Evidence for substantial intramolecular heterogeneity in the stable carbon isotopic composition of phytol in photoautotrophic organisms

Abstract

The ubiquitous isoprenoid phytol was isolated from a range of algae, terrestrial plants and a bacterium and its two terminal carbon atoms were quantitatively removed by chemical oxidation. The product, 6,10,14-trimethylpentadecan-2-one, was depleted in 13 C by 1-4‰ relative to the parent phytol. This difference is significant, and indicates that the pathway for biosynthesis of phytol induces substantial intramolecular stable carbon isotopic fractionations. The nature and magnitude of the fractionations suggest strongly that it is associated both with the biosynthesis of isopentenyl pyrophosphate via the 2-C-methylerythritol-4-phosphate pathway and with the formation of carotenoids and phytol from geranyl-geraniolphosphate. As a result of these large, intramolecular isotopic differences, diagenetic products formed by loss of C, such as pristane, may be naturally depleted in 13 C by several permil relative to phytane.

Geochemically distinct carbon isotope distributions in Allochromatium vinosum DSM 180T grown photoautotrophically and photoheterotrophically

“…5‰ depleted in 13 C relative to FA in the photoheterotrophic culture (Table , Figure ). The 2‰ enrichment relative to n ‐alkyl lipids in the photoautotrophic culture is consistent with other reports of CO 2 ‐fixing organisms (Hayes, ; Sakata et al., ; Schouten et al., , ). The only report of which we are aware that compares phytol 13 C patterns for photoheterotrophy versus photoautotrophy is for the related taxon, Chromatium tepidum (Madigan, Takigiku, Lee, Gest, & Hayes, ).…”

“…Other discussions of the relative 13 C patterns between isoprenoids and biomass have focused largely on eukaryotic algae (e.g., Schouten et al., , ). Although more complicated to interpret than bacteria, some of the same principles may apply.…”

Predominance of archaea-derived hydrocarbons in an Early Triassic microbialite

“…5 and Table 1), which might occur naturally due to the intramolecular isotopic heterogeneity of the parent compound, phytol, during loss of a C atom (cf. Schouten et al, 2008); an analogous effect has been observed for 6,10,14-trimethylpentadecan-2-one, which was depleted in 13 C relative to its parent compound, phytol, by 1-4‰ (cf. Schouten et al, 2008).…”

“…Schouten et al, 2008); an analogous effect has been observed for 6,10,14-trimethylpentadecan-2-one, which was depleted in 13 C relative to its parent compound, phytol, by 1-4‰ (cf. Schouten et al, 2008). Plausible source organisms for the C 21-25 head-to-tail linked isoprenoid hydrocarbons are halophilic archaea (e.g.…”

Phytol in a pharma-medico-stance

“…PYT moieties are formed both through MVA (mevalonic acid) [32e34] and MEP (2-C-methylerythritol-4-phosphate) pathways [29,35] (Fig. 4).…”