Sterols of the Toxic Marine Dinoflagellate, Pyrodinium bahamense

Houle, Hannah M.; Lopez, Cary B.; Leblond, Jeffrey D.

doi:10.1111/jeu.12684

Cited by 11 publications

(10 citation statements)

References 29 publications

(64 reference statements)

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“…It could be possible that input variations of the C 31 stanol and stenol played a more important role than microbial alteration for the distributions of C 31 sterols. 4α-methylgorgostanol has been reported in a few dinoflagellate species belonging to the genera Peridinium, Alexandrium and Pyrodinium, (Atwood et al, 2014;Houle et al, In Press, and refs therein), and the mass spectra of the sterol we tentatively identified as 4α-methylgorgosterol is similar to 25 that reported for a sterol occurring in resting cysts but not in the motile cells of the dinoflagellate Peridinium umbonatum var. inaequale (Amo et al, 2010).…”

Section: Taphonomy Of Sterolssupporting

confidence: 81%

Sterol preservation in hypersaline microbial mats

Shen¹,

Thiel²,

Suarez-Gonzalez³

et al. 2019

Preprint

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Abstract. Microbial mats are self-sustaining benthic ecosystems composed of highly diverse microbial communities. It has been proposed that microbial mats were widespread in Proterozoic marine environments, prior to the emergence of bioturbating organisms at the Precambrian-Cambrian transition. One characteristic feature of Precambrian biomarker records is that steranes are typically absent or occur in very low concentrations. This has been explained by low eukaryotic source inputs, or degradation of primary produced sterols in benthic microbial mats (<q>mat-seal effect</q>). To better understand the preservational pathways of sterols in microbial mats we analysed freely extractable and carbonate-bound sterols as well as decalcified extraction residues in different layers of a recent calcifying mat (~&#8201;1500 years) from the hypersaline Lake 2 on the island of Kiritimati, Central Pacific. A variety of C27&#8211;C29 sterols and distinctive C31 4&#945;-methylsterols (4&#945;-methylgorgosterol and 4&#945;-methylgorgostanol, biomarkers for dinoflagellates) were detected in both lipid pools. These sterols most likely originated from organisms living in the water column and the upper mat layers. This autochthonous biomass experienced progressive microbial transformation and degradation in the microbial mat, as reflected by a significant drop in total sterols concentrations, up to 98&#8201;%, in the deeper layers, and a concomitant decrease in total organic carbon. Carbonate-bound sterols were generally low in abundance, suggesting that incorporation into the mineral matrix does not play a major role for the preservation of eukaryotic sterols in this mat. Likewise, pyrolysis revealed that steroids (i.e., including sterenes, steranes and sterols), in contrast to hopanoids, were not sequestered into insoluble organic matter which may give rise to a further bias in the preservation of steroids vs. hopanoids, particularly in the later stages of burial. While these findings argue for a strong 'mat-seal effect' in the mat studied, they markedly differ from recent findings made for another microbial mat growing in the near-by hypersaline Lake 22 on the same island, where sterols showed no systematic decrease with depth. The observed discrepancies in the taphonomic pathways of sterols in microbial mats from Kiritimati may be linked to multiple biotic and abiotic factors including salinity and periods of subaerial exposure, implying that caution has to be exercised in the interpretation of sterols distributions in modern and ancient microbial mat settings.

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Section: Taphonomy Of Sterolssupporting

confidence: 81%

Sterol preservation in hypersaline microbial mats

Shen¹,

Thiel²,

Suarez-Gonzalez³

et al. 2019

Preprint

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“…Of these, the mass spectra of sterols 17 and 20 matched those shown for these compounds in Houle et al . (2019 with discussion and references therein; all comparisons to other published data are made for mass spectra of sterols as their TMS‐ether derivatives); sterol 20 was observed previously in K. foliaceum by Alam et al . (1979).…”

Section: Resultsmentioning

confidence: 96%

Sterols of the ‘dinotom’ Durinskia baltica (Dinophyceae) are of dinoflagellate origin

