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1.
《Marine Micropaleontology》2010,74(3-4):178-189
Trace elements incorporated in planktonic foraminiferal test carbonate are commonly used as paleoproxies. For instance, Mg/Ca ratios are frequently used for reconstructing sea surface temperature and, together with the foraminiferal stable oxygen isotope ratios, are also used as paleosalinity proxy. Foraminiferal Sr/Ca ratios constitute another example of the application of trace elements in paleostudies since they may reflect the Sr/Ca values of seawater. However, over the past few decades it has been proven that the incorporation of trace elements in foraminiferal calcite is controlled by more than one environmental parameter. To quantify the effect of salinity on Mg and Sr incorporation planktonic foraminifera Globigerinoides sacculifer (sensu stricto) were grown in the laboratory under different environmental conditions. Laboratory experiments allowed us to separate a direct salinity effect from a possible independent impact through differences in the calcite saturation state of the seawater (Ω). Although the temperature effect is more important than the salinity effect, a change of 4 salinity units is equivalent to a 1 °C bias on Mg/Ca-based temperatures. This effect of salinity on Mg incorporation is minor. However, when using Mg/Ca-based temperatures in combination with foraminiferal δ18O to calculate salinity, it cannot be neglected. The present study shows salinity as the overriding control on Mg incorporation within the range of Ω studied (Ω between 5.25 and 6.50; [CO32−] between 218 and 270 μmol/kg) at a constant temperature of 26 °C. In contrast, Ω appears to be the main control on foraminiferal Sr incorporation (0.10 mmol/mol per 100 µmol/kg rise in [CO32−]), whereas salinity has a non significant influence on Sr/Ca. 相似文献
2.
《Marine Micropaleontology》2005,58(1):31-44
Minor and trace elements in foraminiferal carbonates are potential paleo-proxies of climate, nutrient and seawater composition. There are very few reports of trace element composition of symbiont-bearing, larger foraminifera that are known to be important constituents of shallow-marine, modern and ancient carbonates. In this paper we examine the range of variation in Mg and Sr content of Recent species of these foraminifera from a lagoon of Lakshadweep Atoll (Indian Ocean) and Akajima Islands, Japan. Two hyaline species, Amphistegina lessonii and Neorotalia calcar,and two porcellaneous species, Amphisorus hemprichii and Marginopora vertebralis were collected live from Lakshadweep islands. Mg / Ca in these foraminifera is of an order of magnitude higher than the values reported for planktonic and symbiont-free benthic foraminifera. The Sr / Ca values are, however, comparable with the reported values in other foraminiferal taxa and they are found to vary within a narrow range. Electron-probe micro-analysis of three symbiont-bearing benthic species indicates spatial heterogeneity of high orders in Mg / Ca composition in all the species. The annual variation in temperature and pH of the lagoon water cannot explain the observed amplitude of the compositional variation. The photosynthesis and respiration of the symbionts and host foraminifera are possibly the major cause of compositional heterogeneity in individual tests, as has also been recently postulated for symbiont-bearing planktonic foraminiferal species. It highlights the need to isolate biological factors and necessitates species-specific paleotemperature scale in paleoclimatic analysis. We also analyzed δ18O, δ13C, Ca, Mg and Sr in carefully dissected chambers of a reef-dwelling, porcellaneous benthic foraminifer, Marginopora kudakajimaensis, collected live in four seasons. A moderate positive correlation is observed between Mg / Ca and temperature. However, large inter- and intra-test variation in Mg limits the precision of Mg / Ca as palaeotemperature proxy. The Sr / Ca of the test calcite is unrelated to temperature of the sea water. The δ13C of M. kudakajimaensis does not correlate with δ18O, Mg / Ca or Sr / Ca. 相似文献
3.
