Genetic suppression of lethal mutations in fatty acid biosynthesis mediated by a secondary lipid synthase

Appl Environ Microbiol. 2021 Apr 9:AEM.00035-21. doi: 10.1128/AEM.00035-21. Online ahead of print.ABSTRACTThe biosynthesis and incorporation of polyunsaturated fatty acids into phospholipid membranes is a unique feature of certain marine Gammaproteobacteria inhabiting high-pressure and/or low temperature environments. In these bacteria, monounsaturated and saturated fatty acids are produced via the classical dissociated Type II fatty acid synthase mechanism, while omega-3 polyunsaturated fatty acids such as EPA (20:5n-3) and DHA (22:6n-3) are produced by a hybrid polyketide/fatty acid synthase - encoded by the pfa genes - also referred to as the secondary lipid synthase mechanism. In this work, phenotypes associated with partial or complete loss of monounsaturated biosynthesis are shown to be compensated for by several-fold increased production of polyunsaturated fatty acids in the model marine bacterium Photobacterium profundum SS9. One route to suppression of these phenotypes could be achieved by transposition of insertion sequences within or upstream of the fabD, malonyl CoA-acyl carrier protein transacylase, coding sequence. Genetic experiments in this strain indicated that fabD is not an essential gene, yet mutations in fabD and pfaA are synthetically lethal. Based on these results, we speculated that the malonyl-CoA transacylase domain within PfaA compensates for loss of FabD activity. Heterologous expression of either pfaABCD from P. profundum SS9 or pfaABCDE from Shew...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Source Type: research