A thermophilic, spore-forming bacterial strain L1
T was isolated from hot compost “Pomigliano Environment” s.p.a., Pomigliano, Naples, Italy. The strain was identified by using a polyphasic taxonomic approach. L1
T resulted in an aerobic, gram-positive, rod-shaped, thermophilic with an optimum growth temperature of 68°C chemorganotrophic bacterium which grew on hydrocarbons as unique carbon and energy sources and was resistant to heavy metals. The G+C DNA content was 43.5 mol%. Phylogenetic analysis of 16S rRNA gene sequence and Random Amplified Polymorphic DNA-PCR (RAPD-PCR) analysis of L1
T and related strains showed that it forms within
Geobacillus toebii, a separate cluster in the
Geobacillus genus. The composition of cellular fatty acids analyses by Gas-Mass Spectroscopy differed from that typical for the genus
Geobacillus in that it is lacking in
iso-C15 fatty acid, while
iso-C16 and
iso-C17 were predominant. Isolates grew on a rich complex medium at temperatures between 55–75°C and presented a doubling time (
td) of 2 h and 6 h using complex media and hydrocarbon media, respectively. Among hydrocarbons tested,
n-decane (2%) was the more effective to support the growth (1 g/L of wet cells). The microorganism showed resistance to heavy metal tested during the growth. Furthermore, intracellular α-galactosidase and α-glucosidase enzymatic activities were detectable in the L1
T strain. Based on phenotypic, phylogenetic, fatty acid analysis and results from DNA-DNA hybridization, we propose assigning a novel subspecies of
Geobacillus toebii, to be named
Geobacillus toebii subsp.
decanicus subsp. nov., with the type strain L1
T (=DSM 17041=ATCC BAA 1004).
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