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Appl. Environ. Microbiol., Aug 1997, 3182-3188, Vol 63, No. 8
DC Yoch, JH Ansede and KS Rabinowitz
The kinetics of dimethylsulfoniopropionate (DMSP) uptake and
dimethylsulfide (DMS) production from DMSP in two bacterial species,
Alcaligenes sp. strain M3A, an isolate from estuarine surface sediments,
and Pseudomonas doudoroffii, from seawater, were investigated. In
Alcaligenes cells induced for DMSP lyase (DL) activity, DMS production
occurred without DMSP uptake. In DL-induced suspensions of P. doudoroffii,
uptake of DMSP preceded the production of DMS, indicating an intracellular
location of DL; intracellular DMSP levels reached ca. 7 mM. DMSP uptake
rates in noninduced cells showed saturation at three concentrations
(K(inft) [transport] values, 3.4, 127, and 500 (mu)M). In DL-induced cells
of P. doudoroffii, DMSP uptake rates increased ca. threefold (V(infmax),
0.022 versus 0.065 (mu)mol of DMSP taken up min(sup-1) mg of cell
protein(sup-1)), suggesting that the uptake binding proteins were
inducible. DMSP uptake and DL activity in P. doudoroffii were both
inhibited by CN(sup-), 2,4-dinitrophenol, and membrane-impermeable
thiol-binding reagents, further indicating active uptake of DMSP by cell
surface components. The respiratory inhibitors had limited or no effect on
DL activity by the Alcaligenes sp. Of the structural analogs of DMSP tested
for their effect on DMSP metabolism, glycine betaine (GBT), but not
methyl-3-mercaptopropionic acid (MMPA), inhibited DMSP uptake by P.
doudoroffii, suggesting that GBT shares a binding protein with DMSP and
that MMPA is taken up at a separate site. Two models of DMSP uptake,
induction, and DL location found in marine bacteria are presented.
Copyright © 1997, American Society for Microbiology
Evidence for Intracellular and Extracellular Dimethylsulfoniopropionate (DMSP) Lyases and DMSP Uptake Sites in Two Species of Marine Bacteria
Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208
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