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1.
Photosynthetic activity in carbonate‐rich benthic microbial mats located in saline, alkaline lakes on the Cariboo Plateau, B.C. resulted in pCO 2 below equilibrium and δ 13C DIC values up to +6.0‰ above predicted carbon dioxide (CO 2) equilibrium values, representing a biosignature of photosynthesis. Mat‐associated δ 13C carb values ranged from ~4 to 8‰ within any individual lake, with observations of both enrichments (up to 3.8‰) and depletions (up to 11.6‰) relative to the concurrent dissolved inorganic carbon (DIC). Seasonal and annual variations in δ 13C values reflected the balance between photosynthetic 13C‐enrichment and heterotrophic inputs of 13C‐depleted DIC. Mat microelectrode profiles identified oxic zones where δ 13C carb was within 0.2‰ of surface DIC overlying anoxic zones associated with sulphate reduction where δ 13C carb was depleted by up to 5‰ relative to surface DIC reflecting inputs of 13C‐depleted DIC. δ 13C values of sulphate reducing bacteria biomarker phospholipid fatty acids (PLFA) were depleted relative to the bulk organic matter by ~4‰, consistent with heterotrophic synthesis, while the majority of PLFA had larger offsets consistent with autotrophy. Mean δ 13C org values ranged from ?18.7 ± 0.1 to ?25.3 ± 1.0‰ with mean Δ 13C inorg‐org values ranging from 21.1 to 24.2‰, consistent with non‐CO 2‐limited photosynthesis, suggesting that Precambrian δ 13C org values of ~?26‰ do not necessitate higher atmospheric CO 2 concentrations. Rather, it is likely that the high DIC and carbonate content of these systems provide a non‐limiting carbon source allowing for expression of large photosynthetic offsets, in contrast to the smaller offsets observed in saline, organic‐rich and hot spring microbial mats. 相似文献
2.
Knowledge on microbial community composition and ecology in highly mineralized (TDS up to 71?g l ?1), cold waters (T?<?12?°C) from the zones of restricted water exchange is scarce. Therefore, the aim of our study was to reveal how the particular physicochemical water conditions of these zones affect the community composition. The community members, which could be involved in the sulfur cycling were of particular interest since they may strongly influence wells operation. The pristine, mineral waters of North Poland were extracted from boreholes reaching Cenozoic, Jurassic, and Triassic aquifers at the depth of 46–1248?m below ground surface. Both culture-dependent (culturing on R2A medium) and culture-independent techniques (microscopic methods and high-throughput 16S rDNA amplicon sequencing) were applied. The bacterial communities were characterized by low complexity and strongly varied across the sampling locations. Bacteria potentially involved in the sulfur cycle (sulfate reduction) were common in all mineral waters and were dominant (especially Desulfovibrio) in the deepest waters. The most important geochemical drivers of the observed microbial community composition were TDS including Cl ?, Na +, Mg 2+, and NO 3?. Bacterial isolates belonged mostly to the genus Bacillus. Sequences assigned to Archaea ( Methanobacterium) were detected only in the deepest borehole water. 相似文献
3.
The hydrothermal fluid chemistry at El Tatio Geyser Field (ETGF) in northern Chile suggests that biogenic CO 2–CH 4 cycling may play an important role in water chemistry, and relatively low sulfate (0.6–1 mM) and high molecular hydrogen (H 2) concentrations (67–363 nM) suggest that methanogenic Archaea are present in ETGF microbial mats. In this study, δ 13C analysis of dissolved inorganic carbon and methane was not indicative of biogenic methane production (δ 13C CH4 values ranging from ?15‰ to ?5.3‰); however, methanogenic Archaea were successfully cultured from each of the hydrothermal sites sampled. Sanger sequencing using universal Archaea primers identified putative methanogenic orders with varying metabolic capabilities, including Methanobacteriales, Methanomicrobiales and Methanosarcinales. 相似文献
4.
