Isoprenoid Hydrocarbons Research Articles

Reinterpretation of lycopane as a biomarker of archaea based on its occurrence in authigenic sulfur-bearing carbonates

The tail-to-tail linked C40 isoprenoid hydrocarbon lycopane is a biomarker found in a wide variety of environments and in some extremophilic archaea but is also a possibly degradation product of a carotenoid (bacterioruberin) as well as plants (various lycopenes) and green algae (lycopadiene). Although potential producers are known, the source of lycopane in water-column and sedimentary environments is commonly ambiguous. In this study, the occurrence of 13C-depleted lycopane (δ13C = −114 to −106 ‰) in authigenic, sulfur-bearing carbonates from Monte Palco (Sicily) is used to re-evaluate the environmental significance of lycopane. In the Monte Palco authigenic carbonates, lycopane is accompanied by other, similarly 13C-depleted apolar isoprenoids such as PMI, squalane, and sulfurized homologues, including a tail-to-tail linked C35 isoprenoid, as well as typical lipids of anaerobic methanotrophic archaea (ANME) like glycerol dibiphytanyl glycerol tetraether (GDGT)-0, −2, archaeol, and sn3-hydroxyarchaeol. The δ13C values of lycopane reveal linear correlations with values of PMI and squalane (n = 7; r2 = 0.71 and 0.82, respectively), probably reflecting a similar cellular function of the tail-to-tail linked isoprenoids in the archaeal source organisms. Lycopane is interpreted to represent a membrane intercalant, produced in response to extreme environmental conditions. The new observations resulting from the analysis of the Monte Palco authigenic carbonates – including the similarities in 13C-depletion of PMI, squalane, and lycopane but also with other archaeal membrane lipids like archaeol, sn3-hydroxyarchaeol, and GDGT-0 (measured as ether-cleaved biphytanes) – allowed us to re-interpret the potential source organism of lycopane in modern and ancient anoxic and euxinic basins (Cariaco Trench, Black Sea, late Cenomanian black shales of the Cape Verde Basin). These new data agree with unknown archaea as producers of lycopane as a response to environmental stress at chemoclines. The previous interpretation of lycopane as a biomarker of photoautotrophic bacteria in anoxic basins is challenged by our new findings. An alternative explanation for these occurrences is lycopane production by Marine Group II Euryarchaeota, archaea closely associated with primary producers. Lycopane production by archaea is probably more widespread than previously recognized. Future research should evaluate the potential of lycopane as a biomarker of archaeal adaptation to extreme environmental conditions.

Archaeosomes: New Generation of Liposomes Based on Archaeal Lipids for Drug Delivery and Biomedical Applications.

Archaeosomes are a new generation of stable liposomes composed of natural ether lipids extracted from archaea, or synthetic archaeal lipids. Archaea constitute a domain of single-celled microorganisms that are structurally similar to but evolutionarily distinct from bacteria. They synthesize unique membrane lipids with isoprenoid hydrocarbon side chains attached via an ether linkage to the glycerol-phosphate backbone. Compared to the ester linkages found in the lipids of Eukarya and bacteria, the ether linkages in archaeal lipids are more stable in various environmental conditions such as high/low temperatures, acidic or alkaline pH, bile salts, and enzymatic hydrolysis. This feature has intrigued scientists to use archaeal lipids to prepare archaeosomes with superior physicochemical stability and utilize them as effective carriers to deliver various cargos of biomedical importance such as drugs, proteins, peptides, genes, and antioxidants to the target site. Archaeosomes carrying antigens and/or adjuvants are also proven to be better candidates for stimulating antigen-specific, humoral, and cell-mediated immune responses, which broadens their scope in vaccine delivery. These properties associated with excellent biocompatibility and a safety profile provide numerous advantages to the archaeosomes to function as a versatile delivery system. This mini-review will provide an overview of the unique features of archaeal lipids, preparation and characterization of archaeosomes, and emphasize the prospects related to drug delivery and other biomedical applications.

Chemical composition of the lipophilic compounds from the rind and pith of papyrus (Cyperus papyrus L.) stems.

