Purple sulfur bacteria (PSB) are important photoautotrophs inhabiting chemoclines in euxinic and meromictic lakes. These organisms are the only producers of the carotenoid, okenone, a compound that has been targeted as a biomarker for photic zone euxinia, particularly in ancient sedimentary environments. Although the natural occurrence and geochemistry of this compound has been studied previously, this is the first systematic and comprehensive report on the microbial physiology of okenone production in pure cultures. Four strains/species: Marichromatium purpuratum DSMZ 1591, Marichromatium purpuratum DSMZ 1711, Thiocapsa marina DSMZ 5653, and FGL21 (isolated from Fayetteville Green Lake, New York) were chosen because they produce okenone and Bacteriochlorophyll a (Bchl a). We developed a new, in vivo technique for the quantification of okenone allowing for more rapid and accurate quantification. The ratio of okenone to Bchl a differs among species and strains of PSB, varying from 0.463 +/- 0.002 to 0.864 +/- 0.002. Photoheterotrophically grown PSB have statistically significant, lowered okenone:Bchl a ratios, decreasing from 0.784 +/- 0.009 under autotrophic metabolism to 0.681 +/- 0.002, which we interpret to indicate a decreased requirement for okenone when PSB are provided with a complex (> C1) carbon source. The variation in okenone production raises the question on whether okenone expression is constitutive or inducible. The broader implication is that concentrations of okenone in sediments are dependent on metabolism and species composition, and not solely on PSB cell density.

The mechanism leading to the formation of aliphatic components in sedimentary rocks and petroleum products has been the subject of debate. Recent research has concluded that algaenan is not as widespread ecologically or phylogenetically, so may contribute less to the resistant aliphatic content of kerogens where such algae are source organisms. We conducted experiments with the non-algaenan producing alga, Chlamydomonas reinhardtii, at 260 and 350 degrees C and 700 bar to simulate fossilization of the microorganism under confined pyrolysis conditions. Pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) analysis revealed that the unheated alga consisted of biopolymers primarily related to proteins and lipids, including C-16 and C-18 fatty acids (FAs). However, heating at 260 and 350 degrees C resulted in macromolecules with a significant aliphatic component similar to high hydrogen content kerogen, derived from lipids in the alga, primarily from saturated and unsaturated C-16 and C-18 FAs, as determined from experiments with model compounds. The presence of amides, nitriles and oximes in the heated alga was likely due to the reaction of the lipids with the abundant N-containing proteinaceous compounds. Py-GC-MS of the residue of Scenedesmus quadricauda at 350 degrees C (a green alga containing algaenan as a control) demonstrated survival of algaenan at that temperature. The solvent insoluble residue of a cyanobacterium (Oscillatoria sp.) and a purple non S containing bacterium Rhodopseudomonas palustris subjected to similar high temperature and pressure, resulted in a residue with significant aliphatic content. The results reveal that algaenan survived the P/T conditions of the experiments, which additionally suggest an alternative mechanism that may lead to aliphatic geopolymers. Since this mechanism seems to be valid for organisms that are phylogenetically wide apart, it may be valid for organism cells in general. Thus, bacterial biomass may also contribute to the insoluble organic inventory of ancient sediments. (C) 2013 Elsevier Ltd. All rights reserved.