《Aquatic Botany》2005,81(4):326-342
The effects of NH4+ or NO3− on growth, resource allocation and nitrogen (N) uptake kinetics of two common helophytes Phragmites australis (Cav.) Trin. ex Steudel and Glyceria maxima (Hartm.) Holmb. were studied in semi steady-state hydroponic cultures. At a steady-state nitrogen availability of 34 μM the growth rate of Phragmites was not affected by the N form (mean RGR = 35.4 mg g−1 d−1), whereas the growth rate of Glyceria was 16% higher in NH4+-N cultures than in NO3−-N cultures (mean = 66.7 and 57.4 mg g−1 d−1 of NH4+ and NO3− treated plants, respectively). Phragmites and Glyceria had higher S/R ratio in NH4+ cultures than in NO3− cultures, 123.5 and 129.7%, respectively.Species differed in the nitrogen utilisation. In Glyceria, the relative tissue N content was higher than in Phragmites and was increased in NH4+ treated plants by 16%. The tissue NH4+ concentration (mean = 1.6 μmol g fresh wt−1) was not affected by N treatment, whereas NO3− contents were higher in NO3− (mean = 1.5 μmol g fresh wt−1) than in NH4+ (mean = 0.4 μmol g fresh wt−1) treated plants. In Phragmites, NH4+ (mean = 1.6 μmol g fresh wt−1) and NO3− (mean = 0.2 μmol g fresh wt−1) contents were not affected by the N regime. Species did not differ in NH4+ (mean = 56.5 μmol g−1 root dry wt h−1) and NO3− (mean = 34.5 μmol g−1 root dry wt h−1) maximum uptake rates (Vmax), and Vmax for NH4+ uptake was not affected by N treatment. The uptake rate of NO3− was low in NH4+ treated plants, and an induction phase for NO3− was observed in NH4+ treated Phragmites but not in Glyceria. Phragmites had low Km (mean = 4.5 μM) and high affinity (10.3 l g−1 root dry wt h−1) for both ions compared to Glyceria (Km = 6.3 μM, affinity = 8.0 l g−1 root dry wt h−1). The results showed different plasticity of Phragmites and Glyceria toward N source. The positive response to NH4+-N source may participates in the observed success of Glyceria at NH4+ rich sites, although other factors have to be considered. Higher plasticity of Phragmites toward low nutrient availability may favour this species at oligotrophic sites. 相似文献
4.
Two tetracyanometalate building blocks, [Fe(5,5′-dmbipy)(CN)4]? (2) and [Fe(4,4′-dmbipy)(CN)4]? (3) (5,5′-dmbipy = 5,5′-dimethyl-2,2′-bipyridine; 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine), and two cyano-bridged heterobimetallic complexes, [Cu2(bpca)2(H2O)2Fe2(5,5′-dmbipy)2(CN)8] · 2[Cu(bpca)Fe(5,5′-dmbipy)(CN)4] · 4H2O (4) and [Cu(bpca)Fe(4,4′-dmbipy)(CN)4]n (5) (bpca = bis(2-pyridylcarbonyl)amidate), have been synthesized and structurally characterized. Complex 4 contains two dinuclear and one tetranuclear heterobimetallic clusters in an asymmetric unit whereas the structure of complex 5 features a one-dimensional heterobimetallic zigzag chain. The Cu(II) ion is penta-coordinated in the form of a distorted square-based pyramid. Magnetic studies show ferromagnetic coupling between Cu(II) and Fe(III) ions with g = 2.28, J1 = 2.64 cm?1, J2 = 5.40 cm?1 and TIP = ?2.36 × 10?3 for complex 4, and g = 2.17, J = 4.82 cm?1 and zJ′ = 0.029 cm?1 for complex 5. 相似文献
5.
Xylitol-2-dehydrogenase from Candida albicans was cloned and overexpressed in Escherichia coli. The purified recombinant XDH has an apparent molecular weight of 40 kDa which belongs to the medium chain alcohol dehydrogenase family and exclusively uses NAD+ as a cofactor. The recombinant caXDH has a KM of 8.8 mM and 37.7 μM using the substrate xylitol and NAD+, respectively, and its catalytic efficiency is 53,200 min?1 mM?1. Following site-directed mutagenesis, one of the engineered caXDHs with six mutations at Ser95Cys, Ser98Cys, Tyr101Cys, Asp206Ala, Ile207Arg, and Phe208Ser shifted its cofactor dependence from NAD+ to NADP+ in which the KM and kcat/KM towards NADP+ are 119 μM and 26,200 min?1 mM?1, respectively. 相似文献
6.
