S19-1

The Mechanism of Aniline Blue Degradation by Short-Chain Dehydrogenase (SDRz) in Comamonas testosteroni

Dye wastewater pollution, particularly from persistent and toxic polycyclic organic pollutants, such as aniline blue, poses a significant environmental challenge. Aniline blue, a triphenylmethane dye widely used in the textile, leather, paper, and pharmaceutical industries, is notoriously difficult to treat owing to its complex structure and potential for bioaccumulation. In this study, we explored the capacity of Comamonas testosteroni (CT1) to efficiently degrade aniline blue, focusing on the underlying enzymatic mechanisms and degradation pathways. Through prokaryotic transcriptome analysis, we identified a significantly upregulated short-chain dehydrogenase (SDRz) gene (log2FC = 2.11, p < 0.05) that plays a crucial role in the degradation process. The SDRz enzyme possessed highly conserved motifs and a typical short-chain dehydrogenase structure. Functional validation using an SDRz-knockout strain (CT-ΔSDRz) and an SDRz-expressioning strains (E-SDRz) confirmed that SDRz is essential for aniline blue degradation. The knockout strain CT-ΔSDRz exhibited a 1.27-fold reduction in the degradation efficiency, compared to CT1 strain after 12 h; while the expression strain E-SDRz showed a 1.24-fold increase compared to Escherichia coli DH5α after 12 h. Recombinant SDRz (rSDRz) was successfully produced, showing significant enzymatic activity (1.267 ± 0.04 mmol·L-1·min-1 protein), with kinetic parameters Vmax = 2.870 ± 0.0156 mmol·L⁻1·min⁻1 protein and Km = 1.805 ± 0.0128 mM·mL-1. Under optimal conditions, the rSDRz achieved a degradation efficiency of 62.17% for aniline blue. Gas chromatography-mass spectrometry (GC-MS) analysis identified several intermediate metabolites in the degradation pathway, including benzeneacetaldehyde, a, a-diphenyl, 2-amino-4-methylbenzophenone, benzene, 1-dimethylamino-4-phenylmethyl, benzenesulfonic acid, methyl ester, further elucidating the biodegradation mechanism. These findings highlight SDRz as a critical enzyme in the biodegradation of aniline blue, offering valuable insights and a robust theoretical foundation for developing advanced bioremediation strategies to address dye wastewater pollution.

Unlocking the potential of soil microbial communities for bioremediation of emerging organic contaminants: omics-based approaches

The remediation of emerging contaminants presents a pressing environmental challenge, necessitating innovative approaches for effective mitigation. This review article delves into the untapped potential of soil microbial communities in the bioremediation of emerging contaminants. Bioremediation, while a promising method, often proves time-consuming and requires a deep comprehension of microbial intricacies for enhancement. Given the challenges presented by the inability to culture many of these microorganisms, conventional methods are inadequate for achieving this goal. While omics-based methods provide an innovative approach to understanding the fundamental aspects, processes, and connections among microorganisms that are essential for improving bioremediation strategies. By exploring the latest advancements in omics technologies, this review aims to shed light on how these approaches can unlock the hidden capabilities of soil microbial communities, paving the way for more efficient and sustainable remediation solutions.

New insights into xenobiotic tolerance of Antarctic bacteria: transcriptomic analysis of Pseudomonas sp. TNT3 during 2,4,6-trinitrotoluene biotransformation

The xenobiotic 2,4,6-trinitrotoluene (TNT) is a highly persistent environmental contaminant, whose biotransformation by microorganisms has attracted renewed attention. In previous research, we reported the discovery of Pseudomonas sp. TNT3, the first described Antarctic bacterium with the ability to biotransform TNT. Furthermore, through genomic analysis, we identified distinctive features in this isolate associated with the biotransformation of TNT and other xenobiotics. However, the metabolic pathways and genes active during TNT exposure in this bacterium remained unexplored. In the present transcriptomic study, we used RNA-sequencing to investigate gene expression changes in Pseudomonas sp. TNT3 exposed to 100 mg/L of TNT. The results showed differential expression of 194 genes (54 upregulated and 140 downregulated), mostly encoding hypothetical proteins. The most highly upregulated gene (> 1000-fold) encoded an azoreductase enzyme not previously described. Other significantly upregulated genes were associated with (nitro)aromatics detoxification, oxidative, thiol-specific, and nitrosative stress responses, and (nitro)aromatic xenobiotic tolerance via efflux pumps. Most of the downregulated genes were involved in the electron transport chain, pyrroloquinoline quinone (PQQ)-related alcohol oxidation, and motility. These findings highlight a complex cellular response to TNT exposure, with the azoreductase enzyme likely playing a crucial role in TNT biotransformation. Our study provides new insights into the molecular mechanisms of TNT biotransformation and aids in developing effective TNT bioremediation strategies. To the best of our knowledge, this report is the first transcriptomic response analysis of an Antarctic bacterium during TNT biotransformation.