Alkaline hydrolysis and subcritical water degradation were investigated as ex-situ remediation processes to treat explosive-contaminated soils from military training sites in South Korea. The addition of NaOH solution to the contaminated soils resulted in rapid degradation of the explosives. The degradation of explosives via alkaline hydrolysis was greatly enhanced at pH ≥12. Estimated pseudo-first-order rate constants for the alkaline hydrolysis of 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in contaminated soil at pH 13 were (9.6?±?0.1)×10 ?2, (2.2?±?0.1)×10 ?1, and (1.7?±?0.2)×10 ?2 min ?1, respectively. In the case of subcritical water degradation, the three explosives were completely removed at 200–300°C due to oxidation at high temperatures and pressures. The degradation rate increased as temperature increased. The pseudo-first-order rate constants for DNT, TNT, and RDX at 300°C were (9.4?±?0.8)×10 ?2, (22.8?±?0.3)×10 ?2, and (16.4?±?1.0)×10 ?2, respectively. When the soil-to-water ratio was more than 1:5, the extent of alkaline hydrolysis and subcritical water degradation was significantly inhibited. 相似文献
5.
The molecular and isotopic compositions of lipid biomarkers from cultured filamentous cyanobacteria ( Phormidium, also known as Leptolyngbya) have been used to investigate the community and trophic structure of photosynthetic mats from alkaline hot springs of the Lower Geyser Basin at Yellowstone National Park. We studied a shallow‐water coniform mat from Octopus Spring (OS) and a submerged, tufted mat from Fountain Paint Pots (FPP) and found that 2‐methylhopanepolyols and mid‐chain branched methylalkanes were diagnostic for cyanobacteria, whereas abundant wax esters were representative of the green non‐sulphur bacterial population. The biomarker composition of cultured Phormidium‐isolates varied, but was generally representative of the bulk mat composition. The carbon isotopic fractionation for biomass relative to dissolved inorganic carbon (DIC; ? CO2) for cultures grown with 1% CO 2 ranged from 21.4 to 26.1 and was attenuated by diffusion limitation associated with filament aggregation (i.e. cell clumping). Isotopic differences between biomass and lipid biomarkers, and between lipid classes, depended on the cyanobacterial strain, but was positively correlated with overall fractionation. Acetogenic lipids (alkanes and fatty acids) were generally more depleted than isoprenoids (phytol and hopanoids). The δ 13C TOC for OS and FPP mats were somewhat heavier than for cultures (?16.9 and ?23.6, respectively), which presumably reflects the lower availability of DIC in the natural environment. The isotopic dispersions among cyanobacterial biomarkers, biomass and DIC reflected those established for culture experiments. The 7‐methyl‐ and 7,11‐dimethylheptadecanes were from 9 to 11 depleted relative to the bulk organic carbon, whereas 2‐methylhopanols derived from the oxidation‐reduction of bacteriohopanepolyol were enriched relative to branched alkanes by approximately 5–7. These isotopic relationships survived with depth and indicated that the relatively heavy isotopic composition of the OS mat resulted from diffusion limitation. This study supports the suggestion that culture studies can establish valid isotopic relationships for interpretation of trophic structure in modern and ancient microbial ecosystems. 相似文献
6.
Anoxic sediments from Rotsee (Switzerland) were analyzed for the presence and diversity of methanogens by using molecular tools and for methanogenic activity by using radiotracer techniques, in addition to the measurement of chemical profiles. After PCR-assisted sequence retrieval of the 16S rRNA genes (16S rDNA) from the anoxic sediment of Rotsee, cloning, and sequencing, a phylogenetic analysis identified two clusters of sequences and four separated clones. The sequences in cluster 1 grouped with those of Methanosaeta spp., whereas the sequences in cluster 2 comprised the methanogenic endosymbiont of Plagiopyla nasuta. Discriminative oligonucleotide probes were constructed against both clusters and two of the separated clones. These probes were used subsequently for the analysis of indigenous methanogens in a core of the sediment, in addition to domain-specific probes against members of the domains Bacteria and Archaea and the fluorescent stain 4', 6-diamidino-2-phenylindole (DAPI), by fluorescent in situ hybridization. After DAPI staining, the highest microbial density was obtained in the upper sediment layer; this density decreased with depth from (1.01 +/- 0.25) x 10(10) to (2.62 +/- 0.58) x 10(10) cells per g of sediment (dry weight). This zone corresponded to that of highest metabolic activity, as indicated by the ammonia, alkalinity, and pH profiles, whereas the methane profile was constant. Probes Eub338 and Arch915 detected on average 16 and 6% of the DAPI-stained cells as members of the domains Bacteria and Archaea, respectively. Probe Rotcl1 identified on average 4% of the DAPI-stained cells as Methanosaeta spp., which were present throughout the whole core. In contrast, probe Rotcl2 identified only 0.7% of the DAPI-stained cells as relatives of the methanogenic endosymbiont of P. nasuta, which was present exclusively in the upper 2 cm of the sediment. Probes Rotp13 and Rotp17 did not detect any cells. The spatial distribution of the two methanogenic populations corresponded well to the methane production rates determined by incubation with either [14C]acetate or [14C]bicarbonate. Methanogenesis from acetate accounted for almost all of the total methane production, which concurs with the predominance of acetoclastic Methanosaeta spp. that represented on average 91% of the archaeal population. Significant hydrogenotrophic methanogenesis was found only in the organically enriched upper 2 cm of the sediment, where the probably hydrogenotrophic relatives of the methanogenic endosymbiont of P. nasuta, accounting on average for 7% of the archaeal population, were also detected. 相似文献
7.