Leblond

Vandergrift

2021

Phycological Research

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SUMMARY ‘Dinotoms’ are a relatively small group of dinoflagellates with aberrant tertiary plastids of diatom origin, thus differing from the majority of photosynthetic dinoflagellates which possess the carotenoid pigment peridinin and have secondary plastids of red algal origin. As part of our laboratory's continuing efforts to examine such unusual dinoflagellates in the search for clues to the evolution of their lipid compositions, we have examined the sterol composition of the dinotom Durinskia baltica. As such, we here compared its sterols to those of the previously examined dinotom, Kryptoperidinium foliaceum, more broadly to other photosynthetic, peridinin‐containing dinoflagellates, and to the diatom genus Nitzschia, which is the presumed ancestor of the D. baltica dinotom plastid. Sterols are ringed lipids, common to eukaryotes, thought to reinforce phospholipid bilayers. Many peridinin‐containing dinoflagellates have sterol compositions which are enriched by the presence of cholesterol (cholest‐5‐en‐3β‐ol) and 4α‐methyl‐substituted sterols such as dinosterol (4α,23,24‐trimethyl‐5α‐cholest‐22E‐en‐3β‐ol); this has also been found to be true for K. foliaceum despite its aberrant plastid ancestry. Our objective was to determine if this is also true for D. baltica as only the second dinotom to have its sterols characterized in detail, and to determine if there is any indication of prominent sterols which are uncommon to dinoflagellates, possibly originating from the diatom endosymbiont, as has been demonstrated previously with K. foliaceum and D. baltica chloroplast‐associated galactolipids of clear diatom origin. Our results demonstrate that like K. foliaceum, the major sterols of D. baltica are cholesterol, dinosterol, and other 4α‐methyl‐substituted sterols common to dinoflagellates. Although there were a number of minor sterols, none were found with obvious origin from the diatom endosymbiont, indicating that most originated with the dinoflagellate host itself, most likely before acquisition of the diatom tertiary plastid.

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“…A variety of C 27 -C 31 sterols have been observed in the studied mat, suggesting multiple sources mainly from algae, animals, fungi, and terrestrial plants [38,[71][72][73][74]. The major portion of GC-amenable hopanoids observed in the mat might be formed as the diagenetic products of bacteriohopanepolys (BHPs; [75][76][77]) through microbially-driven, progressive defunctionalisation.…”

Section: Lipid Preservation and Carbonate Precipitation Within The Matmentioning

confidence: 97%

Contrasting Modes of Carbonate Precipitation in a Hypersaline Microbial Mat and Their Influence on Biomarker Preservation (Kiritimati, Central Pacific)

2022

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Microbial mats represented the earliest complex ecosystems on Earth, since fossil mineralized examples (i.e., microbialites) date back to the Archean Eon. Some microbialites contain putative remains of organic matter (OM), however the processes and pathways that lead to the preservation of OM within microbialite minerals are still poorly understood. Here, a multidisciplinary study is presented (including petrographic, mineralogical and organic geochemical analyses), focusing on a modern calcifying mat from a hypersaline lake in the Kiritimati atoll (Central Pacific). The results show that this mat has a complex history, with two main growth phases under hypersaline conditions, separated by an interruption caused by desiccation and/or freshening of the lake. The mineral precipitates of the mat are predominantly aragonitic and two contrasting precipitation modes are observed: the main growth phases of the mat were characterized by the slow formation of irregular micritic particles with micropeloidal textures and subspherical particles, linked to the degradation of the exopolymer (EPS) matrix of the mat; whereas the interruption period was characterized by the rapid development of a thin yet laterally continuous crust composed of superposed fibrous aragonite botryoids that entombed their contemporaneous benthic microbial community. These two precipitation modes triggered different preservation pathways for the OM of the mat as the thin crust shows a particular lipid biomarker signature, different from that of other layers and the relatively rapid precipitation of the crust protecting the underlying lipids from degradation, causing them to show a preservation equivalent to that of a modern active microbial community, despite them being >1100 years old. Equivalent thin mineral crusts occur in other microbialite examples and, thus, this study highlights them as excellent targets for the search of well-preserved biomarker signatures in fossil microbialites. Nevertheless, the results of this work warn for extreme caution when interpreting complex microbialite biomarker signatures, advising combined petrographic, mineralogical and geochemical investigations for the different microbialite layers and mineral microfabrics.

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Sterols of the Toxic Marine Dinoflagellate, Pyrodinium bahamense

Cited by 11 publications

References 29 publications

Sterol preservation in hypersaline microbial mats

Sterol preservation in hypersaline microbial mats

Sterols of the ‘dinotom’ Durinskia baltica (Dinophyceae) are of dinoflagellate origin

Contrasting Modes of Carbonate Precipitation in a Hypersaline Microbial Mat and Their Influence on Biomarker Preservation (Kiritimati, Central Pacific)

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