Sterols of Ochromonas danica and Ochromonas malhamensis

Isopentenyl diphosphate, the universal isoprenoid precursor, can be produced by two different biosynthetic routes: either via the acetate/mevalonate (MVA) pathway, or via the more recently identified MVA-independent glyceraldehyde phosphate/pyruvate pathway. These two pathways are easily differentiated by incorporation of [1-13C]glucose and analysis of the resulting labelling patterns found in the isoprenoids. This method was successfully applied to several unicellular algae raised under heterotrophic growth conditions and allowed for the identification of the pathways that were utilized for isoprenoid biosynthesis. All isoprenoids examined (sterols, phytol, carotenoids) of the green algae Chlorella fusca and Chlamydomonas reinhardtii were synthesized via the GAP/pyruvate pathway, as in another previously investigated green alga, Scenedesmus obliquus, which was also shown in this study to synthesize ubiquinone by the same MVA-independent route. In the red alga Cyanidium caldarium and in the Chrysophyte Ochromonas danica a clear dichotomy was observed: as in higher plants, sterols were formed via the MVA route, whereas chloroplast isoprenoids (phytol in Cy. caldarium and O. danica and beta-carotene in O. danica) were synthesized via the GAP/pyruvate route. In contrast, the Euglenophyte Euglena gracilis synthesized ergosterol, as well as phytol, via the acetate/MVA route. Similar feeding experiments were performed with the cyanobacterium Synechocystis PCC 6714 using [1-13C]- and [6-13C]-glucose. The two isoprenoids examined, phytol and beta-carotene, were shown to have the typical labelling pattern derived from the GAP/pyruvate route.

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“…Eu. gracilis contained, as expected, ergosterol [32] and O. danica contained poriferasterol and 7-dehydroporiferasterol [33]. In Cy.…”

Section: Isolation and Identification Of Isoprenoidssupporting

confidence: 81%

Distribution of the mevalonate and glyceraldehyde phosphate/pyruvate pathways for isoprenoid biosynthesis in unicellular algae and the cyanobacterium Synechocystis PCC 6714

Disch

Schwender

Müller

et al. 1998

Biochemical Journal

191

123

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“…The two C-24 epimers of 24-ethylcholesta-5,22-dien-3b-ol-poriferasterol (24b) and stigmasterol (24a)-could not be fully separated on the gas chromatograph-flame ionization detector and gas chromatograph-mass spectrometer systems used; therefore, the stereochemistry of the ethyl group at C-24 was not defined. The presence of poriferasterol in the related chrysomonad Ochromonas (Gershengorn et al 1968) suggests that the 24b configuration of 24-ethylcholesta-5,22-dien-3b-ol is also present in Paraphysomonas sp. Another sterol found in Paraphysomonas sp.…”

Section: Resultsmentioning

confidence: 99%

Trophic upgrading of autotrophic picoplankton by the heterotrophic nanoflagellate Paraphysomonas sp.

Bec

Martin‐Creuzburg

Elert

2006

Limnology & Oceanography

101

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We investigated whether trophic repackaging of autotrophic picoplankton by phagotrophic protists is associated with an improvement in food quality for the metazooplankton Daphnia magna (i.e., whether trophic upgrading occurs in this system). The nutritional value of the autotrophic species Microcystis aeruginosa PCC7806, Synechococcus sp. strain BO8809, Synechococcus elongatus SAG 89.79, and Choricystis minor KR1988/ 8, and of the heterotrophic nanoflagellate Paraphysomonas sp. grown on these different picoplanktonic species was evaluated in standardized growth experiments with D. magna. In order to investigate the functional role of the flagellate in the simplified autotrophic picoplankton-Daphnia food chain, Paraphysomonas sp. was grown on the different picoplanktonic organisms and subsequently separated from the food items before being fed to D. magna. The presence of Paraphysomonas sp. as an intermediary trophic step enhanced somatic growth and reproduction of D. magna. Supplementation of Synechococcus sp. with lipids from Paraphysomonas sp. (grown on Synechococcus sp.) revealed that trophic upgrading of autotrophic picoplankton is due to the additional lipids present in the flagellate. Paraphysomonas sp. synthesized polyunsaturated fatty acids and sterols de novo, which most likely explains the trophic upgrading. Paraphysomonas sp. also improved the food quality of M. aeruginosa PCC7806, which is toxic for D. magna. The heterotrophic flagellate Paraphysomonas sp. is capable of trophically upgrading a poor quality food source not only by producing essential lipids, but also by detoxifying the cyanobacterial food organism.

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“…For example, a high predominance of 24-ethylcholesterol is found in the diatoms Asterionella glacialis (Jones et al 1987), Haslea ostrearia and Amphiprora hyalina (Barrett et al 1995), the raphidophyte Olisthodiscus luteus (Patterson and van Valkenburg 1990) and several freshwater chrysophytes (Cranwell et al 1988). Chrysophytes such as Ochromonas contain mainly 24-ethylcholesta-5,22E-dien-3b-ol (Gershengorn et al 1968), but here the epimer is poriferasterol (24b) rather than stigmasterol (24a). Many cyanobacteria have also been reported to contain a high proportion of 24-ethylcholesterol in the sterol mixture, although concentrations per cell are low (Paoletti et al 1976;Volkman 1986) and some reports seem doubtful (see later)…”

Section: -Desmethyl-d 5 -Sterols In Microalgaementioning

confidence: 99%

Sterols in microorganisms

Volkman

2003

Appl Microbiol Biotechnol

737

478

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Sterols are vital components of all eukaryotic cells. This review describes the variety of sterol structures found in microalgae, yeasts, fungi, protozoans and microheterotrophs. Reports of the occurrence of sterols in prokaryotic cells are critically assessed. Methylotrophic bacteria contain unusual 4-methylsterols, but reports of 4-desmethyl sterols in cyanobacteria and other bacteria are limited and many of these seem dubious. Possible application areas for sterols derived from mass culture of microalgae and other microorganisms are highlighted.

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Sterols of Ochromonas danica and Ochromonas malhamensis

Abstract: The sterols of Ochromonas danica have been identified as ergosterol, brassicasterol, 22-dihydrobrassicasterol, clionasterol, poriferasterol, and probably 7-dehydroporiferasterol. By contrast Ochromonas mal-

Cited by 83 publications

References 48 publications

Distribution of the mevalonate and glyceraldehyde phosphate/pyruvate pathways for isoprenoid biosynthesis in unicellular algae and the cyanobacterium Synechocystis PCC 6714

Distribution of the mevalonate and glyceraldehyde phosphate/pyruvate pathways for isoprenoid biosynthesis in unicellular algae and the cyanobacterium Synechocystis PCC 6714

Trophic upgrading of autotrophic picoplankton by the heterotrophic nanoflagellate Paraphysomonas sp.

Sterols in microorganisms

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