Abstract
Diclofenac (DCF) constitutes one of the most significant ecopollutants detected in various environmental matrices. Biological clean-up technologies that rely on xenobiotics-degrading microorganisms are considered as a valuable alternative for chemical oxidation methods. Up to now, the knowledge about DCF multi-level influence on bacterial cells is fragmentary. In this study, we evaluate the degradation potential and impact of DCF on Pseudomonas moorei KB4 strain. In mono-substrate culture KB4 metabolized 0.5 mg L−1 of DCF, but supplementation with glucose (Glc) and sodium acetate (SA) increased degraded doses up to 1 mg L−1 within 12 days. For all established conditions, 4′-OH-DCF and DCF-lactam were identified. Gene expression analysis revealed the up-regulation of selected genes encoding biotransformation enzymes in the presence of DCF, in both mono-substrate and co-metabolic conditions. The multifactorial analysis of KB4 cell exposure to DCF showed a decrease in the zeta-potential with a simultaneous increase in the cell wall hydrophobicity. Magnified membrane permeability was coupled with the significant increase in the branched (19:0 anteiso) and cyclopropane (17:0 cyclo) fatty acid accompanied with reduced amounts of unsaturated ones. DCF injures the cells which is expressed by raised activities of acid and alkaline phosphatases as well as formation of lipids peroxidation products (LPX). The elevated activity of superoxide dismutase (SOD) and catalase (CAT) testified that DCF induced oxidative stress.
Highlights
Diclofenac (DCF), a phenylacetic acid derivative classified as a non-steroidal anti-inflammatory drug (NSAID), due to wide prevalence is considered as one of the most important contaminants of emerging concern
Based on the literature data about the most frequently occurring microbial DCF by-products, we confirmed the formation of 4 -hydroxylated DCF (4 -OH-DCF) and generated during intramolecular ring closure DCF-lactam in both mono-substrate and co-metabolic cultures (Figure S1)
Despite the observed degradation of DCF in mono-substrate culture, the increase in the number of cells for this system was not observed, which indicated that the KB4 is not able to proliferate in the presence of DCF as a sole carbon and energy source., The most significant cell proliferation has been observed for co-metabolic conditions with Glc and for Glc and sodium acetate (SA)
Summary
Diclofenac (DCF), a phenylacetic acid derivative classified as a non-steroidal anti-inflammatory drug (NSAID), due to wide prevalence is considered as one of the most important contaminants of emerging concern. The presence of DCF in drinking [1,2,3], ground [4,5] or surface water [6,7], as well as sewage [8] and activated sludge [9,10] ranged from 0.02 ng L−1 to 20 μg L−1 [2]. The usefulness of traditional physico-chemical sewage treatment methods applied to the removal of recalcitrant pollutants is being increasingly questioned [2]. Bioremediation is an eco-safe and economically justified alternative for harsh chemical treatments being based on the individual microbial strain able to detoxify the particular compound or microbial consortia with more complex metabolic properties. The ecological success of pseudomonads can be attributed to great metabolic versatility, effective detoxifying and adapting mechanisms based on the high oxidoreductase activities, adjusting the membranes fluidity or extensive transport, and secretion systems [15]
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