Ronald Kiene | University of South Alabama (original) (raw)

Papers by Ronald Kiene

Applied and Environmental Microbiology

Over half of the bacterioplankton cells in ocean surface waters are capable of carrying out a dem... more Over half of the bacterioplankton cells in ocean surface waters are capable of carrying out a demethylation of the phytoplankton metabolite dimethylsulfoniopropionate (DMSP) that routes the sulfur moiety away from the climatically active gas dimethylsulfide (DMS). In this study, we tracked changes in dmdA, the gene responsible for DMSP demethylation, over the course of an induced phytoplankton bloom in Gulf of Mexico seawater microcosms. Analysis of >91,000 amplicon sequences indicated 578 different dmdA sequence clusters at a conservative clustering criterion of ≥90% nucleotide sequence identity over the 6-day study. The representation of the major clades of dmdA, several of which are linked to specific taxa through genomes of cultured marine bacterioplankton, remained fairly constant. However, the representation of clusters within these major clades shifted significantly in response to the bloom, including two Roseobacter-like clusters and a SAR11-like cluster, and the best cor...

Biogeochemistry of Global Change, 1993

Journal of Chromatography B, 2015

The organic sulfur compound 3-mercaptopropionic acid (3-MPA) is an important thiol intermediate i... more The organic sulfur compound 3-mercaptopropionic acid (3-MPA) is an important thiol intermediate in organic sulfur metabolism in natural environments. It is generated during degradation of sulfur-containing amino acids (e.g. methionine) and from demethylation of dimethylsulfoniopropionate (DMSP). This pathway is an alternative enzymatic process in the DMSP catabolism that routes sulfur away from the climatically-active dimethyl sulfide (DMS). 3-MPA detection and subsequent quantification in different matrices is difficult due to its extreme reactivity. We therefore developed a sensitive method for determination of 3-MPA based on pre-column derivatization with monobromobimane and analysis by high-performance liquid chromatography (HPLC) with fluorescence detection. This methodology was first tested with 3-MPA standards under low (0.005-0.2 mol L −1 ) and high (1-25 mol L −1 ) concentrations. For the optimization of the reaction, CHES and, alternatively, Tris-HCl buffers were evaluated in the derivatization step, with Tris-HCl showing more effective separation of thiol derivatives and a better 3-MPA peak shape. The detection limit was 4.3 nmol L −1 with a 10 L sample injection, and mean recoveries of 3-MPA ranged from 97 to 105% in estuarine waters with different salinities (0.17 and 35.9 ppt). The linearity (r > 0.99) and repeatability of detector response, with intra-and inter-day precision (% CV) of 2.68-7.01% and 4.86-12.5%, respectively, confirmed the reliability of the method. Previous 3-MPA analytical methods required immediate analysis due to unstable derivatives, but in this method we achieved high stability of the derivatized samples when stored at 4 • C, with only a 3-5% loss after more than one year of storage. This method was successfully applied to measure 3-MPA concentrations and rates of 3-MPA production in a variety of intertidal estuarine sediment slurries. Dissolved 3-MPA concentrations in these sediment slurries varied between 2 and 237 mol L −1 and, 3-MPA net fluxes ranged in wet sediments between −3.6 ± 1.7 and 30 ± 5 mol L −1 g −1 h −1 . Thus, the application of this optimized methodology showed an efficient performance for measuring 3-MPA in environmental samples, with a straightforward sample derivatization and a simple analysis of stable 3-MPA derivatives.

