Interestingly, the PE production was not affected in isolated bacteria, indicating that the symbiont maintained the biosynthetic route used for the formation of this phospholipid, which is usually the major one in the prokaryote envelope. This agreed with our previous works, which showed that PE is an essential constituent of the symbiotic bacterium membranes (Palmié-Peixoto et al., 2006). Once isolated from the protozoan, the symbiont is able to produce phospholipids, especially PE, independently of the host cell (Azevedo-Martins et al., 2007). However, it is noteworthy that the symbiosis in trypanosomatids is an obligatory relationship with extensive metabolic exchanges (reviewed
by Motta, 2010) and that the bacterium learn more may obtain part of PC or PC
precursors from the host (Azevedo-Martins et al., 2007). This, in part, explains why the effect of miltefosine in the phospholipid biosynthesis of the host protozoan directly affected the phospholipid content of the symbiotic bacterium. The mitochondrion is an organelle of symbiotic origin that imports most of its proteins and lipids from the cytoplasm (Timmis et al., 2004). In mitochondrial fractions obtained from host protozoa submitted to miltefosine treatment, the production of all types of phospholipids was strongly affected. It is well established that mitochondria participates in the synthesis of different lipids, such as the PE, which is generated via PS decarboxylase that converts this website phosphatidylserine (PS) into PE (Van Meer et al., 2008). Thus, it is worth considering that phospholipid biosynthesis inhibition in mitochondrion may affect its bioenergetics owing to lipid membrane change that would in turn affect the host metabolism and consequently the symbiont. Some aspects of lipid biosynthesis and composition were previously investigated in trypanosomatids using sterol biosynthesis inhibitors, such the as 22,26-azasterol, that act on the methyltransferase (24-SMT), a key enzyme in the biosynthesis of ergosterol and other 24-alkyl sterols, which are absent in mammalian cells (Urbina
et al., 1995, 1996). Such compounds also affect phospholipid production, by inhibiting PE and PC synthesis (Contreras et al., 1997; Urbina, 1997). When A. deanei was treated with azasterol, cells presented ultrastructural alterations as those reported in the present work. Furthermore, the sterol biosynthesis was blocked, and low rates of PC and increased levels of PE were observed, thus suggesting an inhibition of N-methyltransferase that converts PC into PE via the Greenberg pathway (Palmié-Peixoto et al., 2006). Interestingly, the PC content of the symbiotic bacterium was also reduced, reinforcing the idea that part of this phospholipid is obtained from the host cell (Azevedo-Martins et al., 2007).