Substructural studies on sporulation of Saccharomycopsis lipolytica

Abstract

During sporulation of diploids from crosses between different strains of the yeast Saccharomycopsis (Candida) lipolytica irregular numbers of ascospores per asciis have been observed. Using the serial section method it could be shown now by means of electron microscopy that in one-, two-, and three-spored asci unenclosed "naked" nuclei occur additionally to nuclei incorporated in mature spores. It was demonstrated that the production of less than four spores per ascus in this yeast is not the result of a lack of meiotic products but of the nonutilization of nuclei from meiosis. I n 2-4 spored asci usually four products of meiosis in form of enclosed and free nuclei could be demonstrated which indicate a normal meiotic division. All ascospores derived from asci with different spore numbers are uninuclear. It is assumed that a defect in spore formation caused by structural changes of chromosomes or aneuploidy should give rise to the occurrence of non incorporated nuclei and spore irregularity. It was concluded that meiosis and spore formation in Further works dealing with complementation, genetic recombination, conjugation, and sporulation opened the way to extensive and fundamental genetic studies of this yeast which is of special interest because of its ability to metabolize hydrocarbons and to convert this ubiquous material into single cell protein and other products Strains of Srn. Zipolytica isolated froin natural sources or strains from culture collections which recently have been shown t o possess a perfect state after crosses are known to form on sporulation niedium frequently asci with an irregular number of ascospores per ascus. The spores usually vary strongly in their shape and their fertility is very low, Genetic analysis and strain improvement is handicapped by these irregularities. Therefore, in certain laboratories attempts have been made to construct strains with whole tetrads and increased spore fertility for tetrad analysis. The background of spore irregularities in this yeast, however, remains open so far. The only explanation for abnormal spore forniation was given by ESSER and STAHL (1976) whch assumed on the base of light microscopic and genetical studies that the variability in the ascospore number is caused by the absence of a correlation between meiotic divisions and spore wall formation. This assumption differs strongly from the situation in Saccharomyces cerevisiae (BLACK and GORMAN 1971

Untersuchungen zur Regulation der Enzyme des Glyoxylatzyklus bei Saccharomycopsis lipolytica I. Einfluß der C‐Quelle auf die Aktivität von Isocitratlyase und Malatsynthase

“…Diesen Stamm erhielten wir unter der Bezeichnung Candida Zipolytica (2z 2b). Die Einordnung in die Gattung Saccharomycopsis erfolgte auf Grund seines Sexualverhaltens, wo dieser Stamm die Bezeichnung H 222 erhielt (WEBER 1979).…”

Improvement of sporulation in the yeastYarrowia lipolytica

“…Isolation of single ascospores from such strains by micromanipulation is possible but laborious and complicated because these spores are closely attached to each other (Ogrydziak et al, 1978(Ogrydziak et al, , 1982. In contrast to the situation in certain other yeasts used in genetic studies, sporulation in Y. lipolytica is known so far to occur only on complex sporulation media where asci are formed almost exclusively on hyphi (Ogrydziak et al, 1978;Weber, 1979). Hitherto conditions for optimal sporulation of this yeast were not intensively investigated.…”

“…ASM (acetate sporulation medium) contained 0.14~ sodium acetate and 0.04~o glucose. VSM (vegetable juice sporulation medium) was used as described by Weber (1979). For CSM (citrate sporulation medium), minimal medium according to Barth and Kfinkel (1979) was supplemented with 20 g. 1-1 sodium citrate.…”

“…For transmission and scanning electron microscopic studies samples of sporulating mycelial or yeast cells were prepared as described previously (Weber, 1979).…”

Development of breeding stocks of the yeast Saccharomycopsis lipolytica by methods of moderate inbreeding

“…Media: Complete medium (yeast extract-pepton-glucose) (YEPG) (SHERMAN et al 1974) ; minimal medium (MM) (MISHINA et al 1976, composition of trace elements as described by LINOENS and HELLMANN 1958); medium for mating (YM) (WICKERHAM 1951); sporulation medium (SpM) (WEBER 1979).…”