The amounts, sources and relative ages of inorganic and organic carbon pools were assessed in eight headwater streams draining watersheds dominated by either forest, pasture, cropland or urban development in the lower Chesapeake Bay region (Virginia, USA). Streams were sampled at baseflow conditions six different times over 1 year. The sources and ages of the carbon pools were characterized by isotopic (δ 13C and ? 14C) analyses and excitation emission matrix fluorescence with parallel factor analysis (EEM–PARAFAC). The findings from this study showed that human land use may alter aquatic carbon cycling in three primary ways. First, human land use affects the sources and ages of DIC by controlling different rates of weathering and erosion. Relative to dissolved inorganic carbon (DIC) in forested streams which originated primarily from respiration of young, 14C-enriched organic matter (OM; δ 13C = ?22.2 ± 3 ‰; ? 14C = 69 ± 14 ‰), DIC in urbanized streams was influenced more by sedimentary carbonate weathering (δ 13C = ?12.4 ± 1 ‰; ? 14C = ?270 ± 37 ‰) and one of pasture streams showed a greater influence from young soil carbonates (δ 13C = ?5.7 ± 2.5 ‰; ? 14C = 69 ‰). Second, human land use alters the proportions of terrestrial versus autochthonous/microbial sources of stream water OM. Fluorescence properties of dissolved OM (DOM) and the C:N of particulate OM (POM) suggested that streams draining human-altered watersheds contained greater relative contributions of DOM and POM from autochthonous/microbial sources than forested streams. Third, human land uses can mobilize geologically aged inorganic carbon and enable its participation in contemporary carbon cycling. Aged DOM (? 14C = ?248 to ?202 ‰, equivalent 14C ages of 1,811–2,284 years BP) and POM (? 14C = ?90 to ?88 ‰, 14C ages of 669–887 years BP) were observed exclusively in urbanized streams, presumably a result of autotrophic fixation of aged DIC (?297 to ?244 ‰, 14C age = 2,251–2,833 years BP) from sedimentary shell dissolution and perhaps also watershed export of fossil fuel carbon. This study demonstrates that human land use may have significant impacts on the amounts, sources, ages and cycling of carbon in headwater streams and their associated watersheds. 相似文献
8.
