Pharmaceutical Biotransformation is Influenced by Photosynthesis and Microbial Nitrogen Cycling in a Benthic Wetland Biomat

Abstract

In shallow, open-water engineered wetlands, design parameters select for a photosynthetic microbial biomat capable of robust pharmaceutical biotransformation, yet the contributions of specific microbial processes remain unclear. Here, we combined genome-resolved metatranscriptomics and oxygen profiling of a field-scale biomat to inform laboratory inhibition microcosms amended with a suite of pharmaceuticals. Our analyses revealed a dynamic surficial layer harboring oxic−anoxic cycling and simultaneous photosynthetic, nitrifying, and denitrifying microbial transcription spanning nine bacterial phyla, with unbinned eukaryotic scaffolds suggesting a dominance of diatoms. In the laboratory, photosynthesis, nitrification, and denitrification were broadly decoupled by incubating oxic and anoxic microcosms in the presence and absence of light and nitrogen cycling enzyme inhibitors. Through combining microcosm inhibition data with field-scale metagenomics, we inferred microbial clades responsible for biotransformation associated with membrane-bound nitrate reductase activity (emtricitabine, trimethoprim, and atenolol), nitrous oxide reduction (trimethoprim), ammonium oxidation (trimethoprim and emtricitabine), and photosynthesis (metoprolol). Monitoring of transformation products of atenolol and emtricitabine confirmed that inhibition was specific to biotransformation and highlighted the value of oscillating redox environments for the further transformation of atenolol acid. Our findings shed light on microbial processes contributing to pharmaceutical biotransformation in open-water wetlands with implications for similar nature-based treatment systems.

Methane-Oxidizing Activity Enhances Sulfamethoxazole Biotransformation in a Benthic Constructed Wetland Biomat

“…24 Recently, we demonstrated an associative partial dependence of four pharmaceutical compounds on biomat photosynthesis, nitrification, and denitrification, speculating that methanotrophs could be involved in both methane and ammonia oxidation. 25 Combining this with earlier reports of abundant methanogens in anoxic biomat layers, 21,26 there is mounting evidence that methanotrophs may contribute to biogeochemical cycling and possibly contaminant attenuation in shallow, open-water constructed wetlands.…”

“…An analysis highlighting similarities between the 2020 biomat inoculum microbial community and 2018 field samples was conducted previously. 25 Oxic microcosms were categorized into three groups: no methane (41 mL air overpressure), low methane ∼50 μM (4.1 mL methane + 36.9 mL air overpressure), and high methane ∼200 μM (16.4 mL methane + 24.6 mL air overpressure). Aqueous methane concentrations were extrapolated from measured water column concentrations (September 2018, ∼2 to 12 μM) 31 assuming that biomat methane-oxidizing activity contributed significantly to decreasing upward methane fluxes.…”

Scalable and customizable parallel flow-through reactors to quantify biological processes related to contaminant attenuation by photosynthetic wetland microbial mats

“…While the depth of biomat and open water can be adjusted to experimental needs, we recommend adding at least 1 cm of biomat material to capture the diverse microbial consortia living both above and below the biomat oxic-anoxic interface, which is inferred to be within the surficial 1 cm of the biomat-water interface [13] . For the purposes of method validation with readily available data, biomat from the Prado Constructed Wetlands (Orange County, California) was used for seeding of the flow-through reactors.…”

“…We use a composition intended to replicate water from the Santa Ana River as sampled near Corona, CA ( Table 3 ). A portion of the Santa Ana is diverted into the Prado Constructed Wetlands, which contain UPOW cells of different configurations as well as vegetated cells [ 11 , 13 ]. Synthetic river water was supplemented with trace metals and silica to maintain microbial growth and resident diatoms.…”

“…This flow-through reactor design is better suited to mimic UPOW field conditions because of the continuous water flux, gravity-driven effluent removal, and the longevity of the system. Typical use cases include evaluating nutrient, pharmaceutical, and / or metal transformation under various operational conditions [13] . The final design ( Fig.…”