Metabolite composition of sinking particles differs from surface suspended particles across a latitudinal transect in the South Atlantic

Abstract

Marine sinking particles transport carbon from the surface and bury it in deep‐sea sediments, where it can be sequestered on geologic time scales. The combination of the surface ocean food web that produces these particles and the particle‐associated microbial community that degrades them creates a complex set of variables that control organic matter cycling. We use targeted metabolomics to characterize a suite of small biomolecules, or metabolites, in sinking particles and compare their metabolite composition to that of the suspended particles in the euphotic zone from which they are likely derived. These samples were collected in the South Atlantic subtropical gyre, as well as in the equatorial Atlantic region and the Amazon River plume. The composition of targeted metabolites in the sinking particles was relatively similar throughout the transect, despite the distinct oceanic regions in which they were generated. Metabolites possibly derived from the degradation of nucleic acids and lipids, such as xanthine and glycine betaine, were an increased mole fraction of the targeted metabolites in the sinking particles relative to surface suspended particles, while algal‐derived metabolites like the osmolyte dimethylsulfoniopropionate were a smaller fraction of the observed metabolites on the sinking particles. These compositional changes are shaped both by the removal of metabolites associated with detritus delivered from the surface ocean and by production of metabolites by the sinking particle‐associated microbial communities. Furthermore, they provide a basis for examining the types and quantities of metabolites that may be delivered to the deep sea by sinking particles.

Intracellular Metabolites in Marine Microorganisms during an Experiment Evaluating Microbial Mortality

“…Regardless, our observation of the key role of compatible solutes from both the targeted and untargeted metabolomics datasets aligns with genetic information indicating that an abundant marine microorganism, SAR11, dedicates a large component of its resources to the use of compatible solutes [38]. The combination of genomic data, our previous observations of increasing concentrations of compatible solutes in sinking marine particles [39], and the results from the current project collectively indicate that compatible solutes are critical component of organic matter within marine microorganisms.…”

Particulate Organic Carbon Deconstructed: Molecular and Chemical Composition of Particulate Organic Carbon in the Ocean

“…Identifying MUC sources and cycling is an area that merits further attention, but may be better addressed in the future through application of high-resolution or ultra-high-resolution mass spectrometry, as well as high-resolution solid-state NMR (Mao et al, 2011), which have the potential to expand the analytical window to simultaneously examine the molecular diversity of important compound classes (e.g., lipids), and also to identify novel structures or functional groups. Within DOC, new analytical tools and workflows are enabling structural information to be assigned for a growing number of molecular features (e.g., Petras et al, 2017), and metabolomics approaches also are beginning to be applied to POC (Johnson et al, 2020).…”

Analytical and Computational Advances, Opportunities, and Challenges in Marine Organic Biogeochemistry in an Era of “Omics”

“…Small polar intermediates in this last biochemical class have received attention in the last 5 years as advances in sample acquisition, liquid chromatography, and mass spectrometry have expanded the analytical window of marine organic compounds. These compounds can be detected and quantified in both dissolved (Johnson et al, 2017) and particulate (Durham et al, 2019;Johnson et al, 2020) pools, and include molecules such as growth substrates, metabolic cofactors, and signaling molecules (the collective is often referred to as "metabolites, " inferring a biological origin and sink).…”

“…Early studies have used diversity analysis to connect culture-based metabolic inferences with metabolite analyses (Allen et al, 2008;Johnson et al, 2016;Heal et al, 2017). Field studies are connecting community composition (and inferred metabolic potential) with metabolite concentrations to postulate microbe-microbe interactions (Durham et al, 2019) and OM-related processes (Johnson et al, 2020). This field is rapidly expanding with new method developments presented at major conferences; significant advances in our understanding of microbe-microbe interactions through chemical exchange are likely in the near future.…”