The interrelationship between HCO 3 − , NO 3 − , and Cl− as effective anions in the photosynthetic electron transport

Thylakoids were isolated from the leaves of three different plants (Pisum sativium L., Lactuca sativa L., and Raphanus sativus L.). The addition of HCO ₃ ^? to a suspension of salt-and HCO ₃ ^? -epleted thylakoids (suspended in salt-free medium) raised the rate of O₂ evolution up to fourfold. This stimulation could be partially replaced by the addition of chloride or nitrate ions. However, the addition of HCO ₃ ^? in the presence of Cl^? or NO ₃ ^? resulted in a higher stimulation of O₂ evolution (sixfold in the presence of nitrate and sevenfold in the presence of chloride). On the other hand, the addition of HCO ₃ ^? to the thylakoids depleted from salt only raised the rate of O₂ evolution by 10–15%, whereas 40–70% was obtained by the addition of nitrate or chloride ions. The fluorescence induction studies indicated a significant decrease in the yield of the variable fluorescence of the salt- and HCO ₃ ^? -depleted thylakoids. A partial increase in the fluorescence yield was obtained by the addition of HCO ₃ ^? alone. A typical fluorescence induction curves were obtained by the addition of HCO ₃ ^? in the presence of Cl^? or NO ₃ ^? ions. The data obtained suggest a similar role for chloride and nitrate ions in O₂ evolution in the Hill-reaction, which is restricted at the donor side of photosystem II, whereas bicarbonate plays its role at both sides (acceptor and donor sides). The presented data are those obtained for the thylakoids of P. sativium, which were more or less similar to those obtained for L. sativa and R. sativus.     

Comparison of in-situ biodegrading abilities of Pseudomonas putida mutants: leuB− auxotroph,fliC− non-motility,and cheA− non-chemotaxis

Bioremediation of pollutants in natural environments is affected by many factors, such as bacterial survival, motility, and chemotaxis. However, these roles in in-situ biodegradation of organophosphorus pesticides have not been examined extensively. In this paper, a highly effective methyl-parathion (MP) degrading strain, Pseudomonas putida DLL-1, which also demonstrates motile ability and chemotactic response toward MP, was selected as the research material. A leuB^? auxotroph mutant A3-27 and fliC^? non-motility mutant a4-8 were first constructed by random insertion of the kanamycin gene into the chromosome of P. putida DLL-1 with the mini-transposon system. Biodegradation of MP in liquid medium and soil microcosms by A3-27, a4-8 and a previously constructed cheA^? non-chemotaxis mutant P. putida DAK were compared. The kinetic parameters for MP degradation were all similar in the well-mixed liquid systems. However, in soil microcosms, all the three mutants had lower degrading rates compared with wild-type P. putida DLL-1. The auxotroph mutant A3-27 had the lowest degrading rate and could only degrade 25.7–34.2% MP in 5 days, and the non-motility mutant a4-8 and non-chemotaxis mutant DAK could only degrade 53.5–68.1% and 64.3–85.7% MP, respectively. This paper emphasizes, for the first time, the use of non-auxotroph bacteria for efficient removal of organophosphorus pesticides in contaminated sites, and also points out the importance of select microorganisms with specific motile or chemotactic affinities in optimizing pesticide bioremediation.     

Structural studies of an Inv (1, −2) kappa light chain

A Bence Jones protein with phenotype Inv (1, –2) was isolated from the urine of a patient with multiple myeloma. Inv typing of the patient's relatives established the presence of anInv ¹ allele in the kindred, and that the patient's genotype wasInv ¹/Inv ³. Hence, the absence of Inv (2) in the Bence Jones protein was shown to be genetic and not an artