http://dx.doi.org/10.4014/kjmb.1301.01004 Korean J. Microbiol. Biotechnol. (2013), 41(3), 278–283 http://dx.doi.org/10.4014/kjmb.1301.01004 pISSN 1598-642X eISSN 2234-7305 Korean Journal of Microbiology and Biotechnology Characterization of the Thermophilic Bacterium Geobacillus sp. Strain GWE1 Isolated from a Sterilization Oven Correa-Llantén, Daniela 1,2 *, Juanita Larraín-Linton 1 , Patricio A. Muñoz 1,2 , Miguel Castro 1 , Freddy Boehmwald 1 , and Jenny M. Blamey 1,2 * 1 Fundación Biociencia, Santiago, Chile 2 Doctorado en Biotecnología, Universidad de Santiago de Chile, Facultad de Química y Biología, Santiago, Chile Received : January 8, 2013 / Revised : May 8, 2013 / Accepted : July 12, 2013 Introduction The genus Geobacillus was introduced by Nazina et al. (2001) [19]. To date, 16 different species of this genus have been reported [4]. Although the searching of thermophiles has been usually performed in ‘hot’ environments, these thermophilic bacilli have been also found in cool soil environments [1, 15, 16]. In particular, members of genus Geobacillus are widely dis- tributed and not restricted to specialized nutritional environ- ments. Oxygen is usually the terminal electron acceptor for aerobic respiration in members of genus Geobacillus, how- ever, facultative anaerobes of this genus can replace oxy- gen by nitrate. They are Gram-positive, rod-shaped, motile cells, present in single or short chains and includes microorganisms with optimal growth temperature ranging between 37-75°C [19]. Geobacillus have been described as sources of interest- ing enzymes such as proteases [3], lyases [7], esterases [17], amylase and β-galactosidase and cellulolytic enzymes [24] among others. This report presents the isolation of Geobacillus wiegelii (GWE1), a microorganism isolated from a sterilization oven, an environment where temperature can easily sur- pass 150ºC. Drastic changes in humidity and periodic cleaning desiccation cycles of the equipment with oxidizing solutions, organic solvents, among others, make this an extremely hostile environment previously thought to be unable to sustain life. Here we described the isolation and characterization of a a new microorganism Geobacillus wiegelii belonging to genus Geobacillus. A gram-positive, rod-shaped, spore-forming, motile thermophilic bacterium was isolated from a sterilization oven. The microor- ganism GWE1, formally named Geobacillus wiegelii identified as a member of the genus Geobacillus. GWE1 grew under aerobic conditions of between 60-80ºC (optimum 70ºC), in a pH range of 3.0-8.0 (optimum pH 70ºC 5.8), and between 0 and 2 M NaCl (optimum 0.3 M). The membrane polar lipids were dominated by branched saturated fatty acids, which included as the major constituents; iso-15:0 (13.3%), 16:1(ω7) (12.8%), 16:0 (28.5%), iso-17:0 (13.5%) and anteiso-17:0 (12.3%). The DNA G+C content was 47.2 mol% (determined by HPLC). The 16S rRNA gene sequence of GWE1 showed a high similarity with Geoba- cillus caldoxylosilyticus (97%). However, the level of DNA–DNA relatedness was only 58%. These data suggest that GWE1 is probably a novel specie of the genus Geobacillus. Keywords: Thermophilic bacterium, Geobacillus, sterilization oven *Corresponding authors C.-L. D. Tel: +56-2-343-25-78 E-mail: dcorrea@bioscience.cl J. M. B. Tel: +56-2-343-25-78 E-mail: jblamey@bioscience.cl © 2013, The Korean Society for Microbiology and Biotechnology