Diversity within the current algal species Prototheca zopfii: a proposal for two Prototheca zopfii genotypes and description of a novel species, Prototheca blaschkeae sp. nov.

In order to clarify the intraspecies taxonomic position of the non-photosynthetic algal species Prototheca zopfii, as well as the aetiology of bovine mammary protothecosis, a selection of P. zopfii strains isolated from clinical cases of protothecal mastitis and from various environmental habitats was characterized using a polyphasic molecular approach. Based on sequence analysis of the 18S rRNA gene, which showed distinct differences between the three currently known biotypes or 'variants', specific oligonucleotides were designed and used in biotype-specific PCRs. Furthermore, the pattern of cellular fatty acids was evaluated. Typing by means of these techniques revealed that the previously defined biotypes of P. zopfii were clearly different. Based on sequence analysis, the pattern of fatty acids and physiological characteristics, it is proposed that biotype 3 should be reclassified as representing a novel species, Prototheca blaschkeae sp. nov. (type strain, RZIII-3(T) = SAG 2064(T)). Furthermore, it is proposed that P. zopfii merits reclassification as a species comprising at least two genotypes that in future could probably be considered to represent two subspecies.