Joel N. Schrauben Dong Guo John L. McCracken James K. McCusker 《Inorganica chimica acta》2008,361(12-13):3539-3547
The bimetallic [M1M2(tren)2(CAn?)]m+ series, where M = GaIII or CrIII and CA is the chloranilate ligand which can take on diamagnetic (CAcat,cat)4? or paramagnetic (CAsq,cat)3? forms, comprises an electronically diverse series of compounds ranging from the closed-shell [Ga2(tren)2(CAcat,cat)]2+ to the S = 5/2 ground state of [Cr2(tren)2(CAsq,cat)]3+. This report deals with the interpretation of the EPR and ENDOR spectra of [Ga2(tren)2(CAsq,cat)](BPh4)2(BF4) (2) and the related derivative [Ga2(tren)2(DHBQ)](BPh4)2(BF4) (2a) (where DHBQ is the fully deprotonated trianionic form of 2,5-dihydroxy-1,4-benzoquinone) in an effort to further characterize the electronic structure of this radical species. The X-band (~9.5 GHz) EPR spectrum of complex 2 acquired in a butyronitrile/propionitrile glass at 4 K reveals a rhombic g-tensor with gxx = 2.0100, gyy = 2.0097, and gzz = 2.0060 with hyperfine interactions due to spin delocalization onto the two Ga nuclei (axx = 4.902 G, ayy = 4.124 G, azz = 3.167 G); the origin of the hyperfine coupling was confirmed by analysis of the room temperature spectra of complexes 2 and 2a. The low-temperature spectrum of complex 2 also indicates the presence of a triplet electronic state characterized by a g-value of 2.009 and axial zero-field splitting of D = 150 G (0.012 cm?1) as determined from measurements carried out at both X- and W-band (~95 GHz) frequencies. This triplet state is believed to arise due to a weak intermolecular Heisenberg exchange interaction between two aggregating complexes. ENDOR measurements on complex 2a at 20 K allowed for a determination of the magnitude of hyperfine coupling to the protons associated with the radical bridge as well as providing a rare example of an ENDOR signal arising from coupling to a gallium nucleus. Finally, these results were combined with literature data on the free semiquinone form of the bridging ligand in order to assess the extent to which density functional theory can predict unpaired spin density distribution in a complex molecule of this type. Although differences between theory and experiment were noted, DFT was able to provide a reasonably accurate picture of the electronic structure of this system as well as provide insight into the spin polarization mechanism(s) responsible for the observed hyperfine interactions. 相似文献
7.
Altaf Hussain Muhammad Hamid Rashid Raheela Perveen Muhammad Ashraf 《Plant Physiology and Biochemistry》2009,47(3):188-194
We report for the first time kinetic and thermodynamic properties of soluble acid invertase (SAI) of sugarcane (Saccharum officinarum L.) salt sensitive local cultivar CP 77-400 (CP-77). The SAI was purified to apparent homogeneity on FPLC system. The crude enzyme was about 13 fold purified and recovery of SAI was 35%. The invertase was monomeric in nature and its native molecular mass on gel filtration and subunit mass on SDS-PAGE was 28 kDa. SAI was highly acidic having an optimum pH lower than 2. The acidic limb was missing. Proton transfer (donation and receiving) during catalysis was controlled by the basic limb having a pKa of 2.4. Carboxyl groups were involved in proton transfer during catalysis. The kinetic constants for sucrose hydrolysis by SAI were determined to be: km = 55 mg ml?1, kcat = 21 s?1, kcat/km = 0.38, while the thermodynamic parameters were: ΔH* = 52.6 kJ mol?1, ΔG* = 71.2 kJ mol?1, ΔS* = ?57 J mol?1 K?1, ΔG*E–S = 10.8 kJ mol?1 and ΔG*E–T = 2.6 kJ mol?1. The kinetics and thermodynamics of irreversible thermal denaturation at various temperatures 53–63 °C were also determined. The half -life of SAI at 53 and 63 °C was 112 and 10 min, respectively. At 55 °C, surprisingly the half -life increased to twice that at 53 °C. ΔG*, ΔH* and ΔS* of irreversible thermal stability of SAI at 55 °C were 107.7 kJ mol?1, 276.04 kJ mol?1 and 513 J mol?1K?1, respectively. 相似文献
8.
