ELECTRON MICROSCOPY OF ULTRATHIN SECTIONS OF SCHIZOSACCHAROMYCES OCTOSPORUS I

Abstract

Detailed studies of the process of cell division in yeast, particularly of the genus Schizosaccharomyces, have been few (Guilliermond, 1920; Knaysi, 1941), and little is known of the details of this process. Duraiswami (1953) points out that "It would be interesting to study the relationship between karyokinesis and cytokinesis in those yeasts where cell division is effected not by budding but by the formation of a septum in the middle-as for instance in the Schizosaccharomycetes. It is very likely that a close correlation between these two processes exists in these yeasts." Since the Schizosaccharomycetes appear to divide in a manner which is analogous to that described for bacterial cells, a study by electronl microscopy of cytological changes occurring in Schizosaccharomyces octosporus during cytokinesis and karyokinesis was carried out not only to elucidate details of the process of cell division, but also to compare and relate these to the, process of cell division described for bacterial cells. MATERIALS AND METHODS The culture used in these studies was S. octosporus strain NRRL Y-854, obtained from Dr. L. J. Wickerham. Cells were routinely grown in a glucose-yeast extract medium (glucose, 1.0 per cent; yeast extract, 2.0 per cent; peptonie, 0.5 per cent; KH2P04, 0.1 per cent; and MgSO4, 0.05 per cent). The pH of the medium was adjusted to 7.0 prior to sterilization. When a solid medium was required, 1.5 per cent agar was

STUDIES ON THE FINE STRUCTURE OF CANDIDA ALBICANS, WITH SPECIAL REFERENCE TO INTRACYTOPLASMIC MEMBRANE SYSTEM

“…It is a generally accepted view that the vacuole is not an integral part of the nuclear apparatus of yeasts as had been proposed by Lindegren et al (1956). Previous studies by Hashimoto et al (1958 and, Conti and Naylor (1959, 1960a, and 1960b), Vitols et al (1961), and Thyagarajan et al (1962) have led to a similar conclusion. The present study in C. albicans provides evidences that the vacuole is not a permanent cell inclusion, as the vacuoles are generally absent in vegetative cells, although they are visible in yeast-like cells grown on media for chlamydospore production which are a kind of starvation media.…”

“…In C. albicans, as described above, a distinct double nuclear membrane with pores is observable, and it is believed to be a unit membrane. During nuclear division the nuclear membrane is found to persist and the nucleus appears to divide by a simple process of elongation and constriction similar to that observed in several yeasts (Thyagarajan et al ., 1962;Hashimoto et al, 1959;Conti and Naylor, 1959).…”

Pneumocystis carinii Delanoë, its Ultrastructure and Ultrastructural Affinities*

“…However, Pneumocystis seems not to be identical with such common yeasts as Saccharomyces, Schizosaccharomyces, Rhodotoruh or Candida as was proposed earlier. Altho its cyst (presumably an ascus) contains 8 intracystic bodies (presumably ascospores) , it cannot be compared with S. octosporus as proposed by Giese (34) because the fine structure of the latter species is not the same (20). Pneumocystis is not a yeast infected by a virus as was suggested earlier (81).…”

“…In further development, the membrane of the ascospore grows thicker, and a thick, electron-transparent layer is deposited between the inner and outer membranes to form the ascospore cell wall (4, 20, 37, 64). Upon germination, the ascospores increase in volume by swelling, shed the cell wall and leave the ascus in a form similar to the vegetative organism (20,38). The similarity of this process to the mechanism of intracystic body formation in Pneumocystis is as follows: 1 ) the formation of the membrane of each intracystic body within the cytoplasm is in agreement with the ascospore delineation mechanism in fungi.…”

DIVISION OF MICROBIOLOGY: PROBLEMS OF FIXATION AND STAINING IN MICROBIAL CYTOLOGY*

“…An additional undesirable feature to be considered in interpreting microbial structure with the electron microscope is the extractive influence of fixing solutions, particularly potassium permanganate, described by Bradbury and Meek (1960). T h i s effect is illustrated in yeast where the cytoplasm and nuclei p o s s e s s characteristics of granulation and texture so remarkably identical that only the retention of nuclear membranes indic a t e s t h e occurence of sectioned nuclei in the specimens (Conti and Naylor, 1959;Vitols et al, 1961).…”