Random sequence analysis of genomic DNA of an anaerobic, thermophilic, halophilic bacterium, Halothermothrix orenii

A pBluescriptSK+ vector library consisting of 3.360 clones with an average insert size of 3.5 kb was constructed from the genome of Halothermothrix orenii, a halophilic and thermoanaerobic member of the family Haloanaerobiaceae. From both ends, 77 clones were sequenced using T3 and T7 vector primers generating 154 sequence tags, representing approximately 85 kb of the genome. Comparison of sequence tags against the Gen-Bank database using BLASTX identified 66 known proteins and 15 conserved hypothetical proteins. The putative proteins included a V-ATPase, hydrogenases, and enzymes with potential for industrial applications. The overall G + C% of the codons used was 42.9% with a third-position G + C content of 38.6%. High levels of excess acidic amino acids were not detected in the putative proteins of H. orenii as compared to the mesophilic haloanaerobes. This lack may be the result of reduced activity of acidic, halophilic enzymes at high temperatures and intermediate salt concentrations.