Marine Chemistry, 2014

Dimethylsulphoxide (DMSO) is a sulphur compound that can result from the oxidation of biogenic di... more Dimethylsulphoxide (DMSO) is a sulphur compound that can result from the oxidation of biogenic dimethylsulphide (DMS) in marine algae and bacteria; with dimethylsulphoniopropionate (DMSP) being the main precursor of DMS. The two most commonly used methods for the analysis of DMSO in seawater and biological samples consist of its chemical reduction to DMS by either titanium trichloride (TiCl 3 ) or sodium borohydride (NaBH 4 ), with subsequent measurement of derived DMS by gas chromatography. Here, these two methods have been compared for the quantitative analysis of DMSO in the zooxanthellate coral Acropora aspera and in two species of marine algae (Ulva intestinalis and Ulva lactuca) using headspace analysis on DMSO-derived DMS. Reduction by NaBH 4 or TiCl 3 in biological samples yielded highly linear calibrations (R 2 ≥ 0.99) and excellent repeatability (RSD = 6.17% and 4.32% for TiCl 3 and NaBH 4 respectively, n = 10). In coral samples, although a strong linear correlation was generally obtained between the two reduction methods (R 2 = 0.8464, p b 0.001, n = 72), the regression slope of 0.6 indicated that DMSO concentrations were either underestimated with NaBH 4 reduction or overestimated with TiCl 3 . Reduction with TiCl 3 yielded lower values than NaBH 4 at DMSO concentrations b0.6 μM, whereas TiCl 3 gave higher values than NaBH 4 when DMSO was N 2 μM. The reasons for these significant differences remain unclear at this stage and we therefore cannot draw conclusions on the preferential suitability of one reducing agent over the other for coral DMSO analysis. In macroalgae samples, significantly lower DMSO concentrations were obtained with NaBH 4 than with TiCl 3 for DMSO concentrations averaging 0.6 μM and 0.8 μM for U. intestinalis and U. lactuca respectively. The difference between reduction methods in the analysis of DMSO across macroalgae and coral samples was interpreted as a difference in taxa or in sample preparation, although this needs to be further investigated. Corals were found to contain more DMSO than macroalgae with similar DMSP concentrations.

Limnology and Oceanography, 2002

A recently described unicellular chlorophytic alga isolated from meromictic Mono Lake, California... more A recently described unicellular chlorophytic alga isolated from meromictic Mono Lake, California, occupies a niche that spans two environments: the upper oxic mixolimnion and the deeper anoxic and highly reducing monimolimnion. This organism, Picocystis sp. strain ML, accounts for nearly 25% of the primary production during the winter bloom and more than 50% at other times of the year. In incubations, it is heavily grazed by the brine shrimp, Artemia monica. We assessed growth and photosynthetic parameters over broad ranges of irradiance, salinity, and pH and under oxic and anoxic conditions. Picocystis appears to be particularly adapted to low irradiance; we observed an order of magnitude increase in the cellular pigment concentrations, as well as marked increases in cellspecific photosynthetic parameters for cells acclimated to low-growth irradiance. Growth rates of 0.3-1.5 d Ϫ1 were observed over a salinity range of 0-260‰ and a pH range of 4-12, with maximal growth at ϳ50 mol photons m Ϫ2 s Ϫ1 , 40‰, and pH 6-10. Growth and oxygenic photosynthesis were observed under anoxic conditions at rates comparable to those measured under oxic conditions. The ability of the organism to acclimate and grow under such a broad range of environmental conditions makes it an important component of the Mono Lake ecosystem and likely contributes to its dominance of the monimolimnion/mixolimnion interface.

Applied and environmental microbiology, 1987

Anoxic salt marsh sediments were amended with dl-methionine and dimethylsulfoniopropionate (DMSP)... more Anoxic salt marsh sediments were amended with dl-methionine and dimethylsulfoniopropionate (DMSP). Microbial metabolism of methionine yielded methane thiol (MSH) as the major volatile organosulfur product, with the formation of lesser amounts of dimethylsulfide (DMS). Biological transformation of DMSP resulted in the rapid release of DMS and only small amounts of MSH. Experiments with microbial inhibitors indicated that production of MSH from methionine was carried out by procaryotic organisms, probably sulfate-reducing bacteria. Methane-producing bacteria did not metabolize methionine. The involvement of specific groups of organisms in DMSP hydrolysis could not be determined with the inhibitors used, because DMSP was hydrolyzed in all samples except those which were autoclaved. Unamended sediment slurries, prepared from Spartina alterniflora sediments, contained significant (1 to 10 muM) concentrations of DMS. Endogenous methylated sulfur compounds and those produced from added met...

Applied and environmental microbiology, 1999

Organic sulfur compounds are present in all aquatic systems, but their use as sources of sulfur f... more Organic sulfur compounds are present in all aquatic systems, but their use as sources of sulfur for bacteria is generally not considered important because of the high sulfate concentrations in natural waters. This study investigated whether dimethylsulfoniopropionate (DMSP), an algal osmolyte that is abundant and rapidly cycled in seawater, is used as a source of sulfur by bacterioplankton. Natural populations of bacterioplankton from subtropical and temperate marine waters rapidly incorporated 15 to 40% of the sulfur from tracer-level additions of [(35)S]DMSP into a macromolecule fraction. Tests with proteinase K and chloramphenicol showed that the sulfur from DMSP was incorporated into proteins, and analysis of protein hydrolysis products by high-pressure liquid chromatography showed that methionine was the major labeled amino acid produced from [(35)S]DMSP. Bacterial strains isolated from coastal seawater and belonging to the alpha-subdivision of the division Proteobacteria incor...

