Gas chromatography-mass spectrometry selected ion monitoring and gas chromatography-tandem mass spectrometry selected reaction monitoring analyses of mono-, di- and tri-unsaturated C highly branched isoprenoid alkene biomarkers in sea ice and sediment samples: A comparative study.

Rationale: The efficiency of selected ion monitoring (SIM) and selected reaction monitoring (SRM) analyses for the quantification of three mono-, di- and tri-unsaturated highly branched isoprenoid (HBI) alkenes (IP , IPSO and HBI III, respectively), often used as proxies for the occurrence of Arctic and Antarctic sea ice or the adjacent open waters, was compared.

Methods: Gas chromatography (GC)-mass spectrometry (MS)/SIM and GC/MS/MS/SRM analyses were carried out on dilute solutions made from purified standards of these three HBIs, and then on hydrocarbon fractions of several sediment and sea ice sample extracts. More efficient and specific SRM transitions were selected after collision-induced dissociation of each precursor ion at different collision energies.

Singlet oxygen-induced alteration of bacteria associated with phytodetritus: Effect of irradiance.

Contrasting irradiation of senescent cells of the diatom Thalassiosira sp. in association with the bacterium Pseudomonas stutzeri showed the effect of intensity of irradiance on the transfer of singlet oxygen ( O ) to bacteria attached to phytoplanktonic cells. Under low irradiances, O is produced slowly, favors the oxidation of algal unsaturated lipids (photodynamic effect), and limits O transfer to attached bacteria.

Cellular Damage of Bacteria Attached to Senescent Phytoplankton Cells as a Result of the Transfer of Photochemically Produced Singlet Oxygen: A Review.

Several studies set out to explain the presence of high proportions of photooxidation products of cis-vaccenic acid (generally considered to be of bacterial origin) in marine environments. These studies show that these oxidation products result from the transfer of singlet oxygen from senescent phytoplankton cells to the bacteria attached to them in response to irradiation by sunlight. This paper summarizes and reviews the key findings of these studies, i.

Use of Trifluoro-Acetate Derivatives for GC-MS and GC-MS/MS Quantification of Trace Amounts of Stera-3β,5α,6β-Triols (Tracers of Δ-Sterol Autoxidation) in Environmental Samples.

Stera-3β,5α,6β-triols make useful tracers of the autoxidation of Δ-sterols. These compounds are generally analyzed using gas chromatography-mass spectrometry (GC-MS) after silylation. Unfortunately, the 5α hydroxyl groups of these compounds, which are not derivatized by conventional silylation reagents, substantially alter the chromatographic properties of these derivatives, thus ruling out firm quantification of trace amounts.

Use of Gas Chromatography-Mass Spectrometry Techniques (GC-MS, GC-MS/MS and GC-QTOF) for the Characterization of Photooxidation and Autoxidation Products of Lipids of Autotrophic Organisms in Environmental Samples.

This paper reviews applications of gas chromatography-mass spectrometry techniques for the characterization of photooxidation and autoxidation products of lipids of senescent phototrophic organisms. Particular attention is given to: (i) the selection of oxidation products that are sufficiently stable under environmental conditions and specific to each lipid class and degradation route; (ii) the description of electron ionization mass fragmentation of trimethylsilyl derivatives of these compounds; and (iii) the use of specific fragment ions for monitoring the oxidation of the main unsaturated lipid components of phototrophs. The techniques best geared for this task were gas chromatography-quadrupole-time of flight to monitor fragment ions with very high resolution and accuracy, and gas chromatography-tandem mass spectrometry to monitor very selective transitions in multiple reaction monitoring mode.

Electron ionization mass spectrometric fragmentation and multiple reaction monitoring quantification of ferulic and p-coumaric acid trimethylsilyl derivatives in deposited atmospheric particles.

