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Sánchez Andrea, Irene

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Irene
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Sánchez Andrea
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IE University
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IE School of Science & Technology
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Environmental Sciences
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    A novel mechanism for dissimilatory nitrate reduction to ammonium in Acididesulfobacillus acetoxydans
    (American Society for Microbiology, 2024) Egas, Reinier; Kurth, Julia; Boeren, Sjef; Sousa, Diana; Welte, Cornelia; Sánchez Andrea, Irene; Ministerie van Onderwijs, Cultuur en Wetenschap; https://ror.org/02jjdwm75
    The biological route of nitrate reduction has important implications for the bioavailability of nitrogen within ecosystems. Nitrate reduction via nitrite,either to ammonium (ammonification) or to nitrous oxide or dinitrogen (denitrification),determines whether nitrogen is retained within the system or lost as a gas. The acidophilic sulfate-reducing bacterium (aSRB) Acididesulfobacillus acetoxydans can perform dissimilatory nitrate reduction to ammonium (DNRA). While encoding a Nar-type nitrate reductase,A. acetoxydans lacks recognized nitrite reductase genes. In this study,A. acetoxydans was cultivated under conditions conducive to DNRA. During cultivations,we monitored the production of potential nitrogen intermediates (nitrate,nitrite,nitric oxide,hydroxylamine,and ammonium). Resting cell experiments were performed with nitrate,nitrite,and hydroxylamine to confirm their reduction to ammonium,and formed intermediates were tracked. To identify the enzymes involved in DNRA,comparative transcriptomics and proteomics were performed with A. acetoxydans growing under nitrate- and sulfate-reducing conditions. Nitrite is likely reduced to ammonia by the previously undescribed nitrite reductase activity of the NADH-linked sulfite reductase AsrABC,or by a putatively ferredoxin-dependent homolog of the nitrite reductase NirA (DEACI_1836),or both. We identified enzymes and intermediates not previously associated with DNRA and nitrosative stress in aSRB. This increases our knowledge about the metabolism of this type of bacteria and helps the interpretation of (meta)genome data from various ecosystems on their DNRA potential and the nitrogen cycle. © 2024 Egas et al.
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    Acetic acid stress response of the acidophilic sulfate reducer Acididesulfobacillus acetoxydans
    (John Wiley and Sons Inc, 2024) Egas, Reinier; Sahonero Canavesi, Diana; Bale, Nicole; Koenen, Micel; Yildiz, Çaglar; Villanueva, Laura; Sousa, Diana; Sánchez Andrea, Irene; Ministerie van Onderwijs, Cultuur en Wetenschap; https://ror.org/02jjdwm75
    Acid mine drainage (AMD) waters are a severe environmental threat,due to their high metal content and low pH (pH <3). Current technologies treating AMD utilize neutrophilic sulfate-reducing microorganisms (SRMs),but acidophilic SRM could offer advantages. As AMDs are low in organics these processes require electron donor addition,which is often incompletely oxidized into organic acids (e.g.,acetic acid). At low pH,acetic acid is undissociated and toxic to microorganisms. We investigated the stress response of the acetotrophic Acididesulfobacillus acetoxydans to acetic acid. A. acetoxydans was cultivated in bioreactors at pH 5.0 (optimum). For stress experiments,triplicate reactors were spiked until 7.5 mM of acetic acid and compared with (non-spiked) triplicate reactors for physiological,transcriptomic,and membrane lipid changes. After acetic acid spiking,the optical density initially dropped,followed by an adaptation phase during which growth resumed at a lower growth rate. Transcriptome analysis revealed a downregulation of genes involved in glutamate and aspartate synthesis following spiking. Membrane lipid analysis revealed a decrease in iso and anteiso fatty acid relative abundance; and an increase of acetyl-CoA as a fatty acid precursor. These adaptations allow A. acetoxydans to detoxify acetic acid,creating milder conditions for other microorganisms in AMD environments. © 2024 The Authors. Environmental Microbiology published by Applied Microbiology International and John Wiley & Sons Ltd.