Applied and environmental microbiology, 1994

A bacterium, strain BIS-6, that grew aerobically on dimethylsulfoniopropionate (DMSP) was isolate... more A bacterium, strain BIS-6, that grew aerobically on dimethylsulfoniopropionate (DMSP) was isolated from an intertidal mud sample. Strain BIS-6 quantitatively demethylated DMSP and 3-methiolpropionate to 3-mercaptopropionate. Strain BIS-6 was a versatile methylotroph growing on the osmolytes DMSP and glycine betaine and their methylated degradation products (dimethyl glycine, sarcosine, methylamines, and dimethyl sulfide.

Biogeochemistry of Global Change, 1993

Biogeosciences Discussions, 2010

The production of large amounts of algal biomass for different purposes such as aquaculture or bi... more The production of large amounts of algal biomass for different purposes such as aquaculture or biofuels, may cause impacts on the marine environment. One such impact is the production of radiatively active trace gases and aerosols with climate cooling (dimethyl sulfide DMS and its precursor DMSP) and warming (N2O and CH4) effects. Total and dissolved DMSP, N2O and CH4, together with other environmental variables were monitored daily for 46 days within a massive microalgae monoculture of Nannochloris (Chlorophyceae) in an open pond system. The growth of this green microalgae was stimulated by the addition of N- and P-rich salts, resulting in exponential growth (growth phase) during the first 17 days observed by cell abundance (1 × 106 to 4.4 × 106 cell mL-1) and Chl-a levels (from 1.4 to 96 mg Chl-a m-3) followed by a decrease in both Chl-a and cell abundance (senescence phase). Total DMSP (from 6.3 to 142 mumol m-3), dissolved DMSP i.e. 5.8 to 137 mumol m-3 and N2O (from 8 to 600 mumol m-3) abruptly peaked during the senescence phase, whereas CH4 steadily increased between 2 and 10 mumol m-3 during the growth phase. Different ratios between tracers and Chl-a during both phases reveal different biochemical processes involved in the cycling of these gases and tracers. Our results show that despite the consumption of large quantities of CO2 by the massive algal culture, a minor amount of DMS and huge amounts of greenhouse gases were produced, in particular N2O, which has a greater radiative effect per molecule than CO2. These findings have important implications for biogeochemical studies and for environmental management of aquaculture activities.

Biological and Environmental Chemistry of DMSP and Related Sulfonium Compounds, 1996

... Rik LJ Kwint, Xabier Irigoien and Kees JM Kramer ... GPT) can then be calculated from the dec... more ... Rik LJ Kwint, Xabier Irigoien and Kees JM Kramer ... GPT) can then be calculated from the decrease in gut content (G) according to: Gt = G0 e-gt and GPT = 1/g, where g is the gut clearance rate constant in min-1, Gt is the gut content at each time step in pmol DMSP ind-1. The ...

The ISME Journal, 2015

The &... more 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 cleavage pathway was relatively greater during a high-DMSP-producing dinoflagellate bloom, and expression of the demethylation pathway was greater in the presence of a mixed diatom and dinoflagellate community. 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.The ISME Journal advance online publication, 20 February 2015; doi:10.1038/ismej.2015.23.

Marine Ecology Progress Series, 2014

This study reports on the temporal variations in algal and bacterial metabolism of dissolved dime... more This study reports on the temporal variations in algal and bacterial metabolism of dissolved dimethylsulfoniopropionate (DMSPd) in Arctic ice-covered waters in response to the release of organic matter (OM) from the sea ice and the onset of under-ice phytoplankton growth. Sampling took place between 21 May and 21 June 2012 at a station located in Resolute Passage. A snow and ice melt event was accompanied by an important release of OM and total DMSP from the bottom ice to the water column. This input of OM coincided with increases in DMSPd and DMSPd loss rate constant at the ice-water interface and, 2 days later, with increases in DMSPd and bacterial dimethylsulfide (DMS) yields from DMSPd at 0.5 m under the ice. The different microbial responses suggest that DMSPd-rich brines were released first, followed by the release of sympagic algae due to ice melt. In both cases, the changes in DMSPd metabolism resulted in an increase in gross DMS production from 0.15 to 1.9 nmol l −1 d −1 . The initiation of phytoplankton growth resulted in increases in bacterial abundance, DMSPd loss-rate constant and DMSP-sulfur assimilation. In contrast, DMS yield remained low during the onset of phytoplankton growth, indicating that bacteria used DMSP as a carbon and sulfur source. These results show that ice DMSPd can be rapidly (<1 d) and efficiently (up to 10%) converted into DMS by bacteria once released in surface water during melt events, a process that could contribute to DMS peaks measured at the ice edge.

