A strain of an achlorophyllic alga, named PR24T, was isolated from cow milk samples from the state of Minas Gerais, Brazil. Based on 18S rDNA, 28S rRNA, D1/D2 region of the LSU rDNA and SSU rRNA gene sequence similarities, this strain was found to be a member of the genus Prototheca and closely related to Protothecablaschkeae SAG2064T. However, the novel strain could easily be distinguished from recognized Prototheca species by internal transcribed spacer, species-specific PCR, single-strand conformation polymorphism-PCR analysis and phenotypic characteristics. The inability to grow in Sabouraud broth at pH 4.0 and the different cellular fatty acid composition clearly distinguished PR24T from the reference strain of P. blaschkeae. The combination of genotypic and phenotypic data indicates that strain PR24T represents a subspecies of P. blaschkeae, for which the name Prototheca blaschkeae subsp. brasiliensis subsp. nov. is proposed. The respective type strain is PR24T (=DSM 103592T=IHEM 26958T).
Keywords: Prototheca blaschkeae subsp. brasiliensis; cow milk; protothecal bovine mastitis.