Nitric oxide-driven anaerobic oxidation of lignocellulose

Introduction

In the riparian zone of eutrophic lakes and in field denitrification beds, microbial communities degrade lignocellulose in anoxia while maintaining a denitrifying lifestyle. During this process, nitrate is converted to nitrogen gases via a series of reactions and intermediate products, fueled by the degradation of lignocellulosic biomass.

Knowledge Gap

The microbial interactions, metabolic pathways, and enzymatic mechanisms underlying this remarkable process remain largely unknown. Intriguingly, in these anoxic habitats, enzymes involved in O2-driven oxidative lignocellulose conversion are found and expressed. However, their source of O2, potential use of other oxidants, and catalytic mechanism in anoxia remain unknown.

Exploring this knowledge gap is a high-risk endeavor with the potential to discover yet undescribed enzymes or enzyme systems capable of anaerobic oxidation of lignocellulose (AOL).

Hypothesis

I hypothesize that oxidative cleavage of lignocellulose under denitrifying conditions follows aerobic routes, including:

1. Lytic polysaccharide monooxygenases (LPMOs)
2. Lignin-active oxidases

Furthermore, I propose that the activity of nitric oxide dismutases (NODs) provides a source of O2 for LPMOs and lignin-active enzymes. This is conceptually high risk, linking together biological processes in a new way.

Research Approach

Herein, I will scrutinize my key hypotheses by in-depth characterization of both LPMOs, lignin-active enzymes, and NODs to a depth never done before. I will study whether LPMOs can employ relevant non-conventional denitrification-linked electron acceptors and use novel approaches for characterizing the enigmatic NODs.

Significance

NOD-AOL is highly interdisciplinary and addresses questions central to understanding the global carbon and nitrogen cycles, which may ultimately help counteract climate change.