Many hydrocarbon-contaminated environments
are characterized by low or elevated temperatures, acidic
or alkaline pH, high salt concentrations, or high pressure.
Hydrocarbon-degrading microorganisms, adapted to
grow and thrive in these environments, play an important
role in the biological treatment of polluted extreme habitats.
The biodegradation (transformation or mineralization)
of a wide range of hydrocarbons, including aliphatic,
aromatic, halogenated and nitrated compounds, has
been shown to occur in various extreme habitats. The
biodegradation of many components of petroleum hydrocarbons
has been reported in a variety of terrestrial and
marine cold ecosystems. Cold-adapted hydrocarbon degraders
are also useful for wastewater treatment. The use
of thermophiles for biodegradation of hydrocarbons with
low water solubility is of interest, as solubility and thus
bioavailability, are enhanced at elevated temperatures.
Thermophiles, predominantly bacilli, possess a substantial
potential for the degradation of environmental pollutants,
including all major classes. Indigenous thermophilic
hydrocarbon degraders are of special significance
for the bioremediation of oil-polluted desert soil. Some
studies have investigated composting as a bioremediation
process. Hydrocarbon biodegradation in the presence
of high salt concentrations is of interest for the bioremediation
of oil-polluted salt marshes and industrial
wastewaters, contaminated with aromatic hydrocarbons
or with chlorinated hydrocarbons. Our knowledge of the
biodegradation potential of acidophilic, alkaliphilic, or
barophilic microorganisms is limited.