# Phenylpropanoid methyl esterase unlocks catabolism of aromatic biological nitrification inhibitors

## TL;DR

Scientists discovered a new microbial pathway that breaks down plant-produced inhibitors that reduce fertilizer nitrification, a process that contributes to greenhouse gas emissions.

## Contribution

The study identifies a novel phenylpropanoid methyl esterase enzyme and a microbial pathway for degrading aromatic nitrification inhibitors.

## Key findings

- A previously unknown microbial pathway for degrading phenylpropanoid methyl esters was identified.
- Two novel enzymes, including a phenylpropanoid methyl esterase, were found to direct these esters into known metabolic pathways.
- Transferring these genes into bacteria enabled them to use methyl esters as a carbon source.

## Abstract

Microbial nitrification of fertilizers represents is a significant global source of greenhouse gas emissions. This process increases emissions, fosters toxic algal blooms, and raises crop production costs. Some plants naturally release biological nitrification inhibitors to suppress ammonium-oxidizing microbes and reduce nitrification. Engineering nitrification inhibitor production into food and bioenergy crops via synthetic biology offers a promising mitigation strategy, but its success depends on addressing gaps in our understanding of inhibitor degradation in soil. This study begins to fill this gap by identifying a previously unknown microbial pathway for degrading phenylpropanoid methyl esters, a key class of aromatic nitrification inhibitors. Using transcriptomics and high-throughput functional genomics, we discovered genes essential for phenylpropanoid methyl ester degradation. Genetic and biochemical analyses revealed two novel enzymes, including a newly identified phenylpropanoid methyl esterase, that direct phenylpropanoid methyl esters into known metabolic pathways. Importantly, transferring these genes into bacteria capable of metabolizing other phenylpropanoids enabled them to use the methyl esters as a carbon source. This work provides critical insights into microbial nitrification inhibitor degradation, a poorly understood element of the nitrification cycle.