Papyrus (Cyperus papyrus L.) is a sedge plant with a high rate of biomass productivity that represents an interesting raw material to produce chemicals, materials and fuels, which are currently still obtained from fossil resources, in the context of a lignocellulosic biorefinery. In this work, the content and chemical composition of the lipids present in papyrus stems were thoroughly studied. For this, the papyrus stems were separated into the rind and the pith. The lipid content accounted for 4.1% in the rind and 4.9% in the pith (based on dry matter). The main compounds identified in both parts of the papyrus stem were hydrocarbons, n-fatty acids, 2-hydroxyfatty acids, alcohols, alkylamides, mono- and diglycerides, steroids (sterols, ketones, hydrocarbons, esters and glycosides), tocopherols, tocopherol esters, phytol, phytol esters, alkyl ferulates, ω-carboxyalkyl ferulates (and their monoglycerides), and acylglycerol glycosides. The rind presented a predominance of n-fatty acids (6790 mg/kg; that represented 28.6% of all identified compounds), steroid compounds (6255 mg/kg; 26.3%), phytol and phytol esters (4985 mg/kg; 21.0%), and isoprenoid hydrocarbons, namely phytadiene and squalene (2660 mg/kg; 11.2%), while the most abundant lipids in the pith were steroids (8600 mg/kg; 44.4% of all identified compounds) and fatty acids (6245 mg/kg; 32.2%). Due to the great diversity and significant abundance of the compounds identified in papyrus, it can be considered as a potential raw material for biorefineries to obtain valuable phytochemicals of interest to various industrial sectors.

Isoprenoid Hydrocarbons As Fingerprints For Identification Of Spill Oils In Indonesian Marine Environment

Along with the increasing transport of crude oils to the refinery sites, many accidents of oil spills have been occurred in Indonesian waters. Such spills might be purely an accident but some others are suspected to be deliberately spilled. Nevertheless, both cases need an identification system to trace back the spill source and eventually the spill data can be brought to the court as an evident. Previously, the identification system was conducted through a pattern recognition of n-paraffin hydrocarbons of crude oil samples which are very distinguished from their gas chromatographic (GC) pattern of n-C17, Pristane, n-C18, Phytane, and other nparaffin’s down to n-C30. Unfortunately, some crude oils have similar pattern that matching of two chromatograms could give an ambiguity result. Pattern recognition of isoprenoid hydrocarbons have been developed to characterized crude oils that potentially pollute the Indonesian waters. Differing from the n-paraffin that each hydrocarbon peak can be determined definitely, the developed method does not need to identify each of the isoprenoid hydrocarbons, instead pattern of their chromatographic separation are sufficiently distinguished. GC isoprenoid pattern recognition is made from the isoprenoid peaks that emerge between n-C17 and n- 18. It two crude oils having similar pattern of n-paraffin’s show very distinct pattern of iso-paraffin’s. The method thus can be used as complimentary step in matching the GC pattern of crude oil samples . Although in some cases GC isoprenoid peaks are not completely separated, this would not be disadvantages since their retention time and area can be measured and integrated definitely, respectively. Nevertheless, the separation of iso-paraffin peaks can be easily conducted using a recent GC method namely a comprehensive two dimensional gas chromatography (GCxGC), a method which is recommended to be implemented further in this research.

High-temperature pyrolysis of isoprenoid hydrocarbon p-menthane using ReaxFF molecular dynamics simulation

The pyrolysis chemistry of p-menthane, a promising “drop-in” fuel of bio-derived isoprenoid hydrocarbon, has not been well understood especially under high temperatures. In this work, the pyrolysis of p-menthane is further investigated using molecular dynamics simulations with the reactive force-field interatomic potential (ReaxFF) under 2600 K. It is found that the scission of isopropyl and the ring-open reaction in the site adjacent to the isopropyl are two predominant initiations of p-menthane decomposition in our simulations. The main generation and consumption channels of important products, such as methane and ethylene, are also tracked by the straightforward scrutinize on simulation trajectories. In addition, a detailed reaction scheme of the high-temperature pyrolysis is proposed. The apparent activation energy calculated from our reactive molecular dynamics simulations in the temperature range from 2200 K to 3000 K is 232 kJ mol−1, which is reasonably consistent with our experimental result of 225 ± 5 kJ mol−1. In summary, the simulation results provided by ReaxFF are helpful to explain pyrolysis processes readily, which is the effective verification and extension of previous experimental studies.

