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Polyunsaturated fatty acids in the psychrophilic bacterium Shewanella gelidimarina ACAM 456(T): molecular species analysis of major phospholipids and biosynthesis of eicosapentaenoic acid

journal contribution
posted on 2023-05-16, 10:37 authored by David NicholsDavid Nichols, Peter Nichols, Russell, NJ, Noel DaviesNoel Davies, Thomas McMeekinThomas McMeekin
The production of eicosapentaenoic acid [20:5ω3; EPA] from Shewanella gelidimarina (ACAM 456(T)) was investigated with respect to growth temperature and growth on sole carbon sources. The percentage and quantitative yield of EPA remained relatively constant at all growth temperatures within or below the optimal growth temperature region. At higher growth temperatures, these values decreased greatly. Growth on differing sole carbon sources also influenced the percentage and amount of EPA produced, with the fatry acid composition influenced by provision of potential acyl chain primers as sole carbon sources. The highest amounts of EPA occurred from growth on propionic acid and L-leucine respectively, while the highest percentage of EPA occurred from growth on L-proline. Monounsaturated fatty acid components and EPA were concentrated in phosphatidylglycerol (PG), while the proportion of branched-chain fatty acids was elevated in phosphatidylethanolamine (PE); the two major phospholipid classes. Specific associations of EPA with other acyl chains were identified within cellular phospholipid classes. The association of EPA with 17:1 and 18:0 acyl chains in phospholipid species was specific to PG, whereas the association of EPA with i13:0/13:0 and 14:0/i14:0 was specific to PE. Such acyl chain 'tailoring' is indicative of the important role of EPA in bacterial membrane adaptive responses. EPA was also a large component (22%) of a non-esterified fatty acid (NEFA) fraction within the total lipid extract of the bacterium. This may point toward a particular role of NEFA in polyunsaturated fatty acid (PUFA) metabolism. The formation of EPA was investigated by labelling with L-[U-14 C]serine and sodium [1-14 C]acetate. The accumulation of radiolabel within unsaturated intermediates (di-, tri- and tetraunsaturated fractions) was low, indicating a rapid formation and derivatisation of these components. Similar results were found for the unsaturated fatty acid fractions of both PE and PG using sodium [1-14C]acetate radiolabel. The regulation of triunsaturated fatty acid components may be a potential control site in PUFA biosynthesis.

History

Publication title

Biochimica et Biophysica Acta - Lipids & Lipid Metabolism

Volume

1347

Issue

2-3

Pagination

164-176

ISSN

0005-2760

Department/School

Tasmanian Institute of Agriculture (TIA)

Publisher

Elsevier

Place of publication

Amsterdam

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the environmental sciences

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