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

Abstract

Ultrastructural changes in the cell envelope of the yeast Yarrowia lipolytica as a stress response were examined using electron microscopy. The formation of new cellular surface structures, including membrane vesicles, pore channels, and wall surface globules, were shown for the first time under conditions of oxidative (endogenous and exogenous) or thermal stress. This demonstrates once again that under stress conditions the microorganisms reveal properties previously unknown for them. Particularly noteworthy is the accumulation of silicon in the surface globules, which was revealed by X-ray microanalysis of the elemental composition of thin sections of cells. A multilayered plasmalemma instead of a 3-layered one is also characteristic for stressed cells. The envelope modifications above were observed only as a stress response and were not detected in stationary-growth-phase yeast cells that assume different physiological states. A decrease in the intracellular level of cAMP allows us to assume that a common factor activates defensive mechanisms thus explaining the similarity of the response under different stress conditions. The data presented not only enable visualization of the yeast stress response and add to our awareness of the diversity of adaptive reactions, but they also raise questions about the interrelations of the stress phenomena and their functional necessity in the cell.

“Fight-flight-or-freeze” – how Yarrowia lipolytica responds to stress at molecular level?

“…Based on a comparison with the control conditions, exposure to 0.5 mM Pb (II), 0.5 mM Zn (II), 0.5 mM Cr (III), and 0.1 mM Cr (VI) contributed to the highest filamentation degree and formation of nanostructures on the yeast cell surfaces. Those observations were consistent with what was observed by Biryukova et al ( 2011 ) and Arinbasarova et al ( 2018 ) under simulated oxidative stress. Specifically, yeast-to-mycelium transition was observed in the presence of Cr (VI) and Pb (II), significant elongation of the cells was observed in the presence of Zn (II) and Cd (II) ions, while multipolar buds were observed in the presence of Cr (III), As (V), Ni (II), and Cd (II).…”

“…Heat shock also triggered a 15% decrease in cell size. Correspondingly, multiple structural changes in Y. lipolytica cells were observed after mild heat shock treatment (37 ℃, 60 min) (Biryukova et al 2011 ; Arinbasarova et al 2018 ). Those structural modifications comprised enlargement of mitochondria, enhanced number and enlargement of peroxisomes, formation of lipid and polyphosphate granules, as well as numerous globular surface structures, enriched in silicone.…”

“…Moreover, the exposure triggered the formation of globular structures of unknown nature on the cell wall surface. The following research on the modification of cellular envelope and intracellular structures in response to mild oxidative stress revealed that those surface globules contain silicone (Arinbasarova et al 2018 ). Those studies also evidenced the formation of the multi-layered plasma membrane and multiple membrane vesicles localized in proximity to the cell wall.…”

Conferring thermotolerant phenotype to wild‐type Yarrowia lipolytica improves cell growth and erythritol production

“…By engineering stress‐responsive promoter to dynamically control glutathione synthesis pathway and acetic acid degradation pathway, Qin et al (2020) has improved the stress tolerance of Saccharomyces cerevisiae and achieved normal cell growth and improved ethanol production under high temperature. Noticeably, it has been found that there are many globules on the cell wall of Y. lipolytica under heat stress and silicon is enriched (Qiu et al, 2019), however, the specific mechanism and how this contributes to the heat tolerance of Y. lipolytica strains is still unclear (Arinbasarova et al, 2018; Qiu et al, 2019).…”

Аккумуляция кремния как ответ дрожжей Yarrowia lipolytica на стрессовые воздействия

“…Аккумуляция кремния имеет место в стрессовых условиях и связана с образованием глобулярных структур. Образование глобулярных структур, содержащих кремний, происходит одновременно с другими изменениями ультраструктуры, в частности, модификациями клеточной оболочки, которая играет особую роль в сохранении формы и целостности клетки [6].…”