Use of a novel biomarker, botryococcane, to monitor biodegradation of two lacustrine‐sourced crude oils

AbstractBioremediation is a proven alternative for remediating petroleum‐impacted soils at exploration and production (E&P) sites. Monitoring remediation performance can involve detection and quantification of biodegradation resistant compounds such as C3017α(H),21β(H)‐hopane, which requires the use of gas chromatography with mass spectrometry detection (GC/MS). Due to the remoteness of many E&P sites, this technology is not always available, and alternative methods are needed to provide reliable quantitative measurements of petroleum remediation efficiency. This study provides a detailed chemical characterization of lacustrine‐sourced crude oils and a technical basis for measuring the effectiveness of bioremediation efforts for soil impacted by those crudes. We show that the novel isoprenoid hydrocarbon botryococcane is relatively stable in lacustrine‐sourced crude oils compared with C3017α(H),21β(H)‐hopane under moderate biodegradation conditions generally observed in field samples. We have also demonstrated that, due to the stability and relatively elevated concentration of botryococcane in lacustrine oils, it can be reliably measured using the more cost‐effective and available GC/FID methodology, and thereby be used to monitor the progress of ongoing soil bioremediation activities at remote sites.

Comparative Analysis of the Composition of Carbon-Rich Rocks from Domanik Deposits and the Oil–Water Contact Zone Exemplified by Tatarstan’s Bavly Oilfield

Samples of carbon-rich rocks from domanik deposits and the oil–water contact zone of the Bavly field of the Republic of Tatarstan (Russia), as well as extracts from them, have been studied by thermal analysis, IR and EPR spectroscopy, and gas–liquid chromatography. Significant differences have been revealed in the chemical composition and physicochemical properties of both soluble and insoluble organic matter from various areas of the Bavly field. Compared with bitumens from the oil–water contact zone, bitumoids from domanik deposits are heavier; they are enriched in oxidized structures and contain elevated levels of isoprenoid hydrocarbons and light normal alkanes. Bitumoid asphaltenes are enriched in sulfur and nitrogen, depleted in oxygen, and characterized by an increased concentration of paramagnetic centers. These differences have to be taken into account when testing technologies for the development of domanik deposits.

Aerosol-associated non-polar organic compounds (NPOCs) at Jammu, India, in the North-Western Himalayan Region: seasonal variations in sources and processes.

Fine particulate (PM2.5) bound non-polar organic compounds (NPOCs) and associated diagnostic parameters were studied at Jammu, an urban location in the foothills of North-Western Himalayan Region. PM2.5 was collected daily (24h, once a week) over a year to assess monthly and seasonal variations in NPOC concentration and their source(s) activity. Samples were analyzed on thermal desorption-gas chromatography mass spectrometry to identify and quantify source-specific organic markers. Homologous series of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), isoprenoid hydrocarbons and nicotine were investigated to understand the sources of aerosols in the region. The annual mean concentration of PM2.5 during the sampling period was found higher than the permissible limit of India's National Ambient Air Quality Standards (NAAQS) and World Health Organisation (WHO) guidelines. The rise of concentration for PM2.5 and associated NPOCs in summer season was attributed to enhanced emission. The n-alkane-based diagnostic parameters indicated mixed contributions of NPOCs from anthropogenic sources like fossil fuel-related combustion with significant inputs from biogenic emission. Moreover, high influence of petrogenic contributionwas observed in summer (monsoon) months. The quantifiable amounts of isoprenoid hydrocarbons further confirmed this observation. Total PAH concentration also followed an increasing trend from March to June, and June onwards a sharp decrease was observed. The higher concentration of environmental tobacco smoke marker nicotine in winter months was plausibly due to lower air temperature and conditions unfavourable to photo-degradation. A clear dominance of low molecular weight PAHs was noticed with rare presence of toxic PAHs in the ambient atmosphere of Jammu. PAH-based diagnostic parameters suggested substantial contribution from low temperature pyrolysis processes like biomass/crop-residue burning, wood and coal fire in the region. Specific wood burning markers further confirmed this observation.

Biological Degradation and Transformation Characteristics of Total Petroleum Hydrocarbons by Oil Degradation Bacteria Adsorbed on Modified Straw.

