Abstract
Nucleotide sequences of small subunit ribosomal RNA (SSUrRNA) of five microsporidia infectious to the silkworm, Bombyx mori, are described. Of microsporidia examined, the sequence of SSUrRNA of Nosema bombycis SES-NU was very similar to that of N. bombycis Sd-NU-IW8401, both having lengths of 1, 232, while those of Nosema sp. NIS-M11 and Vairimorpha sp. NIS-M12 were 1, 247 nucleotides in length, and that of Pleistophora sp. Sd-NU-IW8201 was 1, 248. Similarity of SSUrRNA sequences between N. bombycis SES-NU and N. bombycis Sd-NU-IW8401 was 99.2%, between NIS-M11 and NIS-M12 96.7%, and between N. bombycis SES-NU and NIS-M11 85.1%. Pleistophora sp. Sd-NU-IW8201 had the least similarity to the other microsporidia examined. SSUrRNA secondary structure models showed that Nosema sp. NIS-M11 had the same helices as Vairimorpha sp. N15-M12; however, NIS-M11 was different from N. bombycis SES-NU in that it had another helix, suggesting that NIS-M11 was more likely to be a microsporidium of genus Vairimorpha than Nosema. The secondary structure of SSUrRNA of Pleistophora sp. Sd-NU-1W8201 was far different from any other microsporidia examined.
