During the past two years we have established that thermophilic bacteria belonging to the genus Geobacillus exist in large numbers in otherwise cool soil environments. These thermophiles have a growth range of 40–80°C and can be found in soils in high numbers (104 colony forming units (CFU)/g). These thermophilic geobacilli have a rapid growth rate with doubling times between 20–30 minutes at 65–70°C on nutrient broth and most have a wide rang ability to degrade hydrocarbons including aromatic molecules. This suggested that they could play a role in the attenuation of hydrocarbon-contaminated soils. To assess their activity in situ, molecular biology techniques were employed firstly though designing a taxon specific forward PCR primer (THERM) to detect the geobacilli and secondly through targeting the alkane monooxygenase (alkB) gene expression. A reverse transcriptase PCR experiment established that the alkane monooxygenase activity in pure cultures of Geobacillus are only inducible when they are grown at temperatures >40°C in the presence of alkane. Similarly soil microcosms spiked with alkane only gave the alkB RT PCR product when incubated at temperatures above 40°C. Mixed sequences of the alkB gene fragment were detected in soil and appear to belong to numerous thermophilic rather than mesophilic bacteria. We believe these thermophilic geobacilli may have a significant role in hydrocarbon biodegradation at elevated temperatures and may be utilized for bioremediation of hydrocarbon-contaminated soils.

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