Wastewater bacteria remediating the pharmaceutical metformin: Genomes, plasmids and products

Betsy M. Martinez-Vaz, Anthony G. Dodge, Rachael M. Lucero, Randy B. Stockbridge, Ashley A. Robinson, Lambros J. Tassoulas, Lawrence P. Wackett

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Abstract

Metformin is used globally to treat type II diabetes, has demonstrated anti-ageing and COVID mitigation effects and is a major anthropogenic pollutant to be bioremediated by wastewater treatment plants (WWTPs). Metformin is not adsorbed well by activated carbon and toxic N-chloro derivatives can form in chlorinated water. Most earlier studies on metformin biodegradation have used wastewater consortia and details of the genomes, relevant genes, metabolic products, and potential for horizontal gene transfer are lacking. Here, two metformin-biodegrading bacteria from a WWTP were isolated and their biodegradation characterized. Aminobacter sp. MET metabolized metformin stoichiometrically to guanylurea, an intermediate known to accumulate in some environments including WWTPs. Pseudomonas mendocina MET completely metabolized metformin and utilized all the nitrogen atoms for growth. Pseudomonas mendocina MET also metabolized metformin breakdown products sometimes observed in WWTPs: 1-N-methylbiguanide, biguanide, guanylurea, and guanidine. The genome of each bacterium was obtained. Genes involved in the transport of guanylurea in Aminobacter sp. MET were expressed heterologously and shown to serve as an antiporter to expel the toxic guanidinium compound. A novel guanylurea hydrolase enzyme was identified in Pseudomonas mendocina MET, purified, and characterized. The Aminobacter and Pseudomonas each contained one plasmid of 160 kb and 90 kb, respectively. In total, these studies are significant for the bioremediation of a major pollutant in WWTPs today.

Original languageEnglish (US)
Article number1086261
JournalFrontiers in Bioengineering and Biotechnology
Volume10
DOIs
StatePublished - Dec 16 2022

Bibliographical note

Funding Information:
LT was supported on an Informatics Institute Fellowship from the University of Minnesota. Parts of this work were funded by Chemistry of Life Processes (CLP) Program of the National Science Foundation, grant no. 2203751 to LW and BM-V. and by R35 GM128768 to RS.

Funding Information:
LT was supported on an Informatics Institute Fellowship from the University of Minnesota. Parts of this work were funded by Chemistry of Life Processes (CLP) Program of the National Science Foundation, grant no. 2203751 to LW and BM-V. and by R35 GM128768 to RS.

Funding Information:
We thank Dean Young for help with the initial 1-N-methylbiguanide enrichment cultures and Adam Sealock (Metro Wastewater Treatment Plant in Saint Paul, MN) for providing sludge samples. Ashley Robinson and Dean Young were supported by Hamline University Summer Collaborative Research Program.

Publisher Copyright:
Copyright © 2022 Martinez-Vaz, Dodge, Lucero, Stockbridge, Robinson, Tassoulas and Wackett.

Keywords

  • Aminobacter
  • Pseudomonas
  • gdx
  • genomes
  • guanylurea
  • metformin
  • plasmids
  • transport

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