Atriplex (Halimione) portulacoides is a halophyte with potential interest for saline soil reclamation and phytoremediation. Here, we assess the impact of salinity reaching up to two-fold seawater concentration (0–1000 mM NaCl) on the plant growth, leaf water status and ion uptake and we evaluate the contribution of inorganic and organic solutes to the osmotic adjustment process. A. portulacoides growth was optimal at 200 mM NaCl but higher salinities (especially 800 and 1000 mM NaCl) significantly reduced plant growth. Na+ and Cl− contents increased upon salt exposure especially in the leaves compared to the roots. Interestingly, no salt-induced toxicity symptoms were observed and leaf water content was maintained even at the highest salinity level. Furthermore, leaf succulence and high instantaneous water use efficiency (WUEi) under high salinity significantly contributed to maintain leaf water status of this species. Leaf pressure–volume curves showed that salt-challenged plants adjusted osmotically by lowering osmotic potential at full turgor (Ψπ100) along with a decrease in leaf cell elasticity (values of volumetric modulus elasticity (ε) increased). As a whole, our findings indicate that A. portulacoides is characterized by a high plasticity in terms of salt-response. Preserving leaf hydration and efficiently using Na+ for the osmotic adjustment especially at high salinities (800–1000 mM NaCl), likely through its compartmentalization in leaf vacuoles, are key determinants of such a performance. The selective absorption of K+ over Na+ in concomitance with an increase in the K+ use efficiency also accounted for the overall plant salt tolerance. 相似文献
9.
W. Gary Anderson Patricia J. Dasiewicz Suadi Liban Calen Ryan Josi R. Taylor Martin Grosell Dirk Weihrauch 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2010,155(4):493-502
The present study reports aspects of GI tract physiology in the white-spotted bamboo shark, Chiloscyllium plagiosum, little skate, Leucoraja erinacea and the clear nose skate, Raja eglanteria. Plasma and stomach fluid osmolality and solute values were comparable between species, and stomach pH was low in all species (2.2 to 3.4) suggesting these elasmobranchs may maintain a consistently low stomach pH. Intestinal osmolality, pH and ion values were comparable between species, however, some differences in ion values were observed. In particular Ca2+ (19.67 ± 3.65 mM) and Mg2+ (43.99 ± 5.11 mM) were high in L. erinacea and Mg2+ was high (130.0 ± 39.8 mM) in C. palgiosum which may be an indication of drinking. Furthermore, intestinal fluid HCO3? values were low (8.19 ± 2.42 and 8.63 ± 1.48 mM) in both skates but very high in C. plagiosum (73.3 ± 16.3 mM) suggesting ingested seawater may be processed by species-specific mechanisms. Urea values from the intestine to the colon dropped precipitously in all species, with the greatest decrease seen in C. plagiosum (426.0 ± 8.1 to 0 mM). This led to the examination of the molecular expression of both a urea transporter and a Rhesus like ammonia transporter in the intestine, rectal gland and kidney in L. erinacea. Both these transporters were expressed in all tissues; however, expression levels of the Rhesus like ammonia transporter were orders of magnitude higher than the urea transporter in the same tissue. Intestinal flux rates of solutes in L. erinacea were, for the most part, in an inward direction with the notable exception of urea. Colon flux rates of solutes in L. erinacea were all in an outward direction, although absolute rates were considerably lower than the intestine, suggestive of a much tighter epithelia. Results are discussed in the context of the potential role of the GI tract in salt and water, and nitrogen, homeostasis in elasmobranchs. 相似文献
10.
Agnieszka Kubiak Piotr Jakimowicz Antoni Polanowski 《International journal of biological macromolecules》2009,45(2):194-199
Low-molecular-mass trypsin inhibitor (clTI-1; chicken liver Trypsin Inhibitor-1) was purified from chicken liver by extraction with perchloric acid, ammonium sulfate precipitation, a combination of ethanol-acetone fractionation followed by gel filtration, ion-exchange chromatography and RP-HPLC on a C18 column. The inhibitor occurs in two isoforms with molecular masses of 5938.56 and 6026.29 Da (determined by MALDI TOFF mass spectrometry). The complete amino acid sequences of both isoforms were determined (UniProtKB/Swiss-Prot P85000; ISK1L_CHICK). The inhibitor shows a high homology to Kazal-type family inhibitors, especially to trypsin/acrosin inhibitors and pancreatic secretory trypsin inhibitors. clTI-1 inhibits both bovine and porcine trypsin (Ka = 1.1 × 109 M?1 and 2.5 × 109 M?1, respectively). Significant differences were shown in the inhibition of the anionic and cationic forms of chicken trypsin (Ka = 4.5 × 108 M?1 and 1.2 × 1010 M?1). Weak interaction with human plasmin (Ka = 1.2 × 107 M?1) was also revealed. 相似文献
11.
