White Rot Fungi Produce Novel Tire Wear Compound Metabolites and Reveal Underappreciated Amino Acid Conjugation Pathways

Abstract

There is increasing concern about tire wear compounds (TWCs) in surface water and stormwater as evidence grows on their toxicity and widespread detection in the environment. Because TWCs are prevalent in stormwater, there is a need to understand fate and treatment options including biotransformation in green infrastructure (e.g., bioretention). Particularly, fungal biotransformation is not well-studied in a stormwater context despite the known ability of certain fungi to remove recalcitrant contaminants. Here, we report the first study on fungal biotransformation of the TWCs acetanilide and hexamethoxymethylmelamine (HMMM). We found that the model white rot fungus, Trametes versicolor, removed 81.9% and 69.6% of acetanilide and HMMM, respectively, with no significant sorption to biomass. The bicyclic amine 1,3-diphenylguanidine was not removed. Additionally, we identified novel TWC metabolites using semi-untargeted metabolomics via high-resolution mass spectrometry. Key metabolites include multiple isomers of HMMM biotransformation products, melamine as a possible “dead-end” product of HMMM (verified with an authentic standard), and a glutamine-conjugated product of acetanilide. These metabolites have implications for environmental toxicity and treatment. Our discovery of the first fungal glutamine-conjugated product highlights the need to investigate amino acid conjugation as an important pathway in biotransformation of contaminants, with implications in other fields including natural products discovery.

Rapid plant uptake of isothiazolinone biocides and formation of metabolites by hydroponic Arabidopsis

“…We propose a BIT–amino acid conjugate (BIT–alanine–tyrosine) as a possible structure for another of the compounds upregulated in BIT-exposed plant tissue vs. unexposed plant tissue (at a seven-fold increase). The mass deviation of this compound is 8 ppm, with a level 3b confidence 67 based on MS fragments (no MS2 data) and experimental data. Structures in Table 1 are shown in their unionized state for consistency; however, we would expect (based on the accurate mass measured) that the compound is likely deprotonated in the at ambient conditions (p K a = 4.0) 85 and tyrosine is known to ionize in either ESI+ or ESI− modes.…”

“…78 Thus, the upregulated nicotinic acid in BIT-exposed plants may be due to the increased NADPH needed for glutathione conjugation, [79][80][81] cytochrome P450, 82 or other processes potentially related to detoxication metabolism. The other endogenous plant compound signicantly upregulated (11-fold in plant tissue, 472-fold in hydroponic medium) we propose as phenylthioacetohydroximic acid (mass deviation of 3 ppm; 3a condence 67 ). Phenylthioacetohydroximic acid is part of the glucotropaeolin synthesis pathway.…”

“…The extracted plant tissues (extraction details in the ESI†) were analyzed on a Thermo Q-Exactive Orbitrap High-Resolution Mass Spectrometer using Full MS scans with data-dependent MS/MS acquisition, in the manner of previous literature. 67 Both ESI positive and negative modes were used. Polarity switching was used for the MS scan ( i.e.…”

“…The mobile phase gradients are given in the ESI. † The 67 Both ESI positive and negative modes were used. Polarity switching was used for the MS scan (i.e., both positive and negative modes were run in the same sample run).…”

Uptake, Metabolism, and Accumulation of Tire Wear Particle-Derived Compounds in Lettuce

“…This paper joins a growing body of evidence showing that amino acid conjugation is a relevant biological transformation for xenobiotics. 12,24,25,40 Some of these novel transformation products of HMMM may be uniquely formed within plants, and we measured four transformation products of HMMM with high intensity, all of which were stable in the leaves over the duration of our experiment. BTZ was metabolized remarkably quickly in the lettuce leaves.…”