Polyamines are organic compounds with multiple amino groups. They are found in organisms across all three domains of life, where they play vital roles in diverse cellular processes including nucleic acid and protein biosynthesis and biosilica precipitation in diatom frustule formation. The dominant form of free polyamines in seawater is as short-chain aliphatic compounds (e.g., putrescine, spermidine and spermine). They are thought to be mostly derived from the cytoplasm of living cells, where intracellular concentrations can reach mM levels. As free constituents in seawater, however, polyamine concentrations are only found at nM levels. The internal and external concentrations of polyamines are comparable to other low molecular weight components of DON (e.g. DFAA), suggesting similar biogeochemical cycling driven primarily by microbial activity. Recent genomic and metagenomic/ meta-transcriptomic data of marine microbial communities have repeatedly recovered homologs of genes predicted to be involved in bacterial polyamine metabolism. Thus, the limited evidence available strongly suggests that polyamines may be important substrates for heterotrophic microorganisms in the ocean, with implications for the cycling of both nitrogen and carbon. But compared with other components of the DON pool, such as dissolved free amino acids (DFAA), polyamine turnover in marine systems has received minimal attention. In this project, we employed an experimental metatranscriptomic approach to identify and compare the taxonomic composition and functional genes of bacterioplankton that are involved in utilizing putrescine and spermidine in a Southeast US coastal marine system.
Polyamine Metatranscriptomic Study
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