Saeid Ghorbanzadeh Mashkani Parisa Tajer Mohammad Ghazvini 《Bioresource technology》2009,100(6):1915-1921
The presence of Cs and Sr in culture medium of Azolla filiculoides caused about 27.4% and 46.3% inhibition of biomass growth, respectively, in comparison to A. filiculoides control weight which had not metals. Biosorption batch experiments were conducted to determine the Cs and Sr binding ability of native biomass and chemically modified biosorbents derived from Azolla namely ferrocyanide Azolla sorbents type 1 and type 2 (FAS1 and FAS2) and hydrogen peroxide Azolla sorbent (HAS). The best Cs and Sr removal results were obtained when A. filiculoides was treated by 2 M MgCl2 and 30 ml H2O2 8 mM at pH 7 for 12 h and it was then washed by NaOH solution at pH 10.5 for 6 h. Pretreatment of Azolla have been suggested to modify the surface characteristics which could improve biosorption process. The binding of Cs and Sr on the cell wall of Azolla was studied with micro-PIXE and FT-IR. 相似文献
12.
《Aquatic Botany》2007,87(2):104-110
A large-scale mesocosm (sixteen 500 L tanks) experiment was conducted to investigate the effects of hypersalinity (45–65 psu), porewater sulfide (2–6 mM) and nighttime water column hypoxia (5–3 mg L−1) on the tropical seagrass Thalassia testudinum Banks ex König. We examined stressor effects on growth, shoot survival, tissue sulfur (S0, TS, δ34S) and leaf quantum efficiencies, as well as, porewater sulfides (∑TSpw) and mesocosm water column O2 dynamics. Sulfide was injected into intact seagrass cores of T. testudinum exposing below-ground tissues to 2, 4, and 6 mM S2−, but rapid oxidation resulted in ∑TSpw < 1.5 mM. Hypersalinity at 65 psu lowered sulfide oxidation and significantly affected plant growth rates and quantum efficiencies (Fv/Fm < 0.70). The most depleted rhizome δ34S signatures were also observed at 65 psu, suggesting increased sulfide exposure. Hypoxia did not influence ∑TSpw and plant growth, but strengthened the hypersalinity response and decreased rhizome S0, indicating less efficient oxidation of ∑TSpw. Following nighttime hypoxia treatments, ecosystem level metabolism responded to salinity treatments. When O2 levels were reduced to 5 and 4 mg L−1, daytime O2 levels recovered to approximately 6 mg L−1; however, this recovery was more limited when O2 levels were lowered to 3 mg L−1. Subsequent to O2 reductions to 3 mg O2 L−1, nighttime O2 levels rose in the 35 and 45 psu tanks, stayed the same in the 55 psu tanks, and declined in the 65 psu tanks. Thus, hypersalinity at 65 psu affects T. testudinum's oxidizing capacity and places subtle demands on the positive O2 balance at an ecosystem level. This O2 demand may influence T. testudinum die-off events, particularly after periods of high temperature and salinity. We hypothesize that the interaction between hypersalinity and sulfide toxicity in T. testudinum is their synergistic effect on the critical O2 balance of the plant. 相似文献
13.
《Aquatic Botany》2007,87(4):292-298
The effect of salinity on leaf area and the relative accumulation of Na+ and K+ in leaves of the mangrove associate Hibiscus tiliaceus were investigated. Photosynthetic gas exchange characteristics were also examined under arid and non-arid leaf conditions at 0, 10, 20 and 30‰ substrate salinity. At salinities ≥ 40‰, plants showed complete defoliation followed by 100% mortality within 1 week. Salinities ≤ 30‰ were negatively correlated with the total leaf area per plant (r2 = 0.94). The reduction in the total plant leaf area is attributed to the reduction in the area of individual leaves (r2 = 0.94). Selective uptake of K+ over Na+ declined sharply with increasing salinity, where K+/Na+ ratio was reduced from 6.37 to 0.69 in plants treated with 0 and 30‰, respectively. Under non-arid leaf condition, increasing salinity from 0 to 30‰ has significantly reduced the values of the intrinsic components of photosynthesis Vc,max (from 50.4 to 18.4 μmol m−2 s-1), Jmax (from 118.0 to 33.8 μmol photons m−2 s−1), and VTPU (from 6.90 to 2.30 μmol m−2 s−1), while stomatal limitation to gas phase conductance (SL) increased from 14.6 to 38.4%. Water use efficiency (WUE) has subsequently doubled from 3.20 for the control plants to 8.93 for 30‰ treatment. Under arid leaf conditions, the stomatal factor (SL) was more limiting to photosynthesis than its biochemical components (73.4 to 26.6%, respectively, at 30‰). It is concluded that salinity causes a drastic decline in photosynthetic gas exchange in H. tiliaceus leaves through its intrinsic and stomatal components, and that the apparent phenotypic plasticity represented by the leaf area modulation is unlikely to be the mechanism by which H. tiliaceus avoids salt stress. 相似文献
14.