Journal of Microbiology, 2014

the main precursor of dimethylsulfide (DMS), a gas that influences atmospheric chemistry and pote... more the main precursor of dimethylsulfide (DMS), a gas that influences atmospheric chemistry and potentially the global climate. In nature, bacterial DMSP catabolism can yield different proportions of DMS and methanethiol (MeSH), but relatively little is known about the factors controlling the pathways of bacterial degradation that select between their formation (cleavage vs. demethiolation). In this study, we carried out experiments to evaluate the influence of salinity on the routes of DMSP catabolism in Ruegeria pomeroyi DSS-3. We monitored DMS and MeSH accumulation in cell suspensions grown in a range of salinities (10, 20, 30 ppt) and with different DMSP amendments (0, 50, 500 μM). Significantly higher concentrations of DMS accumulated in low salinity treatments (10 ppt; P < 0.001), in both Marine Basal Medium (MBM) and half-strength Yeast Tryptone Sea Salts (½ YTSS) media. Results showed a 47.1% and 87.5% decrease of DMS accumulation, from salinity 10 to 20 ppt, in MBM and ½ YTSS media, respectively. On the other hand, MeSH showed enhanced accumulations at higher salinities (20, 30 ppt), with a 90.6% increase of MeSH accumulation from the 20 ppt to the 30 ppt salinity treatments. Our results with R. pomeroyi DSS-3 in culture are in agreement with previous results from estuarine sediments and demonstrate that salinity can modulate selection of the DMSP enzymatic degradation routes, with a consequent potential impact on DMS and MeSH liberation into the atmosphere.

Applied and Environmental Microbiology

Over half of the bacterioplankton cells in ocean surface waters are capable of carrying out a dem... more Over half of the bacterioplankton cells in ocean surface waters are capable of carrying out a demethylation of the phytoplankton metabolite dimethylsulfoniopropionate (DMSP) that routes the sulfur moiety away from the climatically active gas dimethylsulfide (DMS). In this study, we tracked changes in dmdA, the gene responsible for DMSP demethylation, over the course of an induced phytoplankton bloom in Gulf of Mexico seawater microcosms. Analysis of >91,000 amplicon sequences indicated 578 different dmdA sequence clusters at a conservative clustering criterion of ≥90% nucleotide sequence identity over the 6-day study. The representation of the major clades of dmdA, several of which are linked to specific taxa through genomes of cultured marine bacterioplankton, remained fairly constant. However, the representation of clusters within these major clades shifted significantly in response to the bloom, including two Roseobacter-like clusters and a SAR11-like cluster, and the best cor...