We report a simple and “green” method for the fabrication of polymer-modified straw-supported oil degradation bacteria (PMS-ODB) for biological degradation of total petroleum hydrocarbons (TPHs) in water. The modification of straw was achieved by in situ copolymerization of styrene and butyl methacrylate using methylene-bis-acrylamide as a cross-linker in an aqueous solution containing straw powders. Compared with the control group (ODB loaded on untreated straw), the results obtained from the experimental group show that the polymer-modified straw is beneficial to the growth of microorganisms. As a result, the degradation rate of TPHs reaches 90.12%, which is 50.54 and 7.08% higher than that of the blank group (ODB only) and the control group, respectively. A study on the transformation characteristics of PMS-ODB shows that the degradation rate of alkanes with low, medium, and high carbon number is higher than 90%. w(∑C21–)/w(∑C22+) (the mass ratio of normal alkanes of high carbon/low carbon), w(pr)/w(ph) (the ratio of pristane/phytane), and OEP (the mass ratio of normal alkanes of odd carbon/even carbon) for TPHs in the experimental group were measured to be 0.6186, 0.7248, and 1.4356, respectively, all of which are the largest value among the blank group, control group, and experimental group. These findings indicate that compared with the control group, the modification of straw could enhance the comprehensive biological degradation performance for TPHs, even those highly stable organics, such as carbon n-alkanes and isoprenoid hydrocarbon, which may open a new possibility for degradation of oils or toxic organics in an enhanced biological manner.

Geophysical and geochemical analysis of shallow gas and an associated pockmark field in Bantry Bay, Co. Cork, Ireland

An integrated geophysical, geological, and geochemical investigation of seabed fluid venting was carried out in upper Bantry Bay, a large marine inlet on the southwest coast of Ireland. The results provide evidence of the seafloor venting of gas rich fluids, resulting in the formation of a pockmark field identified here for the first time. The pockmarks occur in an area where sub-bottom profiles provide evidence of chimney-like features interpreted to record upward gas migration through Quaternary sediments to the seafloor. Three vibrocores up to 6 m long were acquired in water depths of 24–34 m, two from the pockmark field and one from outside. Methane of predominantly biogenic origin was quantified in all three cores by headspace analysis of sediment sub-samples. Well-defined sulfate methane transition zones (SMTZs) were observed in two of the cores, the shallowest (1.25 m below sea floor (mbsf)) inside the pockmark field and the other (3.75 mbsf) outside. It is likely that an SMTZ occurs at the location of the third core, also within the pockmark field, although deeper than the samples obtained during this study. Gas migration towards the seafloor is suggested to involve both diffuse pore fluid migration across wide areas and focused flow through the pockmarks, together driven by methanogenesis of pre-glacial lacustrine sediments preserved in a bedrock basin, and possible gas release from the Owenberg River Fault. Analysis of phospholipid fatty acids (PLFAs) and archaeal isoprenoid hydrocarbons was used to investigate the microbial ecology of these sediments. Anaerobic oxidation of methane (AOM) may play a role in controlling release of CH4 to the water column and atmosphere in this shallow gas setting, potentially mediated by syntrophic sulfate reducing bacteria (SRB) and anaerobic methanotrophic archaea (ANME).

Source apportionment and health risk assessment of organic constituents in fine ambient aerosols (PM2.5): A complete year study over National Capital Region of India

Fine ambient aerosols (PM2.5) levels in the atmosphere are continuously worsening over Delhi and National Capital Region (NCR) of India. Complete source profiles are required to be assessed for implementation of proper mitigation measures over the NCR. In this study, emission sources of PM2.5 are reported for the NCR of India for samples collected during December 2016 to December 2017 at three sampling sites in Delhi, Uttar Pradesh and Haryana. Organic constituents (n-alkanes, isoprenoid hydrocarbons, polycyclic aromatic hydrocarbons, phthalates, levoglucosan and n-alkanoic acids) in PM2.5 were measured to apportion the sources over the study area. Source apportionment of PM2.5 was performed using organic constituents by Positive Matrix Factorization (PMF) and Principal Component Analysis (PCA). Health risk associated with organic pollutants [PAHs and carcinogen BEHP bis(2-ethylhexyl) phthalate] demonstrated the threat of PM2.5 exposure via inhalation. Transport pathways of air masses were evaluated using 3-day backward trajectories and observed that some air masses originated from local sources along with long-range transport which influenced the PAHs concentration during most of the study period over the NCR. PMF and PCA resulted in the five major emission sources [vehicular emissions (32.2%), biomass burning (30%), cooking emissions (16.8%), plastic burning (13.4%), mixed sources (7.6%) including biogenic and industrial emissions] for PM2.5 over the sampling sites. The present study reveals that transport sector is a major source to be targeted to reduce the vehicular emissions and consequent health risks associated with organic pollutants especially PAHs.