《Process Biochemistry》2014,49(3):445-450
A cyanide hydratase from Aspergillus niger K10 was expressed in Escherichia coli and purified. Apart from HCN, it transformed some nitriles, preferentially 2-cyanopyridine and fumaronitrile. Vmax and Km for HCN were ca. 6.8 mmol min−1 mg−1 protein and 109 mM, respectively. Vmax for fumaronitrile and 2-cyanopyridine was two to three orders of magnitude lower than for HCN (ca. 18.8 and 10.3 μmol min−1 mg−1, respectively) but Km was also lower (ca. 14.7 and 3.7 mM, respectively). Both cyanide hydratase and nitrilase activities were abolished in truncated enzyme variants missing 18–34 C-terminal aa residues. The enzyme exhibited the highest activity at 45 °C and pH 8–9; it was unstable at over 35 °C and at below pH 5.5. The operational stability of the whole-cell catalyst was examined in continuous stirred membrane reactors with 70-mL working volume. The catalyst exhibited a half-life of 5.6 h at 28 °C. A reactor loaded with an excess of the catalyst was used to degrade 25 mM KCN. A conversion rate of over 80% was maintained for 3 days. 相似文献
15.
《Environmental and Experimental Botany》2006,55(3):256-266
The present study demonstrates the influence of the duration of periodical waterlogging with artificial seawater on the photosynthetic and physiological responses of Kandelia candel L. Druce seedlings, the pre-dominant species of subtropical mangroves in China. Artificial tidal fluctuations applied here closely mimicked the twice daily tidal inundation which mangroves experience in the field. All the seedlings were immersed in artificial seawater during 70-day cultivation. Similar trends with increasing duration of immersion occurred in photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration, where significant decreases occurred only in long time treatments of 10 or 12 h. Water used efficiency and chlorophyll contents showed lower in medium periods and higher in long periods of immersion. This indicates that the increase in pigment contents of leaves was ineffective in promoting Pn under long time immersion. Light saturation points under short time waterlogging (0–4 h) occurred at light intensities of 800–1000 μmol/m2/s, and at around 400 μmol/m2/s in long time treatments (8–12 h). Long periods of tidal immersion therefore significantly inhibited photosynthesis of mature leaves. Alcohol dehydrogenase and oxidase activity in roots both increased under longer immersion periods, suggesting that roots are sensitive to anaerobiosis under long term waterlogging. The activities of peroxidase and superoxide dismutase in mature leaves increased in 8 h and 10 h treatments, respectively. The content of malondialdehyde in mature leaves increased under long time treatments. Abscisic acid accumulation in mature leaves also had a sharp increase from 8 h to 12 h inundation. Even though the anti-oxidative enzymes were induced by waterlogging, this was not sufficient to protect the seedlings from senescence. The results suggested that K. candel seedlings completely tolerated tidal immersion by seawater up to about 8 h in each cycle, which matches the natural distribution of K. candel in inter-tidal zones of China. 相似文献
16.