Organic nanoglobules are microscopic spherical carbon-rich objects present in chondritic meteorites and other astromaterials. We performed a survey of the morphology, organic functional chemistry, and isotopic composition of 184 nanoglobules in insoluble organic matter (IOM) residues from seven primitive carbonaceous chondrites. Hollow and solid nanoglobules occur in each IOM residue, as well as globules with unusual shapes and structures. Most nanoglobules have an organic functional chemistry similar to, but slightly more carboxyl-rich than, the surrounding IOM, while a subset of nanoglobules have a distinct, highly aromatic functionality. The range of nanoglobule N isotopic compositions was similar to that of nonglobular 15N-rich hotspots in each IOM residue, but nanoglobules account for only about one third of the total 15N-rich hotspots in each sample. Furthermore, many nanoglobules in each residue contained no 15N enrichment above that of bulk IOM. No morphological indicators were found to robustly distinguish the highly aromatic nanoglobules from those that have a more IOM-like functional chemistry, or to distinguish 15N-rich nanoglobules from those that are isotopically normal. The relative abundance of aromatic nanoglobules was lower, and nanoglobule diameters were greater, in more altered meteorites, suggesting the creation/modification of IOM-like nanoglobules during parent-body processing. However, 15N-rich nanoglobules, including many with highly aromatic functional chemistry, likely reflect preaccretionary isotopic fractionation in cold molecular cloud or protostellar environments. These data indicate that no single formation mechanism can explain all of the observed characteristics of nanoglobules, and their properties are likely a result of multiple processes occurring in a variety of environments.

The interaction of hydrogen and deuterium with dimethylamine borane (Me2NHBH3) was studied at pressures from 0 to 10 GPa. Me2NHBH3 is stable to isothermal compression in noble gas pressure media up to 16 GPa. During these compressions a strong positive pressure dependence of the frequencies of BN and BH stretching fundamentals was observed. The opposite trend was observed with NH modes. Me2NHBH3 + He mixtures remain phase separated over the entire 0-16 GPa range. During the isothermal compression of Me2NHBH3 + H-2 mixtures two separate phases are observed at low pressure which subsequently collapse into one phase above 3 GPa. Prior to the formation of the Me2NHBH3/H-2 phase loss of the H-2 vibron was observed concurrently with the growth of broad features in the 3600-4000 region. Further compression of the Me2NHBH3:H-2 results in the growth of new Raman-active BN, BH, and NH modes not present in noble gas compressions. These modes are assigned to the new high pressure solid: [(Me2NH)(2)BH2+][BH4-] similar called diammoniate of diborane often observed in experiments with ammonia and diborane at ambient pressure.

The novel hydrogen-rich BN materials Me2NHBH3 and c-N2B2H4Me4 have been studied by a combination of vibrational spectroscopy and single crystal X-ray diffraction over the pressure range 0-40 GPa. Assignments of Raman-active vibrational modes were made for c-N2B2H4Me4 on the basis of a combination of gas-phase predictions and previous assignments for similar compounds. The Raman spectrum of single crystals were found to have excellent signal-to-noise for pressures over the 0-40 GPa range, making it an ideal method for in situ analysis of high pressure reactions involving c-N2B2H4Me4. The enthalpy of the reaction c-N2B2H4Me4 + 2 H-2 -> 2 Me2NHBH3 was estimated to be 2.9 kcal/mol endothermic at ambient pressure. The corresponding pressure dependence of Delta G(rxn), was estimated from the P-V equations of state (EOS) measured for Me2NHBH3, c-N2B2H4Me4, and H-2 over the 0-12 GPa range. Using the EOS for fluid hydrogen, the reaction is estimated to have a favorable Delta Delta G(rxn) of 10 kcal/mol over the 0-2 GPa pressure range. Above 2 GPa, a positive pressure dependence of Delta G(rxn) is observed. On the basis of these experimental observations, we estimate the reaction thermochemistry to approach a thermoneutral equilibrium over the 0-2 GPa range. Above 2 GPa, the reaction volume becomes positive, causing this hydrogenation pathway to remain unfavorable over a pressure range extending to greater than 100 GPa at 298 K.