High-pressure pyrolysis of isoprenoid hydrocarbon p-menthane in a tandem micro-reactor with online GC–MS/FID

Isoprenoids have been synthesized in large quantities through metabolic engineering method using some microorganisms as hosts and biomass as carbon resources. An isoprenoid cyclic hydrocarbon, p-menthane, is considered as a promising “drop-in” fuel to substitute traditional cycloalkane components, however, its pyrolysis data is lacking so far which is a significant part of the fuel combustion chemistry, especially under high pressures. In this work, pyrolysis experiments of p-menthane were carried out in a tandem micro-reactor under temperature of 450–800 °C and pressure of 2 MPa. 39 species were identified and quantified by online GC–MS/FID, based on which some initial pyrolysis pathways were determined. The early production of 4-methyl-1-cyclohexene and 1-isopropyl-1-cyclohexene indicates that methyl and isopropyl scission happen at the initial stage followed by H-transfer reaction and dehydrogenation. The activation energy Ea and pre-exponential factor A of the overall reaction were calculated as 225 kJ mol−1 and 1.17 × 1012 s−1, respectively. For secondary reactions, many conjugated dienes such as 1,3-butadiene and 2-methyl-1,3-butadiene and small olefins such as ethylene and propene are generated through the ring-opening pathways. Benzene and toluene are the most abundant products among aromatics detected which are formed through dehydrogenation and demethylation of some early species like 4-methyl-1-cyclohexene and side-chain scission of aromatics. A particular product 1,3-hexadien-5-yne was detected which is generated through ring-opening pathways followed by H-transfer and demethylation reactions and could isomerized to benzene. A lumped kinetic model was proposed to describe the pyrolysis of p-menthane which exhibited good agreement with the experimental data.

COMPOSITIONS OF HYDROCARBONS AND HETEROORGANIC COMPOUNDS IN ORGANIC SUBSTANCE AND PRODUCTS OF THERMAL DECOMPOSITION UNDER SUPERCRITICAL CONDITIONS OF KEROGEN IN OIL SHALE FROM CHIM-LOPTYUG DEPOSIT

New data are presented on the chemical nature of the organic substance in the sample of oil shale from the Upper Jurassic deposits, the section of the Chim-Loptyug area of the Yarengsky shale-bearing territory in the Timan-Severouralsk region (the Komi Republic) and in the products of its thermal dissolution in the supercritical flow of the aromatic solvent (benzene). The soluble organic substance in the sample under study was shown to be highly resinous and sour. Thermolysis of shale material in benzene under supercritical conditions increased the yield of the liquid product due to the destruction of bridge (C-S) and C-C bonds in kerogen. The contents of sulfur and oil components were found to increase in the composition of the resulting pyrolyzate. According to the chromatographic-mass spectrometric analysis bitumoid and pyrolyzate oils contained normal and isoprenoid alkanes, polycycloalkanes, mono- and polycyclic aromatic hydrocarbons and heteroorganic compounds. The pyrolyzate oils are characterized by the presence of unsaturated compounds in the hydrocarbon composition and a wider set of sulfur- and oxygen-containing structures. The sets of hydrocarbon and hetero-organic compounds identified in the pyrolyzate oils are typical for oily components in oils, which enables to consider pyrolizate as a raw material for the production of a wide range of fuels and lubricants, as well as valuable products for national economy. Based on the data on the distribution of biomarker hydrocarbons and the values of the calculated geochemical coefficients of the accumulation of organic substance in the investigated sample of oil shale it was established to occur in a sharply reducing situation in argillaceous deposit with a high contribution of marine phytoplankton to the initial biomass. The low thermal maturity of the organic substance indicates its high generation potential.Forcitation:Kovalenko E.Yu., Sagachenko T.A., Min R.S., Patrakov Yu.F. Compositions of hydrocarbons and heteroorganic compounds in organic substance and products of thermal decomposition under supercritical conditions of kerogen in oil shale from Chim-Loptyug deposit. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 7. P. 98-104

The radiation-induced fragmentation of high-molecular-weight isoprenoid hydrocarbons present in high-boiling petroleum fractions

The radiation-induced fragmentation of squalane, phytane and high-molecular-weight isoprenoid hydrocarbons present in high-boiling petroleum fractions was investigated. The structure of the isoprenoids was determined by 13C NMR spectroscopy, and the identification and quantification of their radiolysis products was performed by gas chromatography. It was found that the vast majority of high-molecular-weight isopranes present in the samples have a regular (i.e., head-to-tail) structure and that their terminal groups have methyl branches at positions 2,6,10,…; 3,7,11,…; 4,8,12,…and 6,10,14,…The ratio of radiation-chemical yields of fragment isoprenoids to that of n-alkanes (G(isop)/G(n-alkane)) correlates well with the isoprenoid content in the sample. Based on the concentration distribution of radiolytic products, an attempt was made to reconstruct the quantitative ratio of isoprenoid end groups in the samples.

