The Importance of Glycerophospholipid Production to the Mutualist Symbiosis of Trypanosomatids

The symbiosis in trypanosomatids is a mutualistic relationship characterized by extensive metabolic exchanges between the bacterium and the protozoan. The symbiotic bacterium can complete host essential metabolic pathways, such as those for heme, amino acid, and vitamin production. Experimental assays indicate that the symbiont acquires phospholipids from the host trypanosomatid, especially phosphatidylcholine, which is often present in bacteria that have a close association with eukaryotic cells. In this work, an in-silico study was performed to find genes involved in the glycerophospholipid (GPL) production of Symbiont Harboring Trypanosomatids (SHTs) and their respective bacteria, also extending the search for trypanosomatids that naturally do not have symbionts. Results showed that most genes for GPL synthesis are only present in the SHT. The bacterium has an exclusive sequence related to phosphatidylglycerol production and contains genes for phosphatidic acid production, which may enhance SHT phosphatidic acid production. Phylogenetic data did not indicate gene transfers from the bacterium to the SHT nucleus, proposing that enzymes participating in GPL route have eukaryotic characteristics. Taken together, our data indicate that, differently from other metabolic pathways described so far, the symbiont contributes little to the production of GPLs and acquires most of these molecules from the SHT.