Abstract
Oleaginous microorganisms represent possible platforms for the sustainable production of oleochemicals and biofuels due to their metabolic robustness and the possibility to be engineered. Streptomyces coelicolor is among the narrow group of prokaryotes capable of accumulating triacylglycerol (TAG) as carbon and energy reserve. Although the pathways for TAG biosynthesis in this organism have been widely addressed, the set of genes required for their breakdown have remained elusive so far. Here, we identified and characterized three gene clusters involved in the β-oxidation of fatty acids (FA). The role of each of the three different S. coelicolor FadAB proteins in FA catabolism was confirmed by complementation of an Escherichia coliΔfadBA mutant strain deficient in β-oxidation. In S. coelicolor, the expression profile of the three gene clusters showed variation related with the stage of growth and the presence of FA in media. Flux balance analyses using a corrected version of the current S. coelicolor metabolic model containing detailed TAG biosynthesis reactions suggested the relevance of the identified fadAB genes in the accumulation of TAG. Thus, through the construction and analysis of fadAB knockout mutant strains, we obtained an S. coelicolor mutant that showed a 4.3-fold increase in the TAG content compared to the wild type strain grown under the same culture conditions.
Highlights
Species of the genus Streptomyces produce the vast majority of clinically used antibiotics and belong to the narrow group of prokaryotes capable of accumulating triacylglycerol (TAG) (Olukoshi and Packter, 1994; Gago et al, 2011; Alvarez, 2016), which is a metabolic feature typically found in eukaryotes
These two clusters are surrounded by putative fatty acids (FA) metabolism-related genes (Figure 1A)
M. tuberculosis possesses 35 transcriptionally active fadE genes, which are believed to be involved in the catabolism of structurally diverse FA during growth on different environments (Schnappinger et al, 2003)
Summary
Species of the genus Streptomyces produce the vast majority of clinically used antibiotics and belong to the narrow group of prokaryotes capable of accumulating triacylglycerol (TAG) (Olukoshi and Packter, 1994; Gago et al, 2011; Alvarez, 2016), which is a metabolic feature typically found in eukaryotes. When present in the medium, glucose stimulates the degradation of long-chain FA partly by increasing the uptake rate of FA and the activity of acyl-CoA synthetase (Banchio and Gramajo, 1997) As mentioned, this microorganism utilizes FA to synthesize membrane phospholipids and to be incorporated into neutral lipid storage compounds, such as TAG (Olukoshi and Packter, 1994; Alvarez, 2016). Other pathways in this bacterium have been suggested to substantially contribute to TAG biosynthesis (Arabolaza et al, 2008)
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