A novel thermophilic, aerobic, endospore-forming bacterium, designated strain PizzoT, was isolated from geothermal volcanic environment. Samples were collected from the Pizzo sopra la Fossa site at Stromboli Island (Eolian Islands, south of Italy) at the high altitude of 918 m. Cells of strain PizzoT were rod-shaped and stained Gram-positive. Growth was observed between 50 and 75 degrees C (optimum 70 degrees C) and at pH 5.0-8.0 (optimum pH 7.0). NaCl (0.4%, w/v) supported growth and among the hydrocarbons tested none induced growth. The G+C content of the DNA was 54.1 mol% and the sequence analysis of the 16S rRNA gene showed that the new isolate was phylogenetically closely related to the members of the Bacillus rRNA Group 5. DNA-DNA hybridization studies revealed a borderline similarity between the new isolate and Geobacillus thermoleovorans DSM 5366T (69.8%) and Geobacillus kaustophilus DSM 7263T (63.4%). On the basis of phylogenetic analysis and physiological traits of the isolate, it should be described as a new member of the Geobacillus thermoleovorans species and it is proposed that strain PizzoT can be classified as Geobacillus thermoleovorans subsp. stromboliensis, subsp. nov. (ATCC BAA-979T; DSM 15393T).