Biogeochemistry of Global Change, 1993

Journal of Chromatography B, 2015

The organic sulfur compound 3-mercaptopropionic acid (3-MPA) is an important thiol intermediate i... more The organic sulfur compound 3-mercaptopropionic acid (3-MPA) is an important thiol intermediate in organic sulfur metabolism in natural environments. It is generated during degradation of sulfur-containing amino acids (e.g. methionine) and from demethylation of dimethylsulfoniopropionate (DMSP). This pathway is an alternative enzymatic process in the DMSP catabolism that routes sulfur away from the climatically-active dimethyl sulfide (DMS). 3-MPA detection and subsequent quantification in different matrices is difficult due to its extreme reactivity. We therefore developed a sensitive method for determination of 3-MPA based on pre-column derivatization with monobromobimane and analysis by high-performance liquid chromatography (HPLC) with fluorescence detection. This methodology was first tested with 3-MPA standards under low (0.005-0.2 mol L −1 ) and high (1-25 mol L −1 ) concentrations. For the optimization of the reaction, CHES and, alternatively, Tris-HCl buffers were evaluated in the derivatization step, with Tris-HCl showing more effective separation of thiol derivatives and a better 3-MPA peak shape. The detection limit was 4.3 nmol L −1 with a 10 L sample injection, and mean recoveries of 3-MPA ranged from 97 to 105% in estuarine waters with different salinities (0.17 and 35.9 ppt). The linearity (r > 0.99) and repeatability of detector response, with intra-and inter-day precision (% CV) of 2.68-7.01% and 4.86-12.5%, respectively, confirmed the reliability of the method. Previous 3-MPA analytical methods required immediate analysis due to unstable derivatives, but in this method we achieved high stability of the derivatized samples when stored at 4 • C, with only a 3-5% loss after more than one year of storage. This method was successfully applied to measure 3-MPA concentrations and rates of 3-MPA production in a variety of intertidal estuarine sediment slurries. Dissolved 3-MPA concentrations in these sediment slurries varied between 2 and 237 mol L −1 and, 3-MPA net fluxes ranged in wet sediments between −3.6 ± 1.7 and 30 ± 5 mol L −1 g −1 h −1 . Thus, the application of this optimized methodology showed an efficient performance for measuring 3-MPA in environmental samples, with a straightforward sample derivatization and a simple analysis of stable 3-MPA derivatives.

Marine Chemistry, 2014

Dimethylsulphoxide (DMSO) is a sulphur compound that can result from the oxidation of biogenic di... more Dimethylsulphoxide (DMSO) is a sulphur compound that can result from the oxidation of biogenic dimethylsulphide (DMS) in marine algae and bacteria; with dimethylsulphoniopropionate (DMSP) being the main precursor of DMS. The two most commonly used methods for the analysis of DMSO in seawater and biological samples consist of its chemical reduction to DMS by either titanium trichloride (TiCl 3 ) or sodium borohydride (NaBH 4 ), with subsequent measurement of derived DMS by gas chromatography. Here, these two methods have been compared for the quantitative analysis of DMSO in the zooxanthellate coral Acropora aspera and in two species of marine algae (Ulva intestinalis and Ulva lactuca) using headspace analysis on DMSO-derived DMS. Reduction by NaBH 4 or TiCl 3 in biological samples yielded highly linear calibrations (R 2 ≥ 0.99) and excellent repeatability (RSD = 6.17% and 4.32% for TiCl 3 and NaBH 4 respectively, n = 10). In coral samples, although a strong linear correlation was generally obtained between the two reduction methods (R 2 = 0.8464, p b 0.001, n = 72), the regression slope of 0.6 indicated that DMSO concentrations were either underestimated with NaBH 4 reduction or overestimated with TiCl 3 . Reduction with TiCl 3 yielded lower values than NaBH 4 at DMSO concentrations b0.6 μM, whereas TiCl 3 gave higher values than NaBH 4 when DMSO was N 2 μM. The reasons for these significant differences remain unclear at this stage and we therefore cannot draw conclusions on the preferential suitability of one reducing agent over the other for coral DMSO analysis. In macroalgae samples, significantly lower DMSO concentrations were obtained with NaBH 4 than with TiCl 3 for DMSO concentrations averaging 0.6 μM and 0.8 μM for U. intestinalis and U. lactuca respectively. The difference between reduction methods in the analysis of DMSO across macroalgae and coral samples was interpreted as a difference in taxa or in sample preparation, although this needs to be further investigated. Corals were found to contain more DMSO than macroalgae with similar DMSP concentrations.

Limnology and Oceanography, 2002

A recently described unicellular chlorophytic alga isolated from meromictic Mono Lake, California... more A recently described unicellular chlorophytic alga isolated from meromictic Mono Lake, California, occupies a niche that spans two environments: the upper oxic mixolimnion and the deeper anoxic and highly reducing monimolimnion. This organism, Picocystis sp. strain ML, accounts for nearly 25% of the primary production during the winter bloom and more than 50% at other times of the year. In incubations, it is heavily grazed by the brine shrimp, Artemia monica. We assessed growth and photosynthetic parameters over broad ranges of irradiance, salinity, and pH and under oxic and anoxic conditions. Picocystis appears to be particularly adapted to low irradiance; we observed an order of magnitude increase in the cellular pigment concentrations, as well as marked increases in cellspecific photosynthetic parameters for cells acclimated to low-growth irradiance. Growth rates of 0.3-1.5 d Ϫ1 were observed over a salinity range of 0-260‰ and a pH range of 4-12, with maximal growth at ϳ50 mol photons m Ϫ2 s Ϫ1 , 40‰, and pH 6-10. Growth and oxygenic photosynthesis were observed under anoxic conditions at rates comparable to those measured under oxic conditions. The ability of the organism to acclimate and grow under such a broad range of environmental conditions makes it an important component of the Mono Lake ecosystem and likely contributes to its dominance of the monimolimnion/mixolimnion interface.