Rationale: Ferulic and p-coumaric acids are important biological and structural components of plant cell walls and possess antioxidant and antimicrobial properties. These phenolic acids are widespread in environmental samples. However, when they are present at very low concentrations or in very complex lipid extracts, their identification and quantification can be challenging.

Use of Stress Signals of Their Attached Bacteria to Monitor Sympagic Algae Preservation in Canadian Arctic Sediments.

Based on the strong aggregation of sympagic (ice-associated) algae and the high mortality or inactivity of bacteria attached to them, it was previously hypothesized that sympagic algae should be significant contributors to the export of carbon to Arctic sediments. In the present work, the lipid content of 30 sediment samples collected in the Canadian Arctic was investigated to test this hypothesis. The detection of high proportions of vaccenic fatty acid (resulting from isomerase (CTI) activity of bacteria under hypersaline conditions) and 10-hydroxyhexadec-8()-enoic acid (resulting from 10-DOX bacterial detoxification activity in the presence of deleterious free palmitoleic acid) confirmed: (i) the strong contribution of sympagic material to some Arctic sediments, and (ii) the impaired physiological status of its associated bacterial communities.

Type II photosensitized oxidation in senescent microalgal cells at different latitudes: Does low under-ice irradiance in polar regions enhance efficiency?

Comparison of Type II photosensitized oxidation of lipids (the photodynamic effect) and photodegradation of chlorophyll (sensitizer photobleaching) in samples of particulate matter collected previously from locations representing a diverse range of latitudes reveals an enhancement of the photooxidation of lipids at the expense of chlorophyll photodegradation in the polar regions. The efficiency of the photodynamic effect appears to be particularly high in sinking particles collected under sea ice and is attributed to the rapid settling of highly aggregated sympagic algae to depths of low light transmission favouring the photodynamic effect at the expense of photobleaching of the sensitizer. Paradoxically, the low efficiency of Type II photosensitized oxidation of lipids observed in temperate and equatorial regions is associated with high solar irradiances in these regions.

Viability and stress state of bacteria associated with primary production or zooplankton-derived suspended particulate matter in summer along a transect in Baffin Bay (Arctic Ocean).

In the framework of the GreenEdge Project (whose the general objective is to understand the dynamic of the phytoplankton spring bloom in Arctic Ocean), lipid composition and viability and stress state of bacteria were monitored in sea ice and suspended particulate matter (SPM) samples collected in 2016 along a transect from sea ice to open water in Baffin Bay (Arctic Ocean). Lipid analyses confirmed the dominance of diatoms in the bottommost layer of ice and suggested (i) the presence of a strong proportion of micro-zooplankton in SPM samples collected at the western ice covered St 403 and St 409 and (ii) a high proportion of macro-zooplankton (copepods) in SPM samples collected at the eastern ice covered St 413 and open water St 418. The use of the propidium monoazide (PMA) method allowed to show a high bacterial mortality in sea ice and in SPM material collected in shallower waters at St 409 and St 418.

Electron ionization mass spectrometric fragmentation and detection of autoxidation products of 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5-ene in Arctic sediments.

Rationale: Some highly branched isoprenoid (HBI) alkenes are commonly used as proxies for palaeoceanographic reconstructions. However, there is a need to identify compounds that are sufficiently stable and abundant to be used as tracers of HBI oxidation in sediments. 2,6,10,14-Tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5(Z/E)-en-4-ols resulting from 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5-ene appear to be useful for this purpose.

Biotic and abiotic degradation of Δ-sterols in senescent Mediterranean marine and terrestrial angiosperms.

This work used Δ-sterols and their degradation products to compare the efficiency of biotic and abiotic degradation processes in senescent Mediterranean marine (Posidonia oceanica) and terrestrial (Quercus ilex and Smilax aspera) angiosperms. Type II photosensitized oxidation processes appeared to be more efficient in P. oceanica than in Q.

EIMS Fragmentation and MRM quantification of autoxidation products of α- and β-amyrins in natural samples.

