## 3 Discussion
The \"model of secretory vesicles\" based on the development of Lb from the secretory vesicles filled with TAGs is one of the possible models for forming Lb in a yeast cell. Lbs are usually about 300-400 nm in diameter and covered with a PL monolayer containing few proteins [39], mainly the enzymes of lipid metabolism [40]. Of note, the ratio of TAGs to EST in Lbs from _S. cerevisiae_ is usually 1:1 [41], and their TAGs core is surrounded by several EST envelopes [42]. In our studies, we found TAGs as a minority (about 4% of the total lipids) only in the mitochondria of the logarithmic growth stage (Figure 2A). During cultivation, they were replaced by FFAs with the highest level in the 24-h stage. DAGs kept up at about the same level (about 10-15%) throughout the experiment. It is probable that such an alteration in the storage lipids composition in the mitochondria is due to the depletion of the storage lipid resource during growth. In a yeast cell, there are three main pathways for synthesis of DAGs: (1) PA removal by phosphatidate phosphatase (_PAH1_); (2) degradation of phospholipids by phospholipases (_LRO1_, _DGA1_, _ARE1_/2); and (3) deacetylation of TAGs (_TGL2/3/4/5_, _AYR1_) [39]. We suppose that upon intensive growth, the third pathway of DAGs formation seems preferable, taking into account the disappearance of TAGs in the stationary growth phase. At the same time, the high FFAs level in the _E. magnusii_ mitochondria could be related to the presence of a minority of EST (Figure 2A). The FFAs synthesis in yeast occurs via three main pathways: (1) de novo synthesis, (2) the complex and storage lipid degradation, and (3) external uptake [39]. Taking our data altogether, including the growing conditions of _E. magnusii_, we posit that in our experiments, the FFAs synthesis occurs de novo in the cytosol and mitochondria with a concurrent elongation and desaturation in the ER. The initial stage of the FFA synthesis is triggered by the acetyl-CoA carboxylase (the cytosolic enzyme is encoded by _ACC1_, the mitochondrial one is by _HFA1_). In this reaction, acetyl-CoA is carboxylated and forms malonyl-CoA serving as a two-carbon building block for the next FFAs synthesis reactions [39]. Figure 7: Image of _E. magnusii_ yeast cells in the logarithmic (**A**) and early stationary growth phases (**B**). Nu—nucleus; Mt—mitochondria; Lb—lipid bodies. CL performs a lot of cell functions, being associated with all the major proteins of the mitochondrial respiratory system, and thereby increases the efficacy of the electron flux and the ADP/ATP exchange [40]. This PL corrects the catalytic activity and stability of the interactive proteins [41], is crucial for the biogenesis of mitochondria proteins [42], promotes mitochondrial fission/fusion [38], and participates in the cristate structure and morphology formation [43]. According to some researchers' data [43; 44], the CL amount in the mitochondrial fraction of _S. cerevisiae_ reaches 7.2% of the total membrane PL one, while for the mitochondria from _E. magnusii_, its level was much higher. In the logarithmic growth stage, the CL fraction made up about 50%, and in the stationary ones, it was not less than 18-20% (Figure 3A). It is probable that such a permanently high level of the CL fraction provides the high mitochondrial activity. In 2012, _[PERSON]_ [45] showed that CL-rich areas of the outer mitochondrial membrane exhibited a higher activity of the mitochondrial VDAC porin involved in eliminating the ROS from the mitochondria. The CL fatty acids composition impacts VDAC activity greatly. This fact can be considered as the third most important point of the lipid composition adaptation in the yeast mitochondrial upon long-term cultivation. Nevertheless, it is noteworthy that the PLs composition of the mitochondria in _E. magnusii_ differs significantly from that in _Saccharomyces_, where the dominating PLs fractions were PC, PE, and PL. Their shares made up 40.4% (PC), 26.7% (PE), and 14.6% (PI) [46; 47]. In the _E.