) under aerobic conditions are often 10 times faster than those (known
as a reduction process) under anaerobic conditions. Bacteria are active in many
oxidation and reduction processes in soils. Speaking in a very simplifi ed chemical
language, oxidation occurs when the outside shell of an atom loses an electron and
reduction occurs when the outside shell of an atom gains an electron. Bivalent iron
compounds are changed to compounds containing trivalent iron during oxidation. In
other words, the number of electrons missing in each atom of iron increased from
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