Biosynthetic machinery for C25,C25-diether archaeal lipids from the hyperthermophilic archaeon Aeropyrum pernix

Archaea that thrive in harsh environments usually produce membrane lipids with specific structures such as bipolar tetraether lipids. Only a few genera of archaea, which are hyperthermophiles or halophiles, are known to utilize diether lipids with extended, C25 isoprenoid hydrocarbon chains. In the present study, we identify two prenyltransferases and a prenyl reductase responsible for the biosynthesis of C25,C25-diether lipids in the hyperthermophilic archaeon Aeropyrum pernix. These enzymes are more specific to C25 isoprenoid chains than to C20 chains, which are used for the biosynthesis of ordinary C20,C20-diether archaeal lipids. The recombinant expression of these enzymes with two known archaeal enzymes allows the production of C25,C25-diether archaeal lipids in the cells of Escherichia coli.

Tricyclic terpane geochemistry of source rocks from Northwestern and Central Niger Delta

ABSTRACTThis distribution of tricyclic terpanes in source rocks from the northwestern and central Niger Delta was used to evaluate their origin, depositional environment and thermal maturity. The rock samples were extracted using Soxhlet extraction method and the saturated hydrocarbon fraction was analysed for biomarkers using gas chromatography-mass spectrometry (GC-MS). The values of soluble organic matter (SOM) and total hydrocarbons for wells AW and OP source rock samples exceeded the minimum 500 ppm and 300 ppm, respectively with values indicating very good to excellent potential source rocks. The tricyclic terpane source parameters and the complementary distribution of hopanes, regular C27-C29 steranes, n-alkanes and acyclic isoprenoid hydrocarbons showed that samples from well AW consist of mixed marine/terrestrial organic matter while those from well OP consist of organic matter largely from terrestrial origin. The values of Pr/Ph ratio for source rock samples from wells AW and OP indicate deposition of the organic matter under suboxic conditions. Sterane and hopane biomarker maturity parameters indicated that the source rock samples from wells AW and OP are at onset of oil generation and main oil window, Most of the source rock samples from well AW are more thermally mature than those from well OP. The results of tricyclic terpane maturity parameters indicated low thermal maturity for the rock samples from both wells with samples from well AW more thermally mature than those from well OP.

An exception among diatoms: unique organization of genes involved in isoprenoid biosynthesis in Rhizosolenia setigera CCMP 1694.

The marine diatom Rhizosolenia setigera is unique among this group of microalgae given that it is only one of a handful of diatom species that can produce highly branched isoprenoid (HBI) hydrocarbons. In our efforts to determine distinguishing molecular characteristics in R. setigera CCMP 1694 that could help elucidate the underlying mechanisms for its ability to biosynthesize HBIs, we discovered the occurrence of independent genes encoding for two isopentenyl diphosphate isomerases (RsIDI1 and RsIDI2) and one squalene synthase (RsSQS), enzymes that catalyze non-consecutive steps in isoprenoid biosynthesis. These genes are peculiarly fused in all other genome-sequenced diatoms to date, making their organization in R. setigera CCMP 1694 a clear distinguishing molecular feature. Phylogenetic and sequence analysis of RsIDI1, RsIDI2, and RsSQS revealed that such an arrangement of individually transcribed genes involved in isoprenoid biosynthesis could have arisen through a secondary gene fission event. We further demonstrate that inhibition of squalene synthase (SQS) shifts the flux of exogenous isoprenoid precursors towards HBI biosynthesis suggesting the competition for isoprenoid substrates in the form of farnesyl diphosphate between the sterol and HBI biosynthetic pathways in this diatom.

Isolation and Characterization of Cyclic C33 Botryococcenes and a Trimethylsqualene Isomer from Botryococcus braunii Race B.

