Internal transcribed spacer regions of rRNA genes of Pneumocystis carinii from monkeys

Analysis of sequence variations among isolates of Pneumocystis carinii f. s p, macacae from 14 Indian rhesus monkeys (Macaca mulatta) at the internal t ranscribed spacer (ITS) regions of the nuclear rRNA gene was undertaken. Li ke those from P, carinii I, sp, hominis, the ITS sequences from various P. carinii I, sp, macacae isolates were not identical, Two major types of sequ ences were found, One type of sequence was shared by 13 isolates. These 13 sequences were homologous but not identical. Variations were found at 13 of the 180 positions in the ITS1 region and 28 of the 221 positions in the IT S2 region. These sequence variations were not random but exhibited definite patterns when the sequences were aligned. According to this sequence varia tion, ITS1 sequences were classified into three types and ITS2 sequences we re classified into five types. The remaining specimen had ITS1 and ITS2 seq uences substantially different from the others. Although some specimens had the same ITS1 or ITS2 sequence, all 14 samples exhibited a unique whole IT S sequence (ITS1 plus ITS2), The 5.8S rRNA gene sequences were also analyze d, and only two types of sequences that differ by only one base were found. Unlike P. carinii f, sp, hominis infections in humans, none of the monkey lung specimens examined in this study were found to be infected by more tha n one type of P, carinii I. sp, macacae. These results offer insights into the genetic differences between P. carinii organisms which infect distinct species.