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ISME J. 2015 Jul;9(7):1677-86. doi: 10.1038/ismej.2015.23. Epub 2015 Feb 20.

Single-taxon field measurements of bacterial gene regulation controlling DMSP fate.

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Department of Microbiology, University of Georgia, Athens, GA, USA.
Department of Ocean Sciences, University of California, Santa Cruz, CA, USA.
Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA.
Department of Marine Sciences, University of Georgia, Athens, GA, USA.
1] Department of Marine Sciences, University of South Alabama, Mobile, AL, USA [2] Dauphin Island Sea Lab, Dauphin Island, AL, USA.


The 'bacterial switch' is a proposed regulatory point in the global sulfur cycle that routes dimethylsulfoniopropionate (DMSP) to two fundamentally different fates in seawater through genes encoding either the cleavage or demethylation pathway, and affects the flux of volatile sulfur from ocean surface waters to the atmosphere. Yet which ecological or physiological factors might control the bacterial switch remains a topic of considerable debate. Here we report the first field observations of dynamic changes in expression of DMSP pathway genes by a single marine bacterial species in its natural environment. Detection of taxon-specific gene expression in Roseobacter species HTCC2255 during a month-long deployment of an autonomous ocean sensor in Monterey Bay, CA captured in situ regulation of the first gene in each DMSP pathway (dddP and dmdA) that corresponded with shifts in the taxonomy of the phytoplankton community. Expression of the demethylation pathway was relatively greater during a high-DMSP-producing dinoflagellate bloom, and expression of the cleavage pathway was greater in the presence of a mixed diatom and dinoflagellate community [corrected].These field data fit the prevailing hypothesis for bacterial DMSP gene regulation based on bacterial sulfur demand, but also suggest a modification involving oxidative stress response, evidenced as upregulation of catalase via katG, when DMSP is demethylated.

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