Three strains (N002, N069 and PT31T
) of a novel thermotolerant methylotrophic yeast species
belonging to the genus Pichia were isolated from soil collected in Thailand by three consecutive
enrichments in methanol broth at room temperature. They were categorized as thermotolerant
strains on the basis of their good growth below 206C and up to a high temperature (376C).
The major characteristics of the three strains included the following and placed them in the
genus Pichia: the formation of four helmet-/hat-shaped ascospores in a deliquescent ascus
that might be unconjugated or produced by conjugation between a cell and its bud or between
independent cells; multilateral budding; the presence of ubiquinone Q-7; negative for Diazonium
blue B colour and urease reactions; and the absence of arthrospores and ballistospores. The
three strains differed by one to three nucleotide substitutions in the sequences of the D1/D2
domain of the large-subunit rDNA sequence. Phylogenetic analysis revealed that their closest
species was Pichia dorogensis, but with 11–13 nucleotide substitutions in 554 nt. The
phenotypic characteristics of the three strains were the same. The strains could be
distinguished from P. dorogensis by a number of phenotypic characteristics. On the basis of
the above findings, these three strains were assigned to a single novel species of Pichia, for
which the name Pichia thermomethanolica sp. nov. is proposed. The type strain is PT31T
(=BCC 16875T
=JCM 12984T
=CBS 10098T
).