Issue 4, 2016

Probing fatty acid metabolism in bacteria, cyanobacteria, green microalgae and diatoms with natural and unnatural fatty acids

Abstract

In both eukaryotes and prokaryotes, fatty acid synthases are responsible for the biosynthesis of fatty acids in an iterative process, extending the fatty acid by two carbon units every cycle. Thus, odd numbered fatty acids are rarely found in nature. We tested whether representatives of diverse microbial phyla have the ability to incorporate odd-chain fatty acids as substrates for their fatty acid synthases and their downstream enzymes. We fed various odd and short chain fatty acids to the bacterium Escherichia coli, cyanobacterium Synechocystis sp. PCC 6803, green microalga Chlamydomonas reinhardtii and diatom Thalassiosira pseudonana. Major differences were observed, specifically in the ability among species to incorporate and elongate short chain fatty acids. We demonstrate that E. coli, C. reinhardtii, and T. pseudonana can produce longer fatty acid products from short chain precursors (C3 and C5), while Synechocystis sp. PCC 6803 lacks this ability. However, Synechocystis can incorporate and elongate longer chain fatty acids due to acyl–acyl carrier protein synthetase (AasS) activity, and knockout of this protein eliminates the ability to incorporate these fatty acids. In addition, expression of a characterized AasS from Vibrio harveyii confers a similar capability to E. coli. The ability to desaturate exogenously added fatty acids was only observed in Synechocystis and C. reinhardtii. We further probed fatty acid metabolism of these organisms by feeding desaturase inhibitors to test the specificity of long-chain fatty acid desaturases. In particular, supplementation with thia fatty acids can alter fatty acid profiles based on the location of the sulfur in the chain. We show that coupling sensitive gas chromatography mass spectrometry to supplementation of unnatural fatty acids can reveal major differences between fatty acid metabolism in various organisms. Often unnatural fatty acids have antibacterial or even therapeutic properties. Feeding of short precursors now gives us easy access to these extended molecules.

Graphical abstract: Probing fatty acid metabolism in bacteria, cyanobacteria, green microalgae and diatoms with natural and unnatural fatty acids

Supplementary files

Article information

Article type
Paper
Submitted
20 Du 2015
Accepted
05 Cʼhwe. 2016
First published
05 Cʼhwe. 2016

Mol. BioSyst., 2016,12, 1299-1312

Probing fatty acid metabolism in bacteria, cyanobacteria, green microalgae and diatoms with natural and unnatural fatty acids

J. Beld, R. Abbriano, K. Finzel, M. Hildebrand and M. D. Burkart, Mol. BioSyst., 2016, 12, 1299 DOI: 10.1039/C5MB00804B

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