Kluyveromyces osmophilus, a new yeast species
In 1962 Dr. R. ANTOINE of Mauritius sent a number of yeast strains isolated from sugar for identification to the Yeast Division of the Centraalbureau voor Schimmelcultures at Delft. One of these strains is considered to belong to a new species for which the name Kluyverornyces osmophilus is proposed. It will be described in the following part. This yeast strain was conspicuous by forming oval to reniform spores which were easily liberated from the ascus. When first studied, sporulation was abundant. The picture of the spores in this paper. (fig 2) is an electron micrograph of ultra-thin sections of a preparation fixed at that time with osmic acid and uranyl acetate according to RYTER et al. (1958). Unfortunately, the sporulating ability has been lost after maintaining the yeast for two years on malt agar. The yeast, grown on malt agar, was investigated according to the methods of WICKERHAM (1951) and of LODDER & KREGERVAN RIJ (1952). As regards the fermentation and assimilation reactions some remarks can be made. Fermentation of a 2% (w/v) glucose solution in a Durham tube was rather slow, i.e. the insert tube was filled up with gas after 10--14 days' incubation at 25 ° C. A 10% glucose solution gave the same result after 5--7 days, while a 30% glucose solution had a gas-filled insert tube after 5 days. Apparently, in solutions with a higher sugar concentration the fermentation rate was high at an earlier period. The assimilation test with the auxanographic method gave positive results for glucose and galactose only. The assimilation test in a synthetic liquid medium with glucose as the sole source of carbon in a concentration of 0 .50, read after one week at 25 ° C, show-
Kluyveromyces osmophilus is not a synonym of Zygosaccharomyces mellis; reinstatement as Zygosaccharomyces osmophilus comb. nov.
Kluyveromyces osmophilus, a single-strain species isolated from Mozambique sugar, has been treated a synonym of Zygosaccharomyces mellis. Analyses of D1/D2 LSU rRNA gene sequences confirmed that the species belongs to the genus Zygosaccharomyces but showed it to be distinct from strains of Z. mellis. During studies of yeasts associated with stingless bees in Brazil, nine additional isolates of the species were obtained from unripe and ripe honey and pollen of Scaptotrigona cfr. bipunctata, as well as ripe honey of Tetragonisca angustula. The D1/D2 sequences of the Brazilian isolates were identical to those of the type strain of K. osmophilus CBS 5499 (=ATCC 22027), indicating that they represent the same species. Phylogenomic analyses using 4038 orthologous genes support the reinstatement of K. osmophilus as a member of the genus Zygosaccharomyces. We, therefore, propose the name Zygosaccharomyces osmophilus comb. nov. (lectotype ATCC 22027; MycoBank no. MB 833739).
Ascospores of Endomycopsis selenospora (Nadson et Krassilnikov) Dekker
IN 1928 Nadson and. Krassilnikov1 described a yeast isolated from the exudate of oaks in Kalouga, U.S.S.R. According to the original description, the yeast formed true mycelium as well as budding cells. Its asci contained four falcate spores. Nadson and Krassilnikov further stated that the ascospores appeared to have a double membrane, the latter being visible as two colourless appendages at the extremities of the spores (Fig. 1). On account of the characteristic ascospore shape the authors erected a new genus for this yeast and named it Guillier-mondella selenospora.