Synechococcus R-2 (PCC 1942) actively accumulates sulphate in the light and dark. Intracellular sulphate was 1.35 ± 0.23 mol m ?3 (light) and 0.894 ± 0.152 mol m ?3 (dark) under control conditions (BG-11 media: pH o, 7.5; [SO 42?] o, 0.304 mol m ?3). The sulphate transporter is different from that found in higher plants: it appears to be an ATP-driven pump transporting one SO 42?/ATP [ΔμSO 42?i,o=+ 27.7 ± 0.24 kJ mol ?1 (light) and + 24 ± 0.34 kj mol ?1 (dark)]. The rate of metabolism of SO 42?at pH o, 7.5 was 150 ± 28 pmol m ?2 s ?1 (n = 185) in the light but only 12.8 ± 3.6 pmol m ?2 s ?1 (n = 61) in the dark. Light-driven sulphate uptake is partially inhibited by DCMU and chloramphenicol. Sulphate uptake is not linked to potassium, proton, sodium or chloride transport. The alga has a constitutive over-capacity for sulphate uptake [light ( n= 105): Km= 0.3 ± 0.1 mmol m ?3, Vmax, = 1.8 ± 0.6 nmol m ?2 s ?1; dark ( n= 56): Km= 1.4 ± 0.4 mmol m ?3, Vmax= 41 ± 22 pmol m ?2 s ?1]. Sulphite (SO 32?) was a competitive inhibitor of sulphate uptake. Selenate (SeO 42?) was an uncompetitive inhibitor. 相似文献
9.
A computerized oxygen electrode Astern was used to make rapid and accurate measurements of photosynthetic light and dissolved inorganic carbon (DIC) response cures with a macroalga. Ulva rotundata Blid. was grown in an outdoor, continuous flow system in seawater under sunlight or 9% of sunlight at Beaufort, North Carolina. The light compensation points in the shade- and sun-grown plants, measured in seawater, were at photon flux densities (PFDs) of 16 and 27 μmol. Photons·m ?2·s ?1, respectively but the quantum yield of O 2 evolution was not significantly different. Rates of photosynthesis in seawater per unit area of thallus under saturating light and rates of dark respiration were about 1.5-fold higher in sun- than in shade-grown plants. The concentration of DIC in seawater (approximately 2 mM) limited photosynthesis at absorbed PFDs above 60–70 μmol photons·m ?2·s ?1 Addition of 20 mM inorganic carbon had no effect on quantum yield but caused about a 1.5-fold increase in the light-saturated photosynthetic rate in both shade- and sun-grown Ulva. The effect of DIC supplementation was greatest in plants grown in October and least in plants grown in June. The light- and DIC-saturated rate of photosynthesis in seawater was similar to the maximum rate obtained by exposing Ulva to 10% CO 2, in the gas phase. The carbon isotope values (δ 13C, reflecting the 13C/ 12C ratio compared to a standard) of Ulva grown in the same seawater supply were dependent on light and agitation. Samples from Beaufort Inlet were more negative (δ 13C value, ?20.03‰) than those grown in bright light with agitation (δ 13C value, ?17.78‰ outdoors; ?17.23‰ indoors), which may indicate DIC supply limited carbon uptake in seawater. 相似文献
10.
Estimates of carbon leaching losses from different land use systems are few and their contribution to the net ecosystem carbon balance is uncertain. We investigated leaching of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and dissolved methane (CH 4), at forests, grasslands, and croplands across Europe. Biogenic contributions to DIC were estimated by means of its δ13C signature. Leaching of biogenic DIC was 8.3±4.9 g m ?2 yr ?1 for forests, 24.1±7.2 g m ?2 yr ?1 for grasslands, and 14.6±4.8 g m ?2 yr ?1 for croplands. DOC leaching equalled 3.5±1.3 g m ?2 yr ?1 for forests, 5.3±2.0 g m ?2 yr ?1 for grasslands, and 4.1±1.3 g m ?2 yr ?1 for croplands. The average flux of total biogenic carbon across land use systems was 19.4±4.0 g C m ?2 yr ?1. Production of DOC in topsoils was positively related to their C/N ratio and DOC retention in subsoils was inversely related to the ratio of organic carbon to iron plus aluminium (hydr)oxides. Partial pressures of CO 2 in soil air and soil pH determined DIC concentrations and fluxes, but soil solutions were often supersaturated with DIC relative to soil air CO 2. Leaching losses of biogenic carbon (DOC plus biogenic DIC) from grasslands equalled 5–98% (median: 22%) of net ecosystem exchange (NEE) plus carbon inputs with fertilization minus carbon removal with harvest. Carbon leaching increased the net losses from cropland soils by 24–105% (median: 25%). For the majority of forest sites, leaching hardly affected actual net ecosystem carbon balances because of the small solubility of CO 2 in acidic forest soil solutions and large NEE. Leaching of CH 4 proved to be insignificant compared with other fluxes of carbon. Overall, our results show that leaching losses are particularly important for the carbon balance of agricultural systems. 相似文献
11.
