Benzimidazole fungicide biotransformation by comammox Nitrospira bacteria: Transformation pathways and associated proteomic responses

Deciphering the role of nitric oxide in mitigation of systemic fungicide induced growth inhibition and oxidative damage in wheat

Consento (CON) poses a significant environmental hazard as a systemic fungicide, adversely affecting the health of non-target organisms. Nitric oxide (NO), a signaling molecule, is known to play a crucial role in plant physiology and abiotic stress tolerance. However, whether NO plays any role to enhance fungicide CON tolerance in wheat seedlings is yet unclear. Therefore, we conducted a hydroponic experiment i) to investigate the morpho-physio-biochemical changes of wheat seedlings to fungicide CON stress, and ii) to examine the effects of NO and fungicide CON treatments on oxidative damage, antioxidant system, secondary metabolism and detoxification of systemic fungicide in wheat seedlings. The results showed that CON fungicide at the highest (4X) concentration significantly decreased wheat seedlings fresh weight (46.89%), shoot length (40.26%), root length (56.11%) and total chlorophyll contents (67.44%) in a dose response relationship. Moreover, CON significantly increased hydrogen peroxide, malondialdehyde, catalase, ascorbate peroxidase, glutathione-S-transferase, and peroxidase activities while decreased reduced glutathione (GSH) content. This ultimately impaired the redox homeostasis of cells, leading to oxidative damage in cell membrane. Under fungicide treatment, the addition of NO reduced the fungicide phytotoxicity, with an increase of over 60% in seedling growth. The NO application mitigated CON phytotoxicity as reflected by significantly increased chlorophyll pigments (69.88%) and decreased oxidative damage in wheat leaves. Indeed, the NO alleviatory effect was able to increase the tolerance of seedlings to fungicide, which resulted increments in antioxidant and detoxification enzymes activity, with the enhanced GSH level (78.54%). Interestingly, NO alleviated CON phytotoxicity through the phenylpropanoid pathway by enhancing the activity of secondary metabolism enzymes such as phenylalanine ammonia-lyase (47.28%), polyphenol oxidase (9%), and associated metabolites such as phenolic acids (77.62%), flavonoids (34.33%) in wheat leaves. Our study has provided evidence that NO plays a key role in the metabolism and detoxification of systemic fungicide in wheat through enhanced activity of antioxidants, detoxifications and secondary metabolic enzymes.

Substrate promiscuity of xenobiotic-transforming hydrolases from stream biofilms impacted by treated wastewater

Organic contaminants enter aquatic ecosystems from various sources, including wastewater treatment plant effluent. Freshwater biofilms play a major role in the removal of organic contaminants from receiving water bodies, but knowledge of the molecular mechanisms driving contaminant biotransformations in complex stream biofilm (periphyton) communities remains limited. Previously, we demonstrated that biofilms in experimental flume systems grown at higher ratios of treated wastewater (WW) to stream water displayed an increased biotransformation potential for a number of organic contaminants. We identified a positive correlation between WW percentage and biofilm biotransformation rates for the widely-used insect repellent, N,N-diethyl-meta-toluamide (DEET) and a number of other wastewater-borne contaminants with hydrolyzable moieties. Here, we conducted deep shotgun sequencing of flume biofilms and identified a positive correlation between WW percentage and metagenomic read abundances of DEET hydrolase (DH) homologs. To test the causality of this association, we constructed a targeted metagenomic library of DH homologs from flume biofilms. We screened our complete metagenomic library for activity with four different substrates, including DEET, and a subset thereof with 183 WW-related organic compounds. The majority of active hydrolases in the metagenomic library preferred aliphatic and aromatic ester substrates while, remarkably, only a single reference enzyme was capable of DEET hydrolysis. Of the 626 total enzyme-substrate combinations tested, approximately 5% were active enzyme-substrate pairs. Metagenomic DH family homologs revealed a broad substrate promiscuity spanning 22 different compounds when summed across all enzymes tested. We biochemically characterized the most promiscuous and active enzymes identified based on metagenomic analysis from uncultivated Rhodospirillaceae and Planctomycetaceae. In addition to characterizing new DH family enzymes, we exemplified a framework for linking metagenome-guided hypothesis generation with experimental validation. Overall, this study expands the scope of known enzymatic contaminant biotransformations for metagenomic hydrolases from WW-receiving stream biofilm communities.

Mechanochemistry Frees Thiourea Dioxide (TDO) from the 'Veils' of Solvent, Exposing All Its Reactivity

The synthesis of nitrogen-based heterocycles has always been considered essential in developing pharmaceuticals in medicine and agriculture. This explains why various synthetic approaches have been proposed in recent decades. However performing as methods, they often imply harsh conditions or the employment of toxic solvents and dangerous reagents. Mechanochemistry is undoubtedly one of the most promising technologies currently used for reducing any possible environmental impact, addressing the worldwide interest in counteracting environmental pollution. Following this line, we propose a new mechanochemical protocol for synthesizing various heterocyclic classes by exploiting thiourea dioxide (TDO)'s reducing proprieties and electrophilic nature. Simultaneously exploiting the low cost of a component of the textile industry such as TDO and all the advantages brought by a green technique such as mechanochemistry, we plot a route towards a more sustainable and eco-friendly methodology for preparing heterocyclic moieties.