Distribution of 16S rRNA introns among the family Thermoproteaceae and their evolutionary implications.

Novel 16S rRNA introns were detected in four new strains within the family Thermoproteaceae. Pyrobaculum oguniense TE7(T) and Thermoproteus sp. IC-062 housed introns of 32 and 665-668 bp after positions 1205 and 1213 ( Escherichia coli numbering system), respectively. Caldivirga maquilingensis IC-167(T) had two introns of 37 and 140 bp after positions 901 and 908, respectively. Vulcanisaeta distributa IC-065 had a 691-bp intron after position 1391. All the introns larger than 650 bp encoded the LAGLI-DADG type proteins. The intron-encoded proteins of P. oguniense TE7(T) and Thermoproteus sp. IC-062 are cognate with the proteins encoded by introns inserted at the same position in other Pyrobaculum/ Thermoproteus strains and phylotypes. The intron-encoded protein of V. distributa IC-065 is partially related to that of a Pyrobaculum phylotype. A large-scale deletion in the second intron of Caldivirga maquilingensis IC-167(T) is suspected. Based on these newly found introns and hitherto known 16S rRNA introns, the evolutionary movements of the 16S rRNA introns and the encoded LAGLI-DADG type proteins are discussed.