Kiene, R. P. University of South Alabama, rkiene@jaguar1.usouthal.edu
Linn, L. P. University of South Alabama, llinn@mobile.gulf.net

 
ASSIMILATION OF DMSP-SULFUR INTO THE PROTEIN FRACTION OF MARINE BACTERIOPLANKTON.
 
Dissolved DMSP in seawater turns over rapidly and represents a significant source of labile carbon and possibly reduced sulfur for bacterioplankton. Addition of tracer-level 35S-DMSP to seawater or seawater filtrates (< 0.8 um) revealed that the DMSP was taken up very rapidly by bacteria and assimilated into a trichloracetic acid (TCA) insoluble pool. Tests showed that > 75% of the TCA-insoluble 35S material formed from DMSP was solublized by Proteinase K, suggesting it was mostly protein. Consistent with this interpretation, the assimilation of 35S-DMSP into the TCA-insoluble pool was inhibited > 90% by 10 mg/l chloramphenicol, an inhibitor of protein synthesis in prokaryotes. Acid hydrolysis of 35S-DMSP-treated cells, and subsequent HPLC separation of amino acids, revealed that most of the 35S activity was in the form of methionine. Overall, the assimilation of DMSP-sulfur into bacterial proteins accounted for ~50% of the added 35S in tracer addition experiments, therefore this phenomenon represents a major biogeochemical fate of DMSP-sulfur and a major limitation on production of climatically-active dimethylsulfide from DMSP. These findings imply that bacterial growth rates (and hence protein synthesis rates) may strongly influence the fate of DMSP, and further suggest that DMSP is a major source of reduced sulfur for bacterioplankton.
 
Day: Friday, Feb. 5
Time: 12:15 - 12:30pm
Location: Sweeney Center
 
Code: SS37FR1215S