Here, we present the results of a multitechnique study of the bulk properties of insoluble organic material (IOM) from the Tagish Lake meteorite, including four lithologies that have undergone different degrees of aqueous alteration. The IOM C contents of all four lithologies are very uniform and comprise about half the bulk C and N contents of the lithologies. However, the bulk IOM elemental and isotopic compositions vary significantly. In particular, there is a correlated decrease in bulk IOM H/C ratios and delta D values with increasing degree of alteration-the IOM in the least altered lithology is intermediate between CM and CR IOM, while that in the more altered lithologies resembles the very aromatic IOM in mildly metamorphosed CV and CO chondrites, and heated CMs. Nuclear magnetic resonance (NMR) spectroscopy, C X-ray absorption near-edge (XANES), and Fourier transform infrared (FTIR) spectroscopy confirm and quantitate this transformation from CR-like, relatively aliphatic IOM functional group chemistry to a highly aromatic one. The transformation is almost certainly thermally driven, and probably occurred under hydrothermal conditions. The lack of a paramagnetic shift in C-13 NMR spectra and 1s-sigma* exciton in the C-XANES spectra, both typically seen in metamorphosed chondrites, shows that the temperatures were lower and/or the timescales were shorter than experienced by even the least metamorphosed type 3 chondrites. Two endmember models were considered to quantitatively account for the changes in IOM functional group chemistry, but the one in which the transformations involved quantitative conversion of aliphatic material to aromatic material was the more successful. It seems likely that similar processes were involved in producing the diversity of IOM compositions and functional group chemistries among CR, CM, and CI chondrites. If correct, CRs experienced the lowest temperatures, while CM and CI chondrites experienced similar more elevated temperatures. This ordering is inconsistent with alteration temperatures based on mineralogy and O isotopes.

The Sutter's Mill (SM) meteorite fell in El Dorado County, California, on April 22, 2012. This meteorite is a regolith breccia composed of CM chondrite material and at least one xenolithic phase: oldhamite. The meteorite studied here, SM2 (subsample 5), was one of three meteorites collected before it rained extensively on the debris site, thus preserving the original asteroid regolith mineralogy. Two relatively large (10 mu m sized) possible diamond grains were observed in SM2-5 surrounded by fine-grained matrix. In the present work, we analyzed a focused ion beam (FIB) milled thin section that transected a region containing these two potential diamond grains as well as the surrounding fine-grained matrix employing carbon and nitrogen X-ray absorption near-edge structure (C-XANES and N-XANES) spectroscopy using a scanning transmission X-ray microscope (STXM) (Beamline 5.3.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory). The STXM analysis revealed that the matrix of SM2-5 contains C-rich grains, possibly organic nanoglobules. A single carbonate grain was also detected. The C-XANES spectrum of the matrix is similar to that of insoluble organic matter (IOM) found in other CM chondrites. However, no significant nitrogen-bearing functional groups were observed with N-XANES. One of the possible diamond grains contains a Ca-bearing inclusion that is not carbonate. C-XANES features of the diamond-edges suggest that the diamond might have formed by the CVD process, or in a high-temperature and -pressure environment in the interior of a much larger parent body.

The genus Ecphora of Muricid gastropods from the mid-Miocene Calvert Cliffs, Maryland is characterised by distinct reddish-brown colouration that results from shell-binding proteins associated with pigments within the outer calcite (CaCO3) portion of the shell. The mineral composition and robustness of the shell structure make Ecphora unique among the Neogene gastropods. Acid-dissolved shells produce a polymeric sheet-like organic residue of the same colour as the initial shell. NMR analysis indicates the presence of peptide bonds, while hydrolysis of the polymeric material yields 11 different amino acid residues, including aspartate and glutamate, which are typical of shell-binding proteins. Carbon and nitrogen elemental and isotopic analyses of the organic residue reveals that total organic carbon ranges from 4 to 40 weight %, with 11 < C/Nat < 18. Isotope values for carbon (-17 < delta C < - 15%) are consistent with a shallow marine environment, while values for nitrogen (4 < delta N < 12.2%) point to Ecphora's position in the trophic structure with higher values indicating predator status. The preservation of the pigmentation and shell-binding proteinaceous material presents a unique opportunity to study the ecology of this important and iconic Chesapeake Bay organism from 8 to 18 million years ago.