Jordi F. López

A NEW FOSSIL RESIN WITH BIOLOGICAL INCLUSIONS IN LOWER CRETACEOUS DEPOSITS FROM ÁLAVA (NORTHERN SPAIN, BASQUE-CANTABRIAN BASIN)

Abstract The occurrence of amber in Sierra de Cantabria (Álava, Basque Country) has been known for more than two decades but biological inclusions have only recently been found. The existence of crustaceans (amphipods and isopods), chelicerates (acari and arachnids), 12 orders of insects, and several bird feathers are reported in this preliminary study. In addition, there are leaf remains, molluscs, and a fair number of inorganic inclusions. Pollen analysis of the clastic series indicates an age between upper Aptian—middle Albian, which allows an assignment of this stratigraphic unit to the Nograro Formation. Chemical analysis indicates that the amber has high maturity, which reflects its Cretaceous age. Chemical composition analysis also indicates an araucariacean origin, which is corroborated by pollen found within the amber deposit. This new fossil site provides information for the reconstruction of paleocommunities of arthropods and sedimentary environments in the extreme south of the Basque-Cantabrian Basin during the Lower Cretaceous, characterized by coniferous forests with an understory of vascular cryptograms. Some of the identified arthropods add to the fossil record for various groups that are poorly known or unknown for this time period. This Lagerstätte constitutes one of the most important deposits of Mesozoic amber in the world.

Ergosterol biosynthesis pathway in Aspergillus fumigatus

The sterol composition of Aspergillus fumigatus for the biosynthesis of ergosterol is of interest since this pathway is the target for many antifungal drugs in clinical use. The sterol composition of this fungal species was analyzed by gas chromatography-mass spectrometry in different strains (susceptible and resistant to azole drugs). Also, sterols were analyzed in several A. fumigatus mutant strains deficient in enzymatic steps of the ergosterol biosynthesis pathway such as 14-alpha sterol demethylases (Cyp51A and Cyp51B) and C-5 sterol desaturases (Erg3A, Erg3B and Erg3C). All sterols identified from azole-resistant A. fumigatus strains were qualitatively and quantitatively similar to the susceptible strain (CM-237). However, sterol composition of mutants strains were different depending on the lacking enzyme. The analysis of the sterol composition in these mutant strains led to a better understanding of the ergosterol biosynthesis pathway in this important fungus.

Sulfur-binding in recent environments: II. Speciation of sulfur and iron and implications for the occurrence of organo-sulfur compounds

Speciation of iron and sulfur species was determined for two recent sediments (La Trinitat and Lake Ciso) which were deposited in environments with a high biological productivity and sulfate-reducing activity. In sediments from calcite ponds of La Trinitat an excess of reactive iron species (iron monosulfides, iron hydroxides) results in a depletion of reactive sulfur which is accompanied by a virtual absence of organo-sulfur compounds, both in low (LMW) and high molecular-weight (HMW) fractions. Small amounts of phytanyl and highly branched isoprenoid (HBI) thiophenes in the extract demonstrate that these molecules exhibit a higher reactivity towards reduced sulfur species as compared to detrital iron. Euxinic sediments from Lake Ciso are characterised by an excess of reduced sulfur species which can rapidly trap reactive iron. High concentrations of H2S results in the formation of organo-sulfur compounds which were encountered in both LMW and HMW fractions. The major part of the organic sulfur is bound to the carbohydrate portion of woody tissues, whose presence was revealed by a specific alkylthiophene distribution in the flash pyrolysate and by Li/EtNH2 desulfurisation of the kerogen which resulted in the solubilisation of the sulfur-enriched hemicellulose fraction. Relatively high amounts of sulfurised C25 HBI compounds in the sediment extract of Lake Ciso reflect the incorporation of sulfur into algal derived organic matter upon early diagenesis. The combined approach of the speciation of iron and sulfur species and the molecular analysis of sedimentary fractions demonstrates that abiotic sulfur binding to organic matter occurs at the earliest stages of diagenesis under specific depositional conditions (anoxic, stratified water column) in which an excess of reduced sulfur species relative to the amount of reactive iron is a controlling factor.