Three cyclic C33 botryococcenes and one new trimethylsqualene isomer were isolated from the B race, Showa (Berkeley) strain of Botryococcus braunii, which is known to produce large amounts of isoprenoid hydrocarbons ranging in carbon number from 30 to 34. Their purity was determined by GC-MS, and structures were characterized by 1D and 2D NMR. One of these molecules, cyclic C33-1 botryococcene (5), has an unusual connection of a methylenecyclohexane ring to the molecule backbone not seen before in botryococcenes. This report further adds to our knowledge of the wide range of isoprenoid hydrocarbon structures produced by B.braunii.

Biodegradation of crude oil and phenanthrene by heavy metal resistant Bacillus subtilis isolated from a multi-polluted industrial wastewater creek

A critical bottleneck associated with bioremediation technology in multi-polluted environments is microbiostasis due to metal toxicity. Autochthonous Bacillus species that would harness a repertory of traits to catabolize hydrocarbons and simultaneously sequester heavy metals (HMs) is invaluable in the environment contaminated with divergent pollutants. Fourteen HM-resistant bacilli from polluted creek were characterized using phenotypic and molecular criteria, and studied for hydrocarbon degradation in chemically defined media amended with Co2+ and Ni2+ (5.0 mmol l−1 each). Phylogenetic analyses revealed distribution of the bacilli into three clades. Two dissimilar strains of Bacillus subtilis (M16K, and M19F) with 19.1% sequence divergence, exhibited excellent degradation of crude oil (>94.0%) with evidence of early degradation of isoprenoid hydrocarbons and concurrent metal removal 18 d post-inoculation. Similarly, phenanthrene degradation (>85.0%), and corresponding metal detoxification occurred in 28 d axenic culture of the strains. Strain M16K and M19F were metabolically active in matrices containing HMs, degraded hydrocarbons and simultaneously removed HMs from the medium. To the best of our knowledge, this is the first report of metal-resistant Bacillus subtilis strains showing simultaneous degradation of hydrocarbons and detoxification of metals, particularly in the Sub-Saharan Africa. The bacilli could be useful as potential biological agents in effective bioremediation campaign for multi-polluted environments.

Biogeochemistry of intertidal microbial mats from Qatar: New insights from organic matter characterisation

Understanding early organic matter (OM) alteration and preservation in marine carbonate-evaporite systems could improve understanding of carbon cycling and hydrocarbon source rock prediction in such environments. It is possible that organic-rich microbial mats are important contributors to preserved hydrocarbons and, to explore this, we examined changes in lipid composition in such a mat from a mesohaline intertidal lagoon, eastern Qatar. The mat reaches>5cm thickness over a carbonate mud substrate, rich in seagrass, gastropods and other small bioclasts. Clear lamination, with distinct downward colour changes from green to pink to brown, reflects different microbial mat communities. The layers contain spheroids of probable dolomite, the precipitation of which was plausibly bacterially-mediated. Lipids [n-alkanes, fatty acids (FAs), hopanoids, isoprenoid hydrocarbons, dialkyl glycerol diethers (DAGEs), and isoprenoid (0–4) and branched (Ia–IIIa) GDGTs] reflected the diverse mat-building phototrophic, heterotrophic and chemoorganotrophic microorganisms, as well as some likely allochthonous material (i.e. steroids, n-alkanols, high molecular weight n-alkanes). The lipids clearly documented the change in microbial community, with phytene(s) being the predominant hydrocarbon in the phototrophic surface layer. O2 and pH dropped significantly 0.2cm below the mat surface, coincident with the predominance of Deltaproteobacteria and increased concentrations of archaeal and bacterial glycerol dialkyl glycerol tetraether lipids and C15/C16 and C16/C17 dialkyl glycerol ether lipids in the deeper layers. Archaeol, likely of methanogen origin, was most abundant in the deepest layer. Allochthonous inputs occurred throughout the mat, including abundant steroids, especially dinosterol and dinostanol, possibly related to periodic algal (dinoflagellate) blooms in the Arabian Gulf. Both n-alkanes and n-alkanols appeared to be derived from seagrass. OM content decreased in the deepest mat; this suggests an overall low preservation potential of OM in intertidal mesohaline-hypersaline mats of the Arabian Gulf, which in turn suggests that these are not the major source of hydrocarbons in microbially-dominated carbonate-evaporite systems.