Applied and environmental microbiology, 1987

Anoxic salt marsh sediments were amended with dl-methionine and dimethylsulfoniopropionate (DMSP)... more Anoxic salt marsh sediments were amended with dl-methionine and dimethylsulfoniopropionate (DMSP). Microbial metabolism of methionine yielded methane thiol (MSH) as the major volatile organosulfur product, with the formation of lesser amounts of dimethylsulfide (DMS). Biological transformation of DMSP resulted in the rapid release of DMS and only small amounts of MSH. Experiments with microbial inhibitors indicated that production of MSH from methionine was carried out by procaryotic organisms, probably sulfate-reducing bacteria. Methane-producing bacteria did not metabolize methionine. The involvement of specific groups of organisms in DMSP hydrolysis could not be determined with the inhibitors used, because DMSP was hydrolyzed in all samples except those which were autoclaved. Unamended sediment slurries, prepared from Spartina alterniflora sediments, contained significant (1 to 10 muM) concentrations of DMS. Endogenous methylated sulfur compounds and those produced from added met...

Applied and environmental microbiology, 1999

Organic sulfur compounds are present in all aquatic systems, but their use as sources of sulfur f... more Organic sulfur compounds are present in all aquatic systems, but their use as sources of sulfur for bacteria is generally not considered important because of the high sulfate concentrations in natural waters. This study investigated whether dimethylsulfoniopropionate (DMSP), an algal osmolyte that is abundant and rapidly cycled in seawater, is used as a source of sulfur by bacterioplankton. Natural populations of bacterioplankton from subtropical and temperate marine waters rapidly incorporated 15 to 40% of the sulfur from tracer-level additions of [(35)S]DMSP into a macromolecule fraction. Tests with proteinase K and chloramphenicol showed that the sulfur from DMSP was incorporated into proteins, and analysis of protein hydrolysis products by high-pressure liquid chromatography showed that methionine was the major labeled amino acid produced from [(35)S]DMSP. Bacterial strains isolated from coastal seawater and belonging to the alpha-subdivision of the division Proteobacteria incor...

Applied and environmental microbiology, 1994

A bacterium, strain BIS-6, that grew aerobically on dimethylsulfoniopropionate (DMSP) was isolate... more A bacterium, strain BIS-6, that grew aerobically on dimethylsulfoniopropionate (DMSP) was isolated from an intertidal mud sample. Strain BIS-6 quantitatively demethylated DMSP and 3-methiolpropionate to 3-mercaptopropionate. Strain BIS-6 was a versatile methylotroph growing on the osmolytes DMSP and glycine betaine and their methylated degradation products (dimethyl glycine, sarcosine, methylamines, and dimethyl sulfide.

Biogeochemistry of Global Change, 1993

Biogeosciences Discussions, 2010

The production of large amounts of algal biomass for different purposes such as aquaculture or bi... more The production of large amounts of algal biomass for different purposes such as aquaculture or biofuels, may cause impacts on the marine environment. One such impact is the production of radiatively active trace gases and aerosols with climate cooling (dimethyl sulfide DMS and its precursor DMSP) and warming (N2O and CH4) effects. Total and dissolved DMSP, N2O and CH4, together with other environmental variables were monitored daily for 46 days within a massive microalgae monoculture of Nannochloris (Chlorophyceae) in an open pond system. The growth of this green microalgae was stimulated by the addition of N- and P-rich salts, resulting in exponential growth (growth phase) during the first 17 days observed by cell abundance (1 × 106 to 4.4 × 106 cell mL-1) and Chl-a levels (from 1.4 to 96 mg Chl-a m-3) followed by a decrease in both Chl-a and cell abundance (senescence phase). Total DMSP (from 6.3 to 142 mumol m-3), dissolved DMSP i.e. 5.8 to 137 mumol m-3 and N2O (from 8 to 600 mumol m-3) abruptly peaked during the senescence phase, whereas CH4 steadily increased between 2 and 10 mumol m-3 during the growth phase. Different ratios between tracers and Chl-a during both phases reveal different biochemical processes involved in the cycling of these gases and tracers. Our results show that despite the consumption of large quantities of CO2 by the massive algal culture, a minor amount of DMS and huge amounts of greenhouse gases were produced, in particular N2O, which has a greater radiative effect per molecule than CO2. These findings have important implications for biogeochemical studies and for environmental management of aquaculture activities.

