Alicyclobacilli from an unexplored geothermal soil in Antarctica: Mount Rittmann

Abstract

The isolation of three species from soil samples from an unexplored site in Antarctica, belonging to the Alicyclobacillus genus, is reported. The isolates, named MR1, MR2 and MR4, were from 30 samples of geothermal soil from Mount Rittmann. All the isolates had lipids based mainly on fatty acids possessing a terminal cyclohexane; hopanoid and quinones of MK-7 were also present. All isolates were characterized by phenotypic features and the isolate MR1 was subjected to genetic analyses. The isolates were thermoacidophilic, showing an optimum temperature of 63°C and an optimum pH of 3.5–4.0. They were able to grow in the temperature range 45–70°C. The percentage C+G of DNA of MR1 was 64.9% and showed a 16S rDNA similarity of 99.3% with Alicyclobacillus acidocaldarius ATCC 43034 and a DNA-DNA homology of 69.7% with A. acidocaldarius DSM 446. The strain MR1 is unable to produce amylolytic activity under different growth conditions. It is proposed to accommodate MR1 in the genus Alicyclobacillus as subspecies rittmannii of A. acidocaldarius.