Species of the genus Prototheca are achlorophyllous algae and ubiquitous in nature, and so far, six species have been listed in this genus: Prototheca wickerhamii, Prototheca zopfii, Prototheca blaschkeae, Prototheca cutis, Prototheca stagnora and Prototheca ulmea. A strain of the genus Prototheca, IFM 53848 T , was isolated in Japan from a patient with systemic protothecosis and had been designated P. wickerhamii. Our previous study, by using PCR analysis, revealed that its SSU rRNA gene

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... was distinctively larger than that of P. wickerhamii and other species of the genus Prototheca. In this study, molecular analysis showed that the exceptionally large SSU rDNA of IFM 53848 T contains four group I introns. The morphology of IFM 53848 T was indistinguishable from those of P. wickerhamii or P. cutis, and phylogenetic analyses, based on the sequences of the SSU rDNA exons and the D1/D2 region of the large subunit rDNA, indicated that IFM 53848 T was closely related to P. cutis. On the other hand, unlike P. cutis, IFM 53848 T failed to assimilate fructose or lysine and grew well at higher temperatures of up to 42 8C. In addition, the nucleotide sequence of the ribosomal internal transcribed spacer and the matrix assisted laser desorption ionization time-of-flight mass spectrometry profile of IFM 53848 T were clearly distinct from those of P. cutis. The results strongly suggest that IFM 53848 T represents a novel species, and so the seventh member of the genus Prototheca, which we have named Prototheca miyajii sp. nov. The unique characteristics of the strain may provide useful insights into the systematic taxonomy of the genus Prototheca. Abbreviations: ITS, internal transcribed spacer; MALDI-TOF, matrix assisted laser desorption ionization time-of-flight mass spectrometry. The GenBank/EMBL/DDBJ accession numbers for nucleotide sequences of the SSU rDNA, ITS and D1/D2 region of the LSU rDNA of strain IFM 53848 T are KP898383, KP898384 and KP898385, respectively. The accession numbers for the sequences of the corresponding regions of strain IFM 54820 are KP898386, KP898387 and KP898388, respectively. The accession number for the ITS sequence of P. cutis JCM 15793 T is KP898389. Prototheca miyajii sp. nov. P. wickerhamii genotype 2 (FL11-0001) P. wickerhamii genotype 1 (IFM-56379 T ) P. wickerhamii genotype 1 (IFM 56379 T ) P. cutis (IFM 54820) P. miyajii (IFM 53848 T ) P. miyajii (IFM 53848 T ) P. zopfii genotype 1 (SAG 2063 T ) P. zopfii genotype 2 (SAG 2021 T ) P. zopfii genotype 1 (SAG 2063 T ) P. zopfii genotype 2 (SAG 2021 T ) P. zopfii genotype 2 (SAG 263-4 T ) P. blaschkeae (SAG 2064 T ) P. stagnora (JCM 9641 T ) P. ulmea (ATCC 50112 T ) P. cutis (JCM 15793 T ) P. cutis (JCM 15793 T ) C. vulgaris (SAG 211-11b T ) A. protothecoides (SAG 211-7a T ) P. ulmea (ATCC 50112 T ) P. stagnora (JCM 9641 T ) P. blaschkeae (SAG 2064 T ) P. cutis (IFM 54820)