Biological and Environmental Chemistry of DMSP and Related Sulfonium Compounds, 1996

... Rik LJ Kwint, Xabier Irigoien and Kees JM Kramer ... GPT) can then be calculated from the dec... more ... Rik LJ Kwint, Xabier Irigoien and Kees JM Kramer ... GPT) can then be calculated from the decrease in gut content (G) according to: Gt = G0 e-gt and GPT = 1/g, where g is the gut clearance rate constant in min-1, Gt is the gut content at each time step in pmol DMSP ind-1. The ...

The ISME Journal, 2015

The &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;... more The &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;bacterial switch&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; 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 cleavage pathway was relatively greater during a high-DMSP-producing dinoflagellate bloom, and expression of the demethylation pathway was greater in the presence of a mixed diatom and dinoflagellate community. 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.The ISME Journal advance online publication, 20 February 2015; doi:10.1038/ismej.2015.23.

Marine Ecology Progress Series, 2014

This study reports on the temporal variations in algal and bacterial metabolism of dissolved dime... more This study reports on the temporal variations in algal and bacterial metabolism of dissolved dimethylsulfoniopropionate (DMSPd) in Arctic ice-covered waters in response to the release of organic matter (OM) from the sea ice and the onset of under-ice phytoplankton growth. Sampling took place between 21 May and 21 June 2012 at a station located in Resolute Passage. A snow and ice melt event was accompanied by an important release of OM and total DMSP from the bottom ice to the water column. This input of OM coincided with increases in DMSPd and DMSPd loss rate constant at the ice-water interface and, 2 days later, with increases in DMSPd and bacterial dimethylsulfide (DMS) yields from DMSPd at 0.5 m under the ice. The different microbial responses suggest that DMSPd-rich brines were released first, followed by the release of sympagic algae due to ice melt. In both cases, the changes in DMSPd metabolism resulted in an increase in gross DMS production from 0.15 to 1.9 nmol l −1 d −1 . The initiation of phytoplankton growth resulted in increases in bacterial abundance, DMSPd loss-rate constant and DMSP-sulfur assimilation. In contrast, DMS yield remained low during the onset of phytoplankton growth, indicating that bacteria used DMSP as a carbon and sulfur source. These results show that ice DMSPd can be rapidly (<1 d) and efficiently (up to 10%) converted into DMS by bacteria once released in surface water during melt events, a process that could contribute to DMS peaks measured at the ice edge.

Journal of Microbiology, 2014

the main precursor of dimethylsulfide (DMS), a gas that influences atmospheric chemistry and pote... more the main precursor of dimethylsulfide (DMS), a gas that influences atmospheric chemistry and potentially the global climate. In nature, bacterial DMSP catabolism can yield different proportions of DMS and methanethiol (MeSH), but relatively little is known about the factors controlling the pathways of bacterial degradation that select between their formation (cleavage vs. demethiolation). In this study, we carried out experiments to evaluate the influence of salinity on the routes of DMSP catabolism in Ruegeria pomeroyi DSS-3. We monitored DMS and MeSH accumulation in cell suspensions grown in a range of salinities (10, 20, 30 ppt) and with different DMSP amendments (0, 50, 500 μM). Significantly higher concentrations of DMS accumulated in low salinity treatments (10 ppt; P < 0.001), in both Marine Basal Medium (MBM) and half-strength Yeast Tryptone Sea Salts (½ YTSS) media. Results showed a 47.1% and 87.5% decrease of DMS accumulation, from salinity 10 to 20 ppt, in MBM and ½ YTSS media, respectively. On the other hand, MeSH showed enhanced accumulations at higher salinities (20, 30 ppt), with a 90.6% increase of MeSH accumulation from the 20 ppt to the 30 ppt salinity treatments. Our results with R. pomeroyi DSS-3 in culture are in agreement with previous results from estuarine sediments and demonstrate that salinity can modulate selection of the DMSP enzymatic degradation routes, with a consequent potential impact on DMS and MeSH liberation into the atmosphere.