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-
A SIMPLE TECHNIQUE FOR OBTAINING MATING TYPES IN HETEROTHALLIC DIPLOID YEASTS, WITH SPECIAL REFERENCE TO THEIR USES IN THE GENUS HANSENULA
A procedure has been devised by which large numbers of ascospore isolates may be obtained from yeasts without the use of a micromanipulator and auxiliary costly laboratory equipment or a need for the exacting skills which such tools require. The procedure is being continually applied in this laboratory to the genus Hansenula. Some of the species of this genus produce many ascospores, but so few are viable that isolation of mating types by micromanipulator is often impractical. Hence for genetical studies different experimental procedures are required. In this genus the ascus ruptures when it is mature and the liberated ascospores often agglutinate in large masses. This habit of early escapement from the asci also tends to thwart the usual tetrad analysis that starts with isolation of the four ascospores by micromanipulation. It is intended that the new procedure for isolating mating types and simple ancillary techniques for genetical analyses will be modified to whatever extent is necessary so that they may be applied to a genus like Saccharomyces where viability of ascospores is usually high and the ascus usually remains intact until the ascospores germinate. Various uses of the new procedure will be presented with examples taken from results obtained for the most part with diploid species of Hansenula. The principal procedure for the isolation of cultures derived from single ascospores is based on the fact that ascospores can withstand slightly more heat than vegetative cells. For most species of Hansenula, 57 or 58 C is employed.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.