A Cyanide Tailings Management Method Using Pseudomonas Fluorescens to Improve Conventional Treatments for Progressive Closure at Small Gold Mines

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.Based on the review of different research studies, we could assess that, due to their unique biological features, microbes, specifically bacteria, could be used to repair damaged soils with heavy metal and toxic compound contents. Furthermore, these microorganisms are metabolically capable to oxidize cyanide and its by-products to generate less-toxic compounds at the end of the process. This research proposal seeks to improve conventional mine closure designs, thus counteracting their negative short-term, medium-term, and long-term after-effects to the environment. The proposed technique as a solution, therefore, is microbial remediation, using pseudomonas fluorescens bacteria to oxidize this compound to non-toxic components. It will ensure operational continuity for the deposits and, in turn, the sustainability of the entire mining industry

The Paracoccus denitrificans NarK-like nitrate and nitrite transporters; probing nitrate uptake and nitrate/nitrite exchange mechanisms

Nitrate and nitrite transport across biological mem branes is often facilitated by protein transporters that are members of the major facilita tor superfamily. Paracoccus denitrificans contains an unusual arrangement whereby two of the se transporters, NarK1 and NarK2, are fused into a single protein, N arK, which delivers nitrate to the respiratory nitrate reductase and transfers the pro duct, nitrite, to the periplasm. Our complementation studies, using a mutant lacking the nitrate/proton symporter NasA from the assimilatory nitrate reductase pathway, su pport that NarK1 functions as a nitrate/proton symporter while NarK2 is a nitrate/n itrite antiporter. Through the same experimental system, we find that Escherichia coli NarK and NarU can complement deletions in both narK and nasA in P. denitrificans , suggesting that, while these proteins are most likely nitrate/nitrite antiporters, they c an also act in the net uptake of nitrate. Finally, we argue that primary sequence analysis an d structural modelling do not readily explain why NasA, NarK1 and NarK2, as well as other transporters from this protein family, have such different functions, ranging from net nitrate uptake to nitrate/nitrite exchange

Transcriptional and translational adaptation to aerobic nitrate anabolism in the denitrifier Paracoocus denitrificans

Transcriptional adaptation to nitrate-dependent anabolism by Paracoccus denitrificans PD1222 was studied. A total of 74 genes were induced in cells grown with nitrate as N-source compared to ammonium, including nasTSABGHC and ntrBC genes. The nasT and nasS genes were cotranscribed, although nasT was more strongly induced by nitrate than nasS. The nasABGHC genes constituted a transcriptional unit, which is preceded by a non-coding region containing hairpin structures involved in transcription termination. The nasTS and nasABGHC transcripts were detected at similar levels with nitrate or glutamate as N-source1 but nasABGHC transcript was undetectable in ammonium-grown cells. The nitrite reductase NasG subunit was detected by 2D-PAGE in cytoplasmic fractions from nitrate-grown cells, but it was not present when either ammonium or glutamate was used as N-source. The nasT mutant lacked both nasABGHC transcript and NADH-dependent nitrate reductase activity. On the contrary, the nasS mutant showed similar levels of the nasABGHC transcript to the wild-type strain and displayed NasG protein and NADH-nitrate reductase activity with all N-sources tested, except with ammonium. Ammonium repression of nasABGHC was dependent on the Ntr system. The ntrBC and ntrYX genes were expressed at low levels regardless of the nitrogen source supporting growth. Mutational analysis of the ntrBCYX genes indicated that while ntrBC genes are required for nitrate assimilation, ntrYX genes can only partially restore growth on nitrate in absence of ntrBC genes. The existence of a regulation mechanism for nitrate assimilation in P. denitrificans, by which nitrate induction operates at both transcriptional and translational levels, is proposed