Very similar strains of Halococcus salifodinae are found in geographically separated Permo-Triassic salt deposits

Institute of Genetics and General Biology, Hellbrunnerstr. 34, A- 5020 Salzburg, Austria 1 Dept of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK 2 Institute of Microbiology and Genetics, University of Vienna, Dr Bohrgasse 9,A-1030 Vienna, Austria 3 Department of Microbiology, University of Regensburg, Universit ätsstraße 31, D-93053 Regensburg , Germany 4 Botanical Institute of the University of Munich, Menzinger Str. 67, D-80638 Munich, Germany 5 Author for correspondence: Helga Stan-Lotter. Tel: +43 662 8044 5756. Fax: +43 662 8044 144. e-mail: helga.stan-lotter{at}sbg.ac.at The authors have previously isolated a novel extremely halophilic archaeon, Halococcus salifodinae BIp, from Austrian rock salt deposited about 250 million years ago. In this study they compared strain BIp with two other halococci isolated independently from geographically distant salt deposits of similar age, and with two recent isolates (N1 and H2) from the same site as strain Blp. Strain BG2/2 was from a salt mine in Germany and strain Br3 from a halite deposit in England; both resembled Hc. salifodinae BIp in cellular and colonial morphology. Strains BIp, BG2/2 and Br3 had identical 16S rRNA sequences, very similar whole-cell protein patterns, which were different from those of other halococci, similar G+C contents and identical sequences in a 108-base insertion in their 5S rRNA gene. Other similarities included composition and relative abundances of polar lipids, antibiotic susceptibility, enzymic activities and Fourier-transform infrared spectra. Strains N1 and H2 showed similar morphology, whole-cell protein patterns and biochemical characteristics as strains BIp, Br3 and BG2/2. Their partial 16S rRNA sequences (682 and 641 bases, respectively) were indistinguishable from those of strains BIp, Br3 and BG2/2. Therefore strains N1 and H2 can be considered as reisolates of Hc. salifodinae which were obtained 8 years after the first samples were taken from that mine. The results presented suggest that viable halophilic archaea, which belong to the same species, occur in widely separated evaporite locations of similar geological age, and support the notion that these halophilic isolates from subterranean salt deposits may be the remnants of populations which inhabited ancient hypersaline seas. Keywords: archaea, Halococcus , subterranean microbiology, salt deposits, prokaryotic longevity Abbreviations: FT-IR, Fourier-transform infrared; PG, glycero