Various inhibitors were tested for their inhibitory effects on soybean urease. The Ki values for boric acid, 4-bromophenylboronic acid, butylboronic acid, and phenylboronic acid were 0.20?±?0.05?mM, 0.22?±?0.04?mM, 1.50?±?0.10?mM, and 2.00?±?0.11?mM, respectively. The inhibition was competitive type with boric acid and boronic acids. Heavy metal ions including Ag +, Hg 2+, and Cu 2+ showed strong inhibition on soybean urease, with the silver ion being a potent inhibitor (IC 50 = 2.3?×?10 ?8 mM). Time-dependent inhibition studies exhibited biphasic kinetics with all heavy metal ions. Furthermore, inhibition studies with sodium salts of mineral acids (NaF, NaCl, NaNO 3, and Na 2SO 4) showed that only F ? inhibited soybean urease significantly (IC 50 = 2.9?mM). Competitive type of inhibition was observed for this anion with a Ki value of 1.30?mM. 相似文献
12.
Soil organic matter (SOM) dynamics ultimately govern the ability of soil to provide long‐term C sequestration and the nutrients required for ecosystem productivity. Predicting belowground responses to elevated CO 2 requires an integrated understanding of SOM transformations and the microbial activity that governs them. It remains unclear how the microorganisms upon which these transformations depend will function in an elevated CO 2 world. This study examines SOM transformations and microbial metabolism in soils from the Duke Free Air Carbon Enrichment site in North Carolina, USA. We assessed microbial respiration and net nitrogen (N) mineralization in soils with and without elevated CO 2 exposure during a 100‐day incubation. We also traced the depleted C isotopic signature of the supplemental CO 2 into SOM and the soils' phospholipid fatty acids (PLFA), which serve as biomarkers for living cells. Cumulative net N mineralization in elevated CO 2 soils was 50% that in control soils after a 100‐day incubation. Respiration was not altered with elevated CO 2. C : N ratios of bulk SOM did not change with elevated CO 2, but incubation data suggest that the C : N ratios of mineralized organic matter increased with elevated CO 2. Values of SOM δ13C were depleted with elevated CO 2 (?26.7±0.2 vs. ?30.2±0.3‰), reflecting the depleted signature of the supplemental CO 2. We compared δ13C of individual PLFA with the δ13C of SOM to discern incorporation of the depleted C isotopic signature into soil microbial groups in elevated CO 2 plots. PLFA i15:0, a15:0, and 10Met18:0 reflected significant incorporation of recently produced photosynthate, suggesting that the bacterial groups defined by these biomarkers are active metabolizers in elevated CO 2 soils. At least one of these groups (actinomycetes, 10Met18:0) specializes in metabolizing less labile substrates. Because control plots did not receive an equivalent 13C tracer, we cannot determine from these data whether this group of organisms was stimulated by elevated CO 2 compared with these organisms in control soils. Stimulation of this group, if it occurred in the elevated CO 2 plot, would be consistent with a decline in the availability of mineralizable organic matter with elevated CO 2, which incubation data suggest may be the case in these soils. 相似文献
13.
BackgroundNothing is currently known about microbial composition of saline lakes of the Novosibirsk region and its dependence on physical-chemical parameters of waters. We studied the structure of microbial communities of saline lakes of the Novosibirsk region and the effect of physical-chemical parameters of waters on microbial communities of these lakes. ResultsAccording to the ion content, the lakes were classified either as chloride or chloride-sulfate types. Water salinity ranges from 4.3 to 290 g L−1. Many diverse microbial communities were found. Filamentous and colonial Cyanobacteria of the genera Scytonema, Aphanocapsa, and/or filamentous Algae dominated in littoral communities. Spatial and temporal organization of planktonic microbial communities and the quantities of Archaea and Bacteria were investigated using fluorescent in situ hybridization. We have found that the dominant planktonic component is represented by Archaea, or, less frequently, by Bacteria. Various phylogenetic groups (Bacteria, Archaea, Algae, and Cyanobacteria) are nonuniformly distributed. The principal component analysis was used to detect environmental factors that affect microorganism abundance. We found the principal components responsible for 71.1 % of the observed variation. It was demonstrated that two-block partial least squares was a better method than principal component analysis for analysis of the data. We observed general relationships between microbial abundance and water salinity. ConclusionsWe have performed the first-ever study of the structure of the microbial communities of eleven saline lakes in the Novosibirsk region along with their physical-chemical parameters of waters. Our study demonstrates that saline lakes in the Novosibirsk region contain a unique microbial communities that may become a prolific source of microorganisms for fundamental and applied studies in various fields of ecology, microbiology, geochemistry, and biotechnology, and deserve further metagenomic investigation. 相似文献
14.
