Abstract
Metabolomics is a tool with immense potential for providing insight into the impact of biological processes on the environment. Here, we used metabolomics methods to characterize intracellular metabolites within marine microorganisms during a manipulation experiment that was designed to test the impact of two sources of microbial mortality, protozoan grazing and viral lysis. Intracellular metabolites were analyzed with targeted and untargeted mass spectrometry methods. The treatment with reduced viral mortality showed the largest changes in metabolite concentrations, although there were organic compounds that shifted when the impact of protozoan grazers was reduced. Intracellular concentrations of guanine, phenylalanine, glutamic acid, and ectoine presented significant responses to changes in the source of mortality. Unexpectedly, variability in metabolite concentrations were not accompanied by increases in microbial abundance which indicates that marine microorganisms altered their internal organic carbon stores without changes in biomass or microbial growth. We used Weighted Correlation Network Analysis (WGCNA) to identify correlations between the targeted and untargeted mass spectrometry data. This analysis revealed multiple unknown organic compounds were correlated with compatible solutes, also called osmolytes or chemical chaperones, which emphasizes the dominant role of compatible solutes in marine microorganisms.
Highlights
The actions of microbial-sized cells impact the composition of organic carbon found in marine ecosystems
The total organic carbon concentrations within the incubation bottles ranged from 69–86 μM, with slight variability at the onset of the experiment and across the different experimental treatments (Table 1)
Marine microorganisms play a critical role in biogeochemical cycling because they consume, alter, and release organic matter
Summary
The actions of microbial-sized cells impact the composition of organic carbon found in marine ecosystems. Heterotrophic microorganisms use organic matter as energy and carbon sources, and this process consumes and alters organic matter e.g., [3,4]. These heterotrophic microorganisms are subsequently consumed by predators which transfers organic carbon to larger members of a marine food web. The vast size of the worlds’ oceans and the amount of carbon they hold makes these processes important components of the global carbon cycle. Marine scientists regularly use manipulation experiments to quantify microbial processes within the marine carbon cycle and to characterize the organic carbon transferred within marine food webs
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