Modifications of the cell wall of yeasts grown on hexadecane and under starvation conditions

Abstract

Electron-microscopic examinations have demonstrated local modifications in the cell wall of the yeast Candida maltosa grown on hexadecane. In our earlier studies, these modified sites, observed in other yeasts grown on oil hydrocarbons, were conventionally called 'canals'. The biochemical and cytochemical studies of C. maltosa have revealed a correlation between the formation of 'canals' and decrease in the amount of cell wall polysaccharides, glucan and mannan. The ultrathin sections and surface replicas have shown that the 'canals' are destroyed by pronase, thus indicating that a significant proportion of their content is represented by proteins. This finding was compatible with our earlier data on the localization of oxidative enzymes in 'canals' and possible participation of the 'canals' in the primary oxidation of hydrocarbons. A completely unexpected and intriguing phenomenon has been the appearance of 'canals' in the yeast C. maltosa under starvation conditions. Unlike the yeasts grown on hexadecane, mannan almost disappears in starving cells, while the quantity of glucan first decreases and then is restored to its initial level. The role of 'canals' in starving cells is as yet unclear; it is assumed that they acquire exoenzymes involved in the utilization of products of cell lysis in the starving population. In the future, 'canals' of starving cells will be studied in connection with their possible participation in apoptosis.

The Extracellular Vesicles Containing Inorganic Polyphosphate of Candida Yeast upon Growth on Hexadecane

“…Electron microscopic analysis of the cell surface and their environment during growth on glucose revealed as expected nothing unusual (Figure 2a-c). The cells utilizing hexadecane had modified cell wall zones on the surface (canals) similar to observed earlier in hexadecane-grown C. maltosa [20][21][22][23]. The presence of extracellular vesicles was also confirmed, as well as with fluorescence microscopy.…”

“…In addition, it has been found that similar structures are also formed in the yeast cell wall during carbon starvation. Electron microscopic and biochemical studies revealed for the first time the formation of canals in the cell wall during the growth on hydrocarbons [ 20 , 21 , 22 , 23 ]. The unique properties of canals—substrate dependence, hydrophobicity, high concentration of oxidizing enzymes and strong chemical and mechanical connection with other components of the cell wall—indicate that these structures are the key components of metabolic interaction with the environment.…”

“…Summing up, we assume that the yeast growth on alkanes is accompanied by significant changes in the protein and carbohydrate profile of the cell wall, and the primary oxidation and further transporting of oxidized derivatives into the cell are concentrated in specific molecular machines of the cell wall, called canals. We have obtained a number of cytochemical and microscopic evidence that these structures of C. maltosa contain oxidative enzymes related to cytochromes, as well as specific structural polysaccharides and inorganic polyphosphates, which apparently play the role of structural organization and regulation of activity for cytochromes [ 20 , 21 , 22 , 23 ]. This concept does not contradict the idea of the important role of endoplasmic reticulum and peroxisomes in the metabolism of alkanes.…”

Structural changes in the cell envelope of Yarrowia lipolytica yeast under stress conditions

“…Earlier, there has been nothing known in the literature about the existence of such structures as pore channels in the yeasts Y. lipolytica. Formation of similar (but larger and D r a f t structurally slightly different) 'canals' has been shown for some yeasts grown on oil hydrocarbons, namely, Schwanniomyces occidentalis, Candidat ropicalis and C. maltose (Dmitriev et al 2016). The role of these 'canals' was assumed in connection with their possible participation in apoptosis.…”