Bugs on drugs: the microbially mediated fate of pharmaceuticals in anoxic environments
Creators: name: Zeliph, Michelle Laura
Publisher: name: No Publisher Supplied
Year: 2022

description: Pharmaceuticals and personal care products (PPCPs) are emerging contaminants in aquatic ecosystems throughout the world. These compounds are biologically active and can thus pose a risk to the health and survival of aquatic biota. It is widely known that microorganisms play an important role in the biodegradation of pollutant chemicals in the environment, however, PPCP biodegradation experiments have mainly focused on aerobic conditions relevant to activated sludge in wastewater treatment plants (WWTPs). There remains limited information on PPCP biodegradation, potential transformation products, and the microorganisms responsible for these processes in anoxic environments (e.g., aquatic sediments or WWTP anaerobic sludge digesters). The major goal of this study was to determine how environmental conditions, including redox, PPCP input, and salinity, impact the biodegradability of select PPCP compounds and the bacterial communities responsible for their degradation in anoxic estuarine sediments and WWTP sludge. It was hypothesized that both the extent of biodegradation and the microorganisms responsible would be dependent on the site conditions and structure of the PPCP compound. Anaerobic cultures to determine rates and extent of degradation were established using sediment from the Arthur Kill, Hudson River, Jiulong River, and Raritan River, and activated sludge from a Central New Jersey WWTP in minimal salts medium supplemented with sulfate, nitrate, or carbonate to promote sulfidogenic, denitrifying, or methanogenic conditions, respectively. Cultures were spiked with a single analgesic/antipyretic compound (acetaminophen, aspirin, diclofenac, or ibuprofen). Degradation and transformation of these compounds were monitored by high performance liquid chromatography. Similar PPCP degradation profiles were observed across these sites, therefore PPCP-degrading bacteria appear to be globally distributed. Acetaminophen and aspirin were found to be readily degradable, while diclofenac and ibuprofen were recalcitrant. Active aspirin-degrading cultures in sulfidogenic medium were enriched and ribosomal RNA operon analysis via the Oxford Nanopore MinION system was used to characterize and quantify bacterial community members. Different species of bacteria with diverse metabolisms were responsible for aspirin degradation and varied based on the source of inoculum. Dominant bacterial community members thought to be involved in aspirin degradation were identified as most closely related to Desulfatiglans anilini in the Hudson River, Syntrophus aciditrophicus and Syntrophobacter fumaroxidans in the Raritan River, and Desulfococcus multivorans bacteria in the Central NJ WWTP.To examine the potential effects of an urbanization and freshwater-estuarine gradient on PPCP degradation, microcosms were established using sediment and site water collected along a freshwater-estuarine gradient from both the Hudson River and Raritan River. These cultures were spiked with a combination of the four pharmaceutical compounds. Aspirin and acetaminophen were again found to be readily degradable, but interestingly, anaerobic ibuprofen degradation was observed in Hudson River cultures and diclofenac transformation was observed in Hudson River cultures and some Raritan River cultures. The bacterial communities in enriched aspirin- and acetaminophen-degrading Raritan River cultures were found to differ depending on the PPCP, but community profiles were similar along the freshwater-estuarine gradient.This study highlights the potential for anaerobic degradation and transformation of PPCPs by bacterial communities around the world and identifies several community members which play a key role in aspirin and acetaminophen degradation. Additional work is needed to isolate anaerobic PPCP-degrading organisms and subsequently identify the metabolic pathways involved in anaerobic PPCP degradation.