To examine trophic dynamics over different size classes, an isotopic study of sailfish Istiophorus platypterus life‐history stages was carried out. Samples were collected from eastern Taiwan and the South China Sea during April 2009 and February 2012. A total of 263 samples (111–245 cm, lower jaw fork length, LLJFL) were examined for changes in trophic structure in relation to LLJFL by using stable isotope analysis of carbon (δ 13C) and nitrogen (δ 15N). The δ 15N values for I. platypterus ranged from 7·51 to 14·19‰ (mean ± s.d . = 12·06 ± 1·16‰) and the δ 13C values ranged from ?22·04 to ?15·48‰ (mean ± s.d . = ?17·62 ± 1·10‰). The δ 15N values were positively dependent on LLJFL ( r2 = 0·377), whereas δ 13C were negatively dependent on LLJFL ( r2 = 0·063). There were significantly different seasonal changes in nitrogen and carbon isotopic concentration, but no significant differences in concentrations between eastern Taiwan and the South China Sea were reported. The trophic level ( TL) of each LLJFL class was correlated, starting from 2·84 TL for size class I ( LLJFL < 140 cm) and reaching 5·03 TL for size class VI ( LLJFL > 221 cm). The mean ± s.d . TL was 4·43 ± 0·19 for all samples. The results reveal that I. platypterus occupies a wide range of trophic levels and different size classes occupy different trophic positions in the pelagic ecosystem. 相似文献
15.
The goals of the study were: (1) to evaluate stable isotopic analysis (SIA) in determining the site fidelity of mummichogs, Fundulus heteroclitus, along a smaller spatial scale (~10?km) in homogenous habitat type relative to previous SIA studies; and (2) to cross-validate SIA results with mark-recapture results from a study conducted concurrently at the same sites in the upper Miramichi River estuary (MRE), New Brunswick, Canada influenced by two pulp mills and three municipal wastewater facilities. Mummichogs sampled at 9 sites along the upper MRE ( n?=?198) had overall mean (± SD) ratios of ?21.03?±?1.45 ‰ δ 13C and 11.37?±?1.02 ‰ δ 15N. Mean δ 13C and δ 15N ratios were significantly different among sites with mean δ 13C increasing in a downstream direction and distinct δ 15N group signatures along the northern and southern shores. Multivariate analyses detected seven distinct groups out of nine sites sampled and these differences appear to be related to wastewater treatment influences, thus demonstrating the utility of SIA as a method to determine the site-specificity of organisms on a relatively small spatial scale within homogenous habitat within an estuary. These results, in addition to the scarcity of statistical outliers (3?%) during examination of isotopic ratios within sites support the results of a previous mark-recapture study that demonstrated very few mummichogs (3.4?%) in the upper MRE move more than 200?m. 相似文献
16.
