Sulfur cycle in the typical meadow Calamagrostis angustifolia wetland ecosystem in the Sanjiang Plain,Northeast China

The sulfur cycle and its compartmental distribution within an atmosphere-plant-soil system was studied using a compartment model in the typical meadow Calamagrostis angustifolia wetland in the Sanjiang Plain Northeast China. The results showed that in the typical meadow C. angustifolia wetland ecosystem, soil was the main storage compartment and current hinge of sulfur in which 98.4% sulfur was accumulated, while only 1.6% sulfur was accumulated in the plant compartment. In the plant subsystem, roots and litters were the main storage compartment of sulfur and they remained 83.5% of the total plant sulfur. The calculations of sulfur turnover through the compartments of the typical meadow C. angustifolia wetland ecosystem demonstrated that the above-ground component took up 0.99 gS/m^2 from the root, of which 0.16 gS/m^2 was translocated to the roots and 0.83 gS/m^2 to the litter. The roots took in 1.05 gS/m^2 from the soil, subsequent translocation back to the soil accounted for 1.31 gS/m^2, while there was 1.84 gS/m^2 in the litter and the net transfer of sulfur to the soil was more than 0.44 gS/（m^2·a）. The emission of H2S from the typical meadow C. angustifolia wetland ecosystem to the atmosphere was 1.83 mgS/（m^2·a）, while carbonyl sulfide （COS） was absorbed by the typical meadow C. angustifolia wetland ecosystem from the atmosphere at the rate of 1.76 mgS/（m^2·a）. The input of sulfur by the rainfall to the ecosystem was 4.85 mgS/m^2 during the growing season. The difference between input and output was 4.78 mgS/m^2, which indicated that sulfur was accumulated in the ecosystem and may cause wetland acidify in the future.

Sulfur cycle as an nitrate in a electron mediator between carbon and constructed wetland microcosm

A constructed wetland microcosm was employed to investigate the sulfur cycle-mediated electron transfer between carbon and nitrate.Sulfate accepted electrons from organics at the average rate of 0.84 mol/(m3·d)through sulfate reduction,which accounted for 20.0%of the electron input rate.The remainder of the electrons derived from organics were accepted by dissolved oxygen(2.6%),nitrate(26.8%),and iron(III)(39.9%).The sulfide produced from sulfate reduction was transformed into acidvolatile sulfide,pyrite,and elemental sulfur,which were deposited in the substratum,storing electrons in the microcosm at the average rate of 0.52 mol/(m3·d).In the presence of nitrate,the acid-volatile and elemental sulfur were oxidized to sulfate,donating electrons at the average rate of 0.14 mol/(m3•d)and driving autotrophic denitrification at the average rate of 0.30 g N/(m3·d).The overall electron transfer efficiency of the sulfur cycle for autotrophic denitrification was 15.3%.A mass balance assessment indicated that approximately 50%of the input sulfur was discharged from the microcosm,and the remainder was removed through deposition(49%)and plant uptake(1%).Dominant sulfatereducing(i.e.,Desulfovirga,Desulforhopalus,Desulfatitalea,and Desulfatirhabdium)and sulfuroxidizing bacteria(i.e.,Thiohalobacter,Thiobacillus,Sulfuritalea,and Sulfurisoma),which jointly flilfilled a sustainable sulfur cycle,were identified.These results improved understanding of electron transfers among carbon,nitrogen,and sulfur cycles in constructed wetlands,and are of engineering significance.

Microbial Processes in Stratified Lake Doroninskoe(Transbaikal Region)

In recent decades,meromictic ponds attract the attention of researchers in different directions,because here the character of the physical,chemical and biological processes differ from those of typical mixing waters(Kuznetsov,1970;Hutchinson,1969).In Transbaikalia widely distributed soda and salt lakes with different salinity.Notable among them is Lake Doroninskoye,which has a pronounced stratification for a

Effects of silver nanoparticle size,concentration and coating on soil quality as indicated by arylsulfatase and sulfite oxidase activities

Recently, the nanotechnology industry has seen a growing interest in integrating silver nanoparticles(AgNPs) into agricultural products, which increases soil exposure to these particles. This demands an investigation into the effect of AgNPs on soil health. Changes in soil enzyme activities upon exposure to AgNPs can serve as early indicators of any adverse effects that these particles may have on soil quality. This study aimed to determine the effects of AgNP size, concentration, coating, and exposure time on the activities of two sulfur cycle enzymes, arylsulfatase and sulfite oxidase. To investigate the sensitivity of soil enzyme activity to AgNP contamination, silt loam soil samples were treated with 30, 80, and 200 nm-sized AgNPs coated with citrate, lipoic acid,and polyvinylpyrrolidone at 1, 10, and 100 mg Ag kgsoil, with the changes in enzyme activities monitored at 3 h, 3 d, and 30 d after treatment. For comparison, the effects of silver(Ag) ions on the enzyme activities were studied under similar treatment conditions. For most of the concentrations tested, the inhibitory effects of AgNPs on different enzymes differed, with a much stronger effect on sulfite oxidase activity than on arylsulfatase activity. The AgNP concentration and exposure time played much important roles than coating type and particle size in the effects of AgNPs on soil enzyme activities.

Mechanistic insights into the key marine dimethylsulfoniopropionate synthesis enzyme DsyB/DSYB

Marine algae and bacteria produce approximately eight billion tonnes of the organosulfur molecule dimethylsulfoniopropionate(DMSP)in Earth's surface oceans annually.DMSP is an antistress compound and,once released into the environment,a major nutrient,signaling molecule,and source of climate-active gases.The methionine transamination pathway for DMSP synthesis is used by most known DMSP-producing algae and bacteria.The S-directed S-adenosylmethionine(SAM)-dependent 4-methylthio-2-hydroxybutyrate(MTHB)S-methyltransferase,encoded by the dsyB/DSYB gene,is the key enzyme of this pathway,generating S-adenosylhomocysteine(SAH)and 4-dimethylsulfonio-2-hydroxybutyrate(DMSHB).DsyB/DSYB,present in most haptophyte and dinoflagellate algae with the highest known intracellular DMSP concentrations,is shown to be far more abundant and transcribed in marine environments than any other known S-methyltransferase gene in DMSP synthesis pathways.Furthermore,we demonstrate in vitro activity of the bacterial DsyB enzyme from Nisaea denitrificans and provide its crystal structure in complex with SAM and SAH-MTHB,which together provide the first important mechanistic insights into a DMSP synthesis enzyme.Structural and mutational analyses imply that DsyB adopts a proximity and desolvation mechanism for the methyl transfer reaction.Sequence analysis suggests that this mechanism may be common to all bacterial DsyB enzymes and also,importantly,eukaryotic DSYB enzymes from e.g.,algae that are the major DMSP producers in Earth's surface oceans.