Evidence of recent lateral gene transfer among hyperthermophilic Archaea

Abstract

A total of 153 nucleotide differences were found over a contiguous 16 kb region between two hyperthermophilic Archaea, Pyrococcus furiosus and Thermococcus litoralis . The 16 kb region in P. furiosus is flanked by insertion sequence (IS) elements with inverted and direct repeats. Both IS elements contain a single open reading frame (ORF) encoding a putative protein of 233 amino acids identified as a transposase. This 16 kb region has the features of a typical bacterial composite transposon and represents a possible mechanism for lateral gene transfer between Archaea or possibly between Archaea and Bacteria. A total of 23 homologous IS elements was found in the genome sequence of P. furiosus , whereas no full‐length IS elements were identified in the genomes of Pyrococcus abyssi and Pyrococcus horikoshii . Only one IS element was found in T. litoralis. In P. furiosus and T. litoralis , the 16 kb region contains an ABC transport system for maltose and trehalose that was characterized biochemically for T. litoralis . Regulation of expression studies showed that the malE gene, located on the transposon, and the encoded trehalose/maltose‐binding protein (TMBP) are induced in the presence of maltose and trehalose in both P. furiosus and T. litoralis . The implications of transposition as a mechanism for lateral gene transfer among Archaea are discussed.