Mevalonate governs interdependency of ergosterol and siderophore biosyntheses in the fungal pathogen Aspergillus fumigatus

Aspergillus fumigatus is the most common airborne fungal pathogen for humans. In this mold, iron starvation induces production of the siderophore triacetylfusarinine C (TAFC). Here we demonstrate a link between TAFC and ergosterol biosynthetic pathways, which are both critical for virulence and treatment of fungal infections. Consistent with mevalonate being a limiting prerequisite for TAFC biosynthesis, we observed increased expression of 3-hydroxy-3-methyl-glutaryl (HMG)-CoA reductase (Hmg1) under iron starvation, reduced TAFC biosynthesis following lovastatin-mediated Hmg1 inhibition, and increased TAFC biosynthesis following Hmg1 overexpression. We identified enzymes, the acyl-CoA ligase SidI and the enoyl-CoA hydratase SidH, linking biosynthesis of mevalonate and TAFC, deficiency of which under iron starvation impaired TAFC biosynthesis, growth, oxidative stress resistance, and murine virulence. Moreover, inactivation of these enzymes alleviated TAFC-derived biosynthetic demand for mevalonate, as evidenced by increased resistance to lovastatin. Concordant with bilateral demand for mevalonate, iron starvation decreased the ergosterol content and composition, a phenotype that is mitigated in TAFC-lacking mutants.

A molecular isotopic study of 13C-enriched organic matter in evaporitic deposits : recognition of CO2-limited ecosystems

Abstract Biomarkers were analysed in a surface sediment from La Trinitat saltern ponds and a Miocene marl from the Northern Appenines. Both are characterised by enriched δ 13 C values for bulk organic matter and for biomarkers, i.e. heavier than −20‰. Exceptions are long-chain C 22 –C 34 n -alkanes and C 16 –C 20 fatty acids which have values typically lighter than −20‰, suggesting that they are not derived from aquatic organisms but from surrounding terrestrial vegetation. The enriched δ 13 C values for biomarkers of different algae and bacteria suggest that the local (microbial mat) ecosystem may have been CO 2 -limited.

Transformation of PBDE mixtures during sediment transport and resuspension in marine environments (Gulf of Lion, NW Mediterranean Sea)

Polybromodiphenyl ethers (PBDEs) in superficial sediments from the Gulf of Lion were studied. They were largely predominated by BDE 209 (98.7% of all PBDEs) indicating that the main source of these pollutants was the commercial mixture deca-BDE. This compound and the less brominated BDE exhibited a southwestward decreasing concentration gradient following the dominant marine currents and bottom relief, e.g. the Mud Belt, the submarine canyons and the Open Continental Slope. All PBDEs exhibited statistically significant correlations confirming the common origin. However, a progressive transformation of the dumped BDE 209 was identified showing a depletion paralleled by increases of the less brominated BDEs (from 8.6% to 22%). These less brominated compounds were accumulated at about 100-140 km away from the Rhone prodelta, e.g., at the end of the submarine canyons, evidencing that these transformation compounds can be accumulated at long distances from the dumping sites in the marine system.

Aspergillus fumigatus C-5 Sterol Desaturases Erg3A and Erg3B: Role in Sterol Biosynthesis and Antifungal Drug Susceptibility

ABSTRACT Two erg3 genes encoding C-5 sterol desaturase enzymes (Erg3A and Erg3B) in Aspergillus fumigatus were characterized with respect to their nucleotide sequences and null mutant phenotypes. Targeted disruption of the erg3A and erg3B genes and a double gene knockout, erg3A−erg3B−, showed that they are not essential for A. fumigatus viability. Mutant phenotypes clearly showed that Erg3B is a C-5 sterol desaturase, but no apparent role for Erg3A in A. fumigatus ergosterol biosynthesis was found. Susceptibility to amphotericin B, itraconazole, fluconazole, voriconazole, and ketoconazole was not altered in isolates in which erg3A and erg3B were knocked out alone and in combination.