《Harmful algae》2017
The algicidal and growth-inhibiting bacteria associated with seagrasses and macroalgae were characterized during the summer of 2012 and 2013 throughout Puget Sound, WA, USA. In 2012, Heterosigma akashiwo-killing bacteria were observed in concentrations of 2.8 × 106 CFU g−1 wet in the outer organic layer (biofilm) on the common eelgrass (Zostera marina) in north Padilla Bay. Bacteria that inhibited the growth of Alexandrium tamarense were detected within the biofilm formed on the eelgrass canopy at Dumas Bay and North Bay at densities of ∼108 CFU g−1 wet weight. Additionally, up to 4100 CFU mL−1 of algicidal and growth-inhibiting bacteria affecting both A. tamarense and H. akashiwo were detected in seawater adjacent to seven different eelgrass beds. In 2013, H. akashiwo-killing bacteria were found on Z. marina and Ulva lactuca with the highest densities of ∼108 CFU g−1 wet weight at Shallow Bay, Sucia Island. Bacteria that inhibited the growth of H. akashiwo and A. tamarense were also detected on Z. marina and Z. japonica at central Padilla Bay. Heterosigma akashiwo cysts were detected at a concentration of 3400 cysts g−1 wet weight in the sediment from Westcott Bay (northern San Juan Island), a location where eelgrass disappeared in 2002. These findings provide new insights on the ecology of algicidal and growth-inhibiting bacteria, and suggest that seagrass and macroalgae provide an environment that may influence the abundance of harmful algae in this region. This work highlights the importance of protection and restoration of native seagrasses and macroalgae in nearshore environments, in particular those regions where shellfish restoration initiatives are in place to satisfy a growing demand for seafood. 相似文献
17.
《Peptides》2013
The host-defense peptide, esculentin-2CHa (GFSSIFRGVA10KFASKGLGK D20LAKLGVDLVA30 CKISKQC) shows potent (MIC ≤ 6 μM) growth inhibitory activity against clinical isolates of multidrug-resistant strains of Staphylococcus aureus, Acinetobacter baumannii, and Stenotrophomonas maltophilia and differential cytotoxic activity against human erythrocytes (LC50 = 150 μM) and human non-small cell lung adenocarcinoma A549 cells (LC50 = 10 μM). Esculentin-2CHa significantly (P < 0.01) stimulates the release of the anti-inflammatory cytokine IL-10 by mouse lymphoid cells and elevates its production after stimulation with concanavalin A and significantly (P < 0.05) stimulates TNF-α production by peritoneal macrophages. Effects on IL-6 and IL-1β production were not significant. Removal of the hydrophobic N-terminal hexapeptide (GFSSIF) from esculentin-2CHa results in abolition of growth inhibitory activity against S. aureus and cytotoxic activity against erythrocytes and A549 cells as well as a marked (≥16-fold) reduction in potency against A. baumannii and S. maltophilia. The primary structure of esculentin-2 has been poorly conserved between frog species but evolutionary pressure has acted to maintain the hydrophobic character of this N-terminal hexapeptide sequence. Removal of the cyclic C-terminal domain (CKISKQC) and replacement of the Cys31 and Cys37 residues by serine resulted in appreciable decreases in cytotoxicity against all microorganisms and against mammalian cells. The more cationic [D20K, D27K] analog showed a modest increase in potency against all microorganisms (up to 4-fold) but a marked increase in cytotoxicity against erythrocytes (LC50 = 11 μM) and A549 cells (LC50 = 3 μM). 相似文献
18.
《Aquatic Botany》2005,82(1):55-70
A study of the meadows of the invasive Caulerpa racemosa var. cylindracea (Sonder) Verlaque, Huisman et Boudouresque was carried out over one year at Marseilles (Provence, France) where the alga is thriving, probably since 1994, in the cold waters of the north western Mediterranean Sea. At an early phase of colonisation, the C. racemosa meadow is characterized by a patchy distribution pattern. Several years are necessary to obtain a dense and continuous meadow. In one area colonized for more than 4 years, C. racemosa has developed a continuous meadow with wide seasonal variations. Maximum development was reached in autumn (biomass: 82 ± 3 g DW m−2; length of stolons: 1162 ± 86 m m−2; number of apices: 8360 ± 405 m−2; number of erect axes: 20955 ± 1499 m−2) and the minimum from winter to early spring (respectively, 0.3 ± 0.1 g DW m−2; 3 ± 1 m m−2; 220 ± 55 apices m−2; 35 ± 15 erect axes m−2). Seasonal variations in the growth rate were highly significant. The season of high growth lasted from June to October. The apical growth rate of a stolon reached a maximum of 7.5 ± 0.3 mm day−1 in early October, then began to decrease significantly from the end of October to December, before becoming nearly nil from January to early May. Annual net production rate expressed in terms of stolon length and biomass was estimated as 5801 m m−2 a−1 and 612 g DW m−2 a−1, respectively. During the growth period, the turnover rate of the C. racemosa stolons was estimated at from 25 to 46 days. The growth rate was closely correlated to the seawater temperature (R2 = 0.83), whereas no significant correlation was found between growth and irradiance. During the growth period, a decrease in temperature rapidly affects the growth rate, which soon recovers its earlier level when the temperature rises again. In winter, the growth rate decreased rapidly with the seasonal drop in the seawater temperature. Grazing by fish (Sarpa salpa and Boops boops) can also affect the growth rate from September to December by consumption of the erect axes and stolon apices, enhancing the ramification of stolons. Seasonal changes at Marseilles are much sharper than those reported for warmer Mediterranean localities (French Riviera, Italy, Croatia): in winter and early spring C. racemosa meadows decreased and locally disappeared, leaving a barren substrate. C. racemosa survives the lower winter seawater temperatures of the north-western Mediterranean Sea probably in the form of zygotes and/or small fragments (rhizoids, stolons, propagules). 相似文献
19.
