Dipodascus tetrasporeus sp nov., an ascosporogenous yeast isolated from deep-sea sediments in the Japan Trench

Dipodascus tetrasporeus sp. nov. is described as a novel yeast species in the family Dipodascaceae to accommodate an isolate recovered from sediments collected on the deep-sea floor in the north-western Pacific Ocean. In the clade comprising the genera Dipodascus, Galactomyces and Geotrichum, this is the only species that forms asci that bear four ascospores. The ascospore is surrounded by an irregular exosporium wall, similar to what is observed in the genus Galactomyces, but they are released by rupture, which is characteristic of Dipodascus and not Galactomyces. D. tetrasporeus is remarkably divergent (> 10% difference) in its D1/D2 26S rDNA sequence from any other known species. Although maximum-likelihood analysis of combined 18S rDNA and D1/D2 26S rDNA sequences cannot elucidate a reliable position for this species, it was placed among Geotrichum carabidarum, Geotrichum cucujoidarum, Geotrichum fermentans and Geotrichum, histeridarum, which also have morphological and physiological affinity with the species. The species is homothallic. The type strain of Dipodascus tetrasporeus sp. nov. is strain SY-277(T) (=NBRC 103136(T) =CBS 10071(T)).