Rationale: Riverine particulate organic matter is generally considered to be refractory with respect to further decomposition in the ocean. In order to check the validity of this paradigm, there is a real need for tracers sufficiently stable and specific to monitor the degradation of terrestrial higher plant material in the environment. 3β-hydroxy-urs-12-en-11-one and 3β-hydroxy-olean-12-en-11-one (autoxidation products of α- and β-amyrin) were previously proposed for such use.

Electron ionization mass spectrometry fragmentation and multiple reaction monitoring quantification of bacterial metabolites of the sea ice biomarker proxy IP in Arctic sediments.

Rationale: 3,9,13-Trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid appear to be produced during the bacterial metabolism of IP , a highly branched isoprenoid lipid often employed for past Arctic sea ice reconstruction. Characterization and quantification of these metabolites in sediments are essential to determine if bacterial degradation may exert a significant influence on IP -based palaeo sea ice reconstructions.

Methods: Electron ionization mass spectrometry (EIMS) fragmentation pathways of 3,9,13-trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid trimethylsilyl (TMS) derivatives were investigated.

Electron ionization mass spectrometric fragmentation and multiple reaction monitoring quantification of trimethylsilyl derivatives of cucurbic acid and its 6,7-stereoisomers.

Rationale: Isomeric cucurbic acids derive from the reduction of the keto group of jasmonic acids. These growth regulators are natural constituents of various higher plants and fungi. Elucidation of electron ionization mass spectrometry (EIMS) fragmentation pathways of the trimethylsilyl (TMS) derivatives of the different stereoisomers is essential for their characterization and quantification in natural samples.

Paradoxical effects of temperature and solar irradiance on the photodegradation state of killed phytoplankton.

The aim of this paper was to study the effects of temperature and irradiance on the photodegradation state of killed phytoplankton cells. For this purpose, killed cells of the diatom Chaetoceros neogracilis RCC2022 were irradiated (photosynthetically active radiation) at 36 and 446 J · s(-1)  · m(-2) (for the same cumulative dose of irradiation energy) and at two temperatures (7°C and 17°C). Analyses of specific lipid tracers (fatty acids and sterols) revealed that low temperatures and irradiances increased photooxidative damages of monounsaturated lipids (i.

EIMS Fragmentation Pathways and MRM Quantification of 7α/β-Hydroxy-Dehydroabietic Acid TMS Derivatives.

EI mass fragmentation pathways of TMS derivatives οf 7α/β-hydroxy-dehydroabietic acids resulting from NaBH(4)-reduction of oxidation products of dehydroabietic acid (a component of conifers) were investigated and deduced by a combination of (1) low energy CID-GC-MS/MS, (2) deuterium labeling, (3) different derivatization methods, and (4) GC-QTOF accurate mass measurements. Having identified the main fragmentation pathways, the TMS-derivatized 7α/β-hydroxy-dehydroabietic acids could be quantified in multiple reaction monitoring (MRM) mode in sea ice and sediment samples collected from the Arctic. These newly characterized transformation products of dehydroabietic acid constitute potential tracers of biotic and abiotic degradation of terrestrial higher plants in the environment.

Dynamic of bacterial communities attached to lightened phytodetritus.

The effects of singlet oxygen ((1)O2) transfer to bacteria attached on phytodetritus were investigated under laboratory-controlled conditions. For this purpose, a nonaxenic culture of Emiliania huxleyi in late stationary phase was studied for bacterial viability. Our results indicated that only 9 ± 3% of attached bacteria were alive compared to 46 ± 23% for free bacteria in the E.

Electron ionization mass spectrometry fragmentation pathways of trimethylsilyl derivatives of isomeric allylic alcohols derived from HBI alkene oxidation.

Rationale: C25 tri-unsaturated highly branched isoprenoid (HBI) alkenes are produced by a number of marine diatoms around the world yet are very easily oxidized during senescence to yield several isomeric allylic 9-hydroperoxides. Elucidation of the electron ionization mass spectrometry (EIMS) fragmentation pathways of the trimethylsilyl (TMS) derivatives of the alcohols (obtained by reduction of the corresponding 9-hydroperoxides) is essential for their characterization and quantification in natural samples.