Sulphur-binding in recent environments. I. Lipid by-products from Ni2B desulphurization

Selected geochemically relevant model compounds were subjected to the nickel boride desulphurization method. Poor hydrogenating properties of this agent were observed in the case of sterically hindered double bonds. Apart from its desulphurizing properties, a significant number of functionalities present in lipid compounds were transformed on treatment with nickel boride. Ketones were reduced to their alcohols whereas aldehydes were partly converted to their ketals. Although alcohols and esters were unaffected by this agent, a nearby unsaturation (i.e., position α) resulted in the loss of the alcohol group and cleavage of the ester bond, respectively. The significance of these results was demonstrated by desulphurization experiments on polar fractions from two recent sediment extracts. The main compound among the apolar products obtained, phytane, was found to be quantitatively derived from phytol and not, as may be presumed, from its macromolecularly sulphur-bound precursor. The results of this work show that compounds generated by nickel boride desulphurization of polar fractions from lipid extracts, particularly from recent sediments, are not necessarily derived from their sulphur-bound precursors. Conclusions with regard to the palaeoenvironmental significance of the hydrocarbons formed, therefore, should be made with caution.

Sterols of melanized fungi from hypersaline environments

The lipid compositions of melanized fungi isolated from calcite, gypsum and halite depositional environments of Mediterranean solar salterns, namely Hortaea werneckii, Alternaria alternata, Cladosporium cladosporioides, Cladosporium sp. and Aureobasidium pullulans, have been examined. Sterols constituted the most distinct lipid fraction. Ergosterol, 24-methylcholesta-5,7,22-trien-3b-ol, dominated all distributions but major diAerences between species were encountered when considering the subordinate sterols. Thus, 24-methylcholest-7-en-3b-ol, 24-methylcholesta7,24(28)-dien-3b-ol and 4a,24-dimethylcholest-7-en-3b-ol were found in significant proportions in Cladosporium spp (14‐20%), A. alternata (28%) and H. wernekii (29%), respectively. These sterols can be used for discrimination between these diAerent fungal species. 24-Methylcholest-7-en-3b-ol and 24-methylcholesta-7,24(28)-dien-3b-ol were found in significant proportion in the water column particles and sediments of the gypsum and halite precipitation ponds (the latter only in the halite domain). In such environments, these sterols may provide a specific signature for these melanized fungi. However, water column particulate matter and sediments from hypersaline depositional settings show sterol compositions dominated by the constituents typically encountered in phytoplankton and zooplankton, but not in melanized fungi. # 2000 Elsevier Science Ltd. All rights reserved.

13C-contents of sedimentary bacterial lipids in a shallow sulfidic monomictic lake (Lake Cisó, Spain)

Abstract Stable carbon isotopic analysis was performed on sedimentary biomarkers of a shallow sulfide-rich monomictic lake, Lake Ciso (NE Spain). Specific biomarkers derived from phototrophic sulfur bacteria in Lake Ciso were considerably depleted in 13C, most likely due to the depleted 13C-content of the dissolved inorganic carbon that was photosynthetically fixed. Recycling of respired CO2, a well-known phenomenon in monomictic lakes, probably caused this depletion. The stable carbon isotopic composition of terrestrial markers, such as C25–33 odd-carbon-numbered n-alkanes and C22–30 even-carbon-numbered n-alkan-1-ols and fatty acids, were rather similar to each other and their 13C depleted values (c. −31 to −35‰) indicated that they were derived from the surrounding vegetation. Phytol was predominantly derived from the bacteriochlorophylls of phototrophic purple sulfur bacteria as were specific fatty acids.