The issues of climate change, land degradation, and sustainable agriculture
are arguably three of the most significant scientific, political, and environmental
challenges of the 21st century. However, one common denominator that is frequently
overlooked when trying to understand and respond to key processes in the environment
is the role of soil microbial biomass. As an example, soil microbial biomass controls
the production of soil organic matter—the largest pool of terrestrial carbon—which is
an important variable in studies of climate change and is also central to sustainable
agriculture. Traditionally, the complex nature of this biomaterial renders it difficult to
study at sufficiently fine resolution. At the molecular level, NMR spectroscopy is the
single most powerful analytical technique available for the determination of structural
components and their interactions in various environmental matrices, and can be
performed on components of different physical phases [solids, semi-solids (gels),
liquids, and gases]. NMR spectroscopy provides information about the chemical
environment of nuclei within a molecule, and the three most frequently studied nuclei
in microbial biomass are protons (1H), carbons (13C) and (15N). However, carbon and
nitrogen NMR are generally considered relatively insensitive analytical techniques,
because at natural abundance only 1% of the total carbon (13C) and 0.37% of the total
nitrogen (15N) is NMR observable, while 99.9% of all protons are detectable. The
complexity and multitude of components within a natural organic matter sample lead to
extensive spectral overlap, especially in solid-state NMR. Therefore, the
transformations of minor components are difficult to monitor unless we enhance NMR
sensitivity by increasing the relative abundance of 13C and 15N through isotopic
enrichment. This chapter provides an overview of the application of various NMR
techniques used to provide comprehensive molecular and structural information, as
well as some of the key considerations in the field of microbial biogeochemistry.
Keywords: Carbon, Degradation, Microbial biomass, Nitrogen, Nuclear magnetic
resonance spectroscopy, Soils.Carbon, Degradation, Microbial biomass, Nitrogen, Nuclear magnetic
resonance spectroscopy, Soils.
