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A R Manukian

Publications and source records attributed to A R Manukian.

4 recordsLinked to original sources
PubMedDate not supplied

[Capsule formation in saprophytic yeasts].

Among ten carbon sources and five nitrogen sources tested, D-mannose (3%) and peptone (0.2%) were found to be the best ones for stimulating capsule formation by the yeast Cryptococcus magnus. Addition of yeast extract (0.1%) to the medium favoured formation of larger capsules. Elevated concentrations of mannose and peptone inhibited capsule formation. Comparison of the results obtained with the data about the effect of cultivation conditions on capsule formation by the pathogenic yeast revealed no considerable differences between the latter and the saprophytic yeast.

Carbohydrate Metabolism↗
PubMedDate not supplied

[Cytology of the dynamics of capsule formation in yeasts].

Changes in the dimensions and structure of capsules were examined using optical and electron microscopy in the yeast Cryptococcus magnus producing extracellular polysaccharides in the course of its batch cultivation. The mean thickness of capsules was minimal in the period of active budding, but is rapidly increased later on. The dimensions of capsules, as well as the distribution density of capsule fibrils, were maximal at the beginning of the stationary growth phase. The results indicate that the intensive process of capsule formation occurs in formed buds, young separated cells. They contain the greatest number of vesicles with fibrillar material moving from the centre of the cell toward its periphery. The vesicles are absent in the stationary growth phase when the capsules thicken on more. In the phase of dying off, the capsule size and the density of capsule fibres decrease because the capsule material dissolves in the medium. These findings are discussed in relation to capsule biosynthesis and production of extracellular polysaccharides by yeasts.

Cryptococcus↗
PubMedDate not supplied

[Yeast capsule ultrastructure].

The ultrastructure of capsules was studied in 12 yeast species producing extracellular polysaccharides and belonging to ascomycetous, basidiomycetous and asporogenous organisms using the method of ultrathin sections. On the whole, the structure of capsules was similar in these organisms: the capsules are formed by fibrils radially coming out of the outer surface of the cell wall. Unlike those of basidiomycetous yeasts, the capsules of ascomycetous organisms are characterized by a more ordered orientation of fibrils which run strictly parallel to one another. In the capsules of basidiomycetous organisms, fibrils usually interweave, often producing a fibrillar network; in certain species, fibrils stick together forming thick threads on the periphery of the capsule. Moreover, as a rule, these yeasts possess a distinct bright zone (halo) above the outer surface of the cell wall. These results as well as data available about the chemical composition and functions of the capsule indicate that there are radical differences the latter and the cell wall which make it possible to regard the capsule as an individual organelle of the yeast cell rather than as part of the cell wall.

Basidiomycota↗