Microbial Action on Organic Matter in the Hydrosphere

An environmentally important function of microorganisms in the hydrosphere is detoxication (also called detoxification) and degradation of water contaminants, discussed further in Sections 3.12 through 3.15. The complete biodegradation of water pollutants is often the result of several kinds of microorganisms acting in sequence. For example. Micrococcus, Pseudmonas, Mycobacterium, and Nocardia may all be involved in the biodegradation of petroleum. 

The main mechanism for the biodegradation of water pollutants is oxidation, which is shown in a general sense in Reaction 3.4. For example, bacteria act on octane, an ingredient of gasoline  

This is an overall reaction that results in the conversion of the hydrocarbon completely to the simple inorganic compounds carbon dioxide and water, a process of mineralization. The partial oxidation of organic pollutants to intermediate organic compounds also commonly occurs. 

Microbially mediated processes other than oxidation may also occur with water pollutants. In anoxic regions of water where O2 is absent, reduction may take place. One of the most common biochemical processes mediated by microorganisms and operating on pollutants in water is hydrolysis in which a molecule is split in two with the addition of a water molecule. The products of hydrolysis are often more amenable to further biodegradation, such as oxidation, than is the parent compound. 

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