Martín-Cabello, G., Terrón-González, L., Ferrer, M., Santero, E., 2020. Identification of a complete dibenzothiophene biodesulfurization operon and its regulator by functional metagenomics. Environmental Microbiology 22, 91-106.

https://doi.org/10.1111/1462-2920.14823 Functional screening for aromatic ring oxygenases of an oil contaminated soil metagenome identified 25 different clones bearing monooxygenases coding genes. One fosmid bore an operon containing four tightly linked genes coding for a complete dibenzothiophene biodesulfurization pathway, which included the predicted monooxygenases DszC and DszA, the desulfinase DszB, and an FMN-oxidoreductase designated DszE. The dszEABC Escherichia coli operon provided with the ability to use dibenzothiophene as the only sulfur source. N Transcription of the operon is driven from a σ -dependent promoter and regulated by an activator that was N dszR in vitro designated . DszR has been purified and characterized and shown to be a constitutively active σ - dependent activator of the group IV, which binds to two contiguous sequences located upstream of the dsz dszE dszR promoter. The promoter and and genes have apparently been recruited from an aliphatic sulfonate N biodegradation pathway. If transcribed from a heterologous upstream promo ter, the σ -dependent promoter dszE region functions as an 'insulator' that prevents translation of , by binding with its ribosome binding site. dszABC Translational coupling, in turn, prevents translation of the downstream genes. The silencer combined with translational coupling thus represents an effective way of preventing expression of operons when spuriously transcribed from upstream promoters.

Martínez, L., Santoro, G., Merino, P., Accolla, M., Lauwaet, K., Sobrado, J., Sabbah, H., Pelaez, R.J., Herrero, V.J., Tanarro, I., Agúndez, M., Martín-Jimenez, A., Otero, R., Ellis, G.J., Joblin, C., Cernicharo, J., Martín-Gago, J.A., 2020. Prevalence of non-aromatic carbonaceous molecules in the inner regions of circumstellar envelopes. Nature Astronomy 4, 97-105.

https://doi.org/10.1038/s41550-019-0899-4 Evolved stars are foundries of chemical complexity, gas and dust that provide the building blocks of planets and life, and dust nucleation first occurs in their photosphere. The circumstellar regions enveloping these stars, despite their importance, remain hidden to many observations, and dust formation processes are therefore still poorly understood. Laboratory astrophysics provides complementary routes to unveil these chemical processes, but most experiments rely on combustion or plasma decomposition of molecular precursors under physical conditions far removed from those in space. To reproduce and characterize the bottom-up dust formation process, we have built an ultra-high vacuum machine combining atomic gas aggregation with advanced in situ characterization techniques. We show that carbonaceous dust analogues that formed from low-pressure gas- phase condensation of carbon atoms in a hydrogen atmosphere, in a ratio of carbon to molecular hydrogen similar to that reported for evolved stars, lead to the formation of amorphous carbon nanograins and aliphatic carbon clusters. Aromatic species and fullerenes do not form effectively under these conditions, raising implications for a revision of the chemical mechanisms taking place in circumstellar envelopes.

Martins, L.L., Schulz, H.-M., Severiano Ribeiro, H.J.P., Nascimento, C.A.d., Souza, E.S.d., Cruz, G.F.d., 2020. Cadalenes and norcadalenes in organic-rich shales of the Permian Irati Formation (Paraná Basin, Brazil): Tracers for terrestrial input or also indicators of temperature-controlled organic-inorganic interactions? Organic Geochemistry 140, 103962.

http://www.sciencedirect.com/science/article/pii/S0146638019301998 Cadalene, isocadalene and a series of norcadalenes were identified in black shales of the Permian Irati Formation in the northeastern and central eastern Paraná Basin (Brazil). The origin of their α -isomers with an isopropyl substituent is potentially related to higher plants, and likely reflects the spreading of pteridophytes and gymnosperms after the glaciation of southern Gondwana. A general increase in the relative abundance of isocadalene (1,6-dimethyl-3- isopropylnaphthalene, the β -isomer) co-occurs in with increasing thermal maturity at the base of the Amaral Machado Quarry (northeastern basin), and refers to the acid-catalyzed rearrangement of cadalene (1,6-dimethyl-4- isopropylnaphthalene, the α -isomer) due to the presence of montmorillonite, via an