Biosynthesis of dimethylsulfide and dimethylpropiothetin by Hymenomonas carterae in relation to sulfur source and salinity variations

Abstract

The marine coccolithophorid phytoplankton species Hymenomonas carterae (class Prymnesiophyceae) produces both dimethylpropiothetin (DMPT) and dimethylsulfide (DMS) in axenic cultures. The rate of DMS production is closely regulated by the cell; it remains independent of environmental sulfate concentration down to levels of 2.5% of the seawater value. Below this sulfate level, DMS production decreases with decreasing sulfate concentration, but significant amounts of DMS are released even under conditions of sulfate-limited growth. Hymenomonas carterae can grow on sulfite, thiosulfate, and cysteine as sulfur sources, but not on methionine. The rate of DMS output is similar for the different sulfur sources.Both the intracellular concentration of DMPT and the rate of output of DMS by H. carterae increase with increasing salinity of the medium. This increase is observed when either salt or sucrose is used to control the osmolarity of the growth medium. Variations in DMPT levels and DMS output were observed within hours after transferring cells to a medium of different osmotic pressure. The intracellular DMPT concentration is of the order of 0.3 mole per liter and contributes significantly to the osmotic pressure in the cell. These results suggest that DMPT plays an important role in osmoregulation by H. carterae.

Compatible solutes in three marine intertidal microphytobenthic Wadden Sea diatoms exposed to different salinities

“…On the other hand, it is quite possible that lower concentrations of this compound were not detected due to the method used. However, when cultured for a prolonged period of time, DMSP has been found to increase with salinity in several micro-and macroalgal species (Vairavamurthy et al, 1985;Dickson & Kirst, 1986, 1987a, 1987bKarsten et al, 1992). Due to its usually high intracellular concentrations in the present investigation, DMSP may thus be considered as a constitutive compatible solute, but not as an osmoticum in the strict sense of being responsible for osmotic balance (Reed, 1984).…”

Annual cycle of dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) related to phytoplankton succession in the Southern North Sea

“…Similarly, the biogenic production of DMSO is specific and generally correlated to DMSP production (Hatton and Wilson, 2007). There are different sources of specific variability in DMSP and DMSO production including growth stage, salinity, temperature, nutrient limitation and light related to several potential physiological functions of these molecules as osmoregulator (Vairavamurthy et al, 1985), cryoprotectant (Kirst et al, 1991), antioxidant (Sunda et al, 2002), methyl donor , grazing deterrent (Wolfe et al, 1997) and overflow mechanism in nitrogen-limiting conditions (Stefels, 2000). DMSP is also a source of carbon (C) and S for heterotrophic organisms (Kiene and Linn, 2000a) and acts as a chemical cue for higher trophic level organisms (Steinke et al, 2002).…”

Distribution and turnover of dissolved DMSP and its relationship with bacterial production and dimethylsulfide in the Gulf of Mexico

“…This conclusion must be viewed with some caution because temporal and spatial differences in the conversion efficiency of DMSP into DMS (see Ledyard and Dacey 1996;van Duyl et al 1998), and other factors such as the bacterial community structure (González et al 1999), and rates of biological consumption, airsea exchange and photochemical destruction of DMS (Kieber et al 1996), would also affect the net DMS accumulations and steady state concentrations in the sea. Additionally, direct release from phytoplankton (Vairavamurthy et al 1985), phytoplankton lyase activity (Stefels et al 1995) and release during grazing or viral lysis (Dacey and Wakeham 1986;Wolfe and Steinke 1996;Malin et al 1998) should be also be considered as potential mechanisms for DMS formation, in addition to bacterial conversion of DMSPd.…”