DOC incorporation by Sargasso Sea bacterioplankton
Sargasso Sea Bacterioplankton Community
We analyzed gene expression profiles of a prokaryotic community from surface waters of the western North Atlantic Ocean (BATS station). Samples were enriched with the organic sulfur compound DMSP (25 nM, final concentration) and compared with a no-addition control. An average of 270,675 unique reads were obtained per treatment after using 454 pyrosequencing technology to sequence the extracted and amplified messenger RNA (mRNA). Approximately 41% of the reads were assigned a protein function based on BLAST analysis against the NCBI RefSeq database. Transcripts in the DMSP treatment had more frequent hits to Gammaproteobacteria, suggesting that this group might be the first to react when DMSP becomes available. DMSP enrichment resulted in relatively higher expression of genes required for growth and energy generation. Separate specific enrichments with various products of DMSP degradation were also performed along with biogeochemical rate measurements (DMSP uptake, consumption and assimilation). Using bioinformatic tools to identify transcripts from known DMSP-related genes, we generated ecosystem-specific primers for several DMSP degradation steps. Rate measurements were less sensitive in tracking subtle changes in sulfur cycling than direct tracking of gene expression.