Archaeal ANaerobic MEthanotrophs (ANME) facilitate the anaerobic oxidation of methane (AOM), a process that is believed to proceed via the reversal of the methanogenesis pathway. Carbon isotopic composition studies indicate that ANME are metabolically diverse and able to assimilate metabolites including methane, methanol, acetate, and dissolved inorganic carbon (DIC). Our data support the interpretation that ANME in marine sediments at methane seeps assimilate both methane and DIC, and the carbon isotopic compositions of the tetrapyrrole coenzyme F430 and the membrane lipids archaeol and hydroxy‐archaeol reflect their relative proportions of carbon from these substrates. Methane is assimilated via the methyl group of CH 3‐tetrahydromethanopterin (H 4MPT) and DIC from carboxylation reactions that incorporate free intracellular DIC. F430 was enriched in 13C (mean δ 13C = ?27‰ for Hydrate Ridge and ?80‰ for the Santa Monica Basin) compared to the archaeal lipids (mean δ 13C = ?97‰ for Hydrate Ridge and ?122‰ for the Santa Monica Basin). We propose that depending on the side of the tricarboxylic acid (TCA) cycle used to synthesize F430, its carbon was derived from 76% DIC and 24% methane via the reductive side or 57% DIC and 43% methane via the oxidative side. ANME lipids are predicted to contain 42% DIC and 58% methane, reflecting the amount of each assimilated into acetyl‐CoA. With isotope models that include variable fractionation during biosynthesis for different carbon substrates, we show the estimated amounts of DIC and methane can result in carbon isotopic compositions of ? 73‰ to ? 77‰ for F430 and ? 105‰ for archaeal lipids, values close to those for Santa Monica Basin. The F430 δ 13C value for Hydrate Ridge was 13C‐enriched compared with the modeled value, suggesting there is divergence from the predicted two carbon source models. 相似文献
17.
Physiological properties of photosynthesis were determined in the marine diatom, Phaeodactylum tricornutum UTEX640, during acclimation from 5% CO 2 to air and related to H 2CO 3 dissociation kinetics and equilibria in artificial seawater. The concentration of dissolved inorganic carbon at half maximum rate of photosynthesis ( K0·5[DIC]) value in high CO 2‐grown cells was 1009 mmol m ? 3 but was reduced three‐fold by the addition of bovine carbonic anhydrase (CA), whereas in air‐grown cells K0·5[DIC] was 71 mmol m ? 3, irrespective of the presence of CA. The maximum rate of photosynthesis ( Pmax) values varied between 300 and 500 μ mol O 2 mg Chl ? 1 h ? 1 regardless of growth pCO 2. Bicarbonate dehydration kinetics in artificial seawater were re‐examined to evaluate the direct HCO 3 ? uptake as a substrate for photosynthesis. The uncatalysed CO 2 formation rate in artificial seawater of 31·65°/ oo of salinity at pH 8·2 and 25 °C was found to be 0·6 mmol m ? 3 min ? 1 at 100 mmol m ? 3 DIC, which is 53·5 and 7·3 times slower than the rates of photosynthesis exhibited in air‐ and high CO 2‐grown cells, respectively. These data indicate that even high CO 2‐grown cells of P. tricornutum can take up both CO 2 and HCO 3 ? as substrates for photosynthesis and HCO 3 ? use improves dramatically when the cells are grown in air. Detailed time courses were obtained of changes in affinity for DIC during the acclimation of high CO 2‐grown cells to air. The development of high‐affinity photosynthesis started after a 2–5 h lag period, followed by a steady increase over the next 15 h. This acclimation time course is the slowest to be described so far. High CO 2‐grown cells were transferred to controlled DIC conditions, at which the concentrations of each DIC species could be defined, and were allowed to acclimate for more than 36 h. The K0·5[DIC] values in acclimated cells appeared to be correlated only with [CO 2(aq)] in the medium but not to HCO 3 ? , CO 32 ? , total [DIC] or the pH of the medium and indicate that the critical signal regulating the affinity of cells for DIC in the marine diatom, P. tricornutum, is [CO 2(aq)] in the medium. 相似文献
18.
Leaks and isotopic disequilibria represent potential errors and artefacts during combined measurements of gas exchange and carbon isotope discrimination (Δ). This paper presents new protocols to quantify, minimize, and correct such phenomena. We performed experiments with gradients of CO 2 concentration (up to ±250 μmol mol ?1) and δ 13C CO2 (34‰), between a clamp‐on leaf cuvette (LI‐6400) and surrounding air, to assess (1) leak coefficients for CO 2, 12CO 2, and 13CO 2 with the empty cuvette and with intact leaves of Holcus lanatus (C 3) or Sorghum bicolor (C 4) in the cuvette; and (2) isotopic disequilibria between net photosynthesis and dark respiration in light. Leak coefficients were virtually identical for 12CO 2 and 13CO 2, but ~8 times higher with leaves in the cuvette. Leaks generated errors on Δ up to 6‰ for H. lanatus and 2‰ for S. bicolor in full light; isotopic disequilibria produced similar variation of Δ. Leak errors in Δ in darkness were much larger due to small biological : leak flux ratios. Leak artefacts were fully corrected with leak coefficients determined on the same leaves as Δ measurements. Analysis of isotopic disequilibria enabled partitioning of net photosynthesis and dark respiration, and indicated inhibitions of dark respiration in full light ( H. lanatus: 14%, S. bicolor: 58%). 相似文献
19.
Glutathione reductase (GR; E.C. 1.6.4.2) is a flavoprotein that catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG). In this study we tested the effects of Al 3+, Ba 2+, Ca 2+, Li +, Mn 2+, Mo 6+, Cd 2+, Ni 2+, and Zn 2+ on purified bovine liver GR. In a range of 10?μM–10?mM concentrations, Al 3+, Ba 2+, Li +, Mn 2+, and Mo 6+, and Ca 2+ at 5?μM–1.25?mM, had no effect on bovine liver GR. Cadmium (Cd 2+), nickel (Ni 2+), and zinc (Zn 2+) showed inhibitory effects on this enzyme. The obtained IC 50 values of Cd 2+, Ni 2+, and Zn 2+ were 0.08, 0.8, and 1?mM, respectively. Cd 2+ inhibition was non-competitive with respect to both GSSG ( KiGSSG 0.221?±?0.02?mM) and NADPH ( KiNADPH 0.113?±?0.008?mM). Ni 2+ inhibition was non-competitive with respect to GSSG ( KiGSSG 0.313?±?0.01?mM) and uncompetitive with respect to NADPH ( KiNADPH 0.932?±?0.03?mM). The effect of Zn 2+ on GR activity was consistent with a non-competitive inhibition pattern when the varied substrates were GSSG ( KiGSSG 0.320?±?0.018?mM) and NADPH ( KiNADPH 0.761?±?0.04?mM), respectively. 相似文献
20.
The cosmopolitan, bloom‐forming diatom, Skeletonema costatum, is a prominent primary producer in coastal oceans, fixing CO 2 with ribulose 1,5‐bisphosphate carboxylase/oxygenase (RubisCO) that is phylogenetically distinct from terrestrial plant RubisCO. RubisCOs are subdivided into groups based on sequence similarity of their large subunits (IA–ID, II, and III). ID is present in several major oceanic primary producers, including diatoms such as S. costatum, coccolithophores, and some dinoflagellates, and differs substantially in amino acid sequence from the well‐studied IB enzymes present in most cyanobacteria and in green algae and plants. Despite this sequence divergence, and differences in isotopic discrimination apparent in other RubisCO enzymes, stable carbon isotope compositions of diatoms and other marine phytoplankton are generally interpreted assuming enzymatic isotopic discrimination similar to spinach RubisCO (IB). To interpret phytoplankton δ 13C values, S. costatum RubisCO was characterized via sequence analysis, and measurement of its KCO2 and Vmax, and degree of isotopic discrimination. The sequence of this enzyme placed it among other diatom ID RubisCOs. Michaelis‐Menten parameters were similar to other ID enzymes ( KCO2 = 48.9 ± 2.8 μm ; Vmax = 165.1 ± 6.3 nmol min ?1 mg ?1). However, isotopic discrimination (ε = [ 12k/ 13k ? 1] × 1000) was low (18.5‰; 17.0–19.9, 95% CI) when compared to IA and IB RubisCOs (22–29‰), though not as low as ID from coccolithophore, Emiliania huxleyi (11.1‰). Variability in ε ‐values among RubisCOs from primary producers is likely reflected in δ 13C values of oceanic biomass. Currently, δ 13C variability is ascribed to physical or chemical factors (e.g. illumination, nutrient availability) and physiological responses to these factors (e.g. carbon‐concentrating mechanisms). Estimating the importance of these factors from δ 13C measurements requires an accurate ε ‐value, and a mass‐balance model using the ε ‐value for S. costatum RubisCO is presented. Clearly, appropriate ε ‐values must be included in interpreting δ 13C values of environmental samples. 相似文献
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