Methods: EIMS fragmentation pathways of TMS derivatives of isomeric allylic alcohols resulting from NaBH4 reduction of photo- and autoxidation products of HBI alkenes were investigated.

Elucidation of electron ionization mass spectrometric fragmentation pathways of trimethylsilyl ether derivatives of vicinal diols deriving from haplamine by collision-induced dissociation gas chromatography/tandem mass spectrometry and ¹⁸O labelling.

Rationale: Formation of vicinal diols was observed after in vitro and in vivo studies of the natural product haplamine (9-methoxy-2,2-dimethyl-2,6-dihydropyrano[3,2-c]quinolin-5-one). These compounds, identified as trans- and cis-3,4-dihydroxy-9-methoxy-2,2-dimethyl-2,3,4,6-tetrahydropyrano[3,2-c]quinolin-5-ones and trans- and cis-3,4,9-trihydroxy-2,2-dimethyl-2,3,4,6-tetrahydropyrano[3,2-c]quinolin-5-ones, have a potential interest in oncology. It is therefore essential to elucidate their electron ionization mass spectrometric (EIMS) fragmentation pathways.

Photochemical production and behavior of hydroperoxyacids in heterotrophic bacteria attached to senescent phytoplanktonic cells.

The photooxidation of cellular monounsaturated fatty acids was investigated in senescent phytoplanktonic cells (Emiliania huxleyi) and in their attached bacteria under laboratory controlled conditions. Our results indicated that UV-visible irradiation of phytodetritus induced the photooxidation of oleic (produced by phytoplankton and bacteria) and cis-vaccenic (specifically produced by bacteria) acids. These experiments confirmed the involvement of a substantial singlet oxygen transfer from senescent phytoplanktonic cells to attached bacteria, and revealed a significant correlation between the concentration of chlorophyll, a photosensitizer, in the phytodetritus and the photodegradation state of bacteria.

Anaerobic oxidation of n-alkenes by sulphate-reducing bacteria from the genus Desulfatiferula: n-ketones as potential metabolites.

Two alkene-degrading sulphate-reducing bacteria from the genus Desulfatiferula (Desulfatiferula olefinivorans strain LM2801(T) and Desulfatiferula sp. strain BE2801) were investigated for their 1-alkene metabolism. Their total cellular fatty acids were predominantly C-even when they were grown on C-even 1-alkene (1-hexadecene), whereas a mixture of fatty acids with C-odd or C-even carbon chains predominated when cells were grown on C-odd 1-alkene (1-pentadecene).

Production of pristane and phytane in the marine environment: role of prokaryotes.

This paper reviews studies dealing with the formation of pristane and phytane in the marine environment and focuses on the role played by prokaryotes in these processes. Prokaryotes may notably: (i) contribute to the formation of pristane during invertebrate feeding; (ii) hydrogenate isomeric pristenes and phytenes arising from degradation of the chlorophyll phytyl side-chain and/or α-tocopherol (vitamin E) to pristane and phytane, respectively; and (iii) convert trimeric oxidation products of α-tocopherol (produced abiotically in the water column and in the oxic zone of sediments) to pristane. Moreover, thermal maturation of isoprenoid components of archaea (isopranyl glyceryl ethers) also constitutes another potential source of pristane and phytane in thermally mature sediments.

Potential alteration of U37K' paleothermometer due to selective degradation of alkenones by marine bacteria isolated from the haptophyte Emiliania huxleyi.

The unsaturation ratio of C(37) alkenones (U(37)(K')) produced by haptophyte microalgae such as Emiliania huxleyi is often used as proxy for past sea surface temperature. In this study, 29 bacterial strains were isolated from cultures of the strain E. huxleyi TWP1.