《Aquatic Botany》2008,88(4):292-298
The effect of salinity on leaf area and the relative accumulation of Na+ and K+ in leaves of the mangrove associate Hibiscus tiliaceus were investigated. Photosynthetic gas exchange characteristics were also examined under arid and non-arid leaf conditions at 0, 10, 20 and 30‰ substrate salinity. At salinities ≥ 40‰, plants showed complete defoliation followed by 100% mortality within 1 week. Salinities ≤ 30‰ were negatively correlated with the total leaf area per plant (r2 = 0.94). The reduction in the total plant leaf area is attributed to the reduction in the area of individual leaves (r2 = 0.94). Selective uptake of K+ over Na+ declined sharply with increasing salinity, where K+/Na+ ratio was reduced from 6.37 to 0.69 in plants treated with 0 and 30‰, respectively. Under non-arid leaf condition, increasing salinity from 0 to 30‰ has significantly reduced the values of the intrinsic components of photosynthesis Vc,max (from 50.4 to 18.4 μmol m−2 s-1), Jmax (from 118.0 to 33.8 μmol photons m−2 s−1), and VTPU (from 6.90 to 2.30 μmol m−2 s−1), while stomatal limitation to gas phase conductance (SL) increased from 14.6 to 38.4%. Water use efficiency (WUE) has subsequently doubled from 3.20 for the control plants to 8.93 for 30‰ treatment. Under arid leaf conditions, the stomatal factor (SL) was more limiting to photosynthesis than its biochemical components (73.4 to 26.6%, respectively, at 30‰). It is concluded that salinity causes a drastic decline in photosynthetic gas exchange in H. tiliaceus leaves through its intrinsic and stomatal components, and that the apparent phenotypic plasticity represented by the leaf area modulation is unlikely to be the mechanism by which H. tiliaceus avoids salt stress. 相似文献
20.
Cumulative ozone uptake (COU, mmol m−2) and O3 flux (FO3, nmol m−2 s−1) were related to physiological, morphological and biochemical characteristics of field-grown mature evergreen Norway spruce [Picea abies (L.) Karst.], Cembran pine [Pinus cembra L.], and deciduous European larch [Larix decidua Mill.] trees at treeline. The threshold COU causing a statistically significant decline in photosynthetic capacity (Amax) ranged between 19.6 mmol m−2 in current-year needles of evergreen conifers and 22.0 6 mmol m−2 in short-shoot needles of deciduous L. decidua subjected to exposure periods of ≥84 and ≥43 days, respectively. The higher O3 sensitivity of deciduous L. decidua than of evergreen P abies and P. cembra was associated with differences in FO3 and specific leaf area (SLA), both being significantly higher in L. decidua. FO3 was 5.9 nmol m−2 s−1 in L. decidua and 2.7 nmol m−2 s−1 in evergreen conifers. Species-dependent differences were also related to detoxification capacity expressed through total surface area based concentrations of reduced ascorbate and α-tocopherol that both increased with SLA. Findings suggest that differences in O3 sensitivity between evergreen and deciduous conifers can be attributed to foliage type specific differences in SLA, the latter determining physiological and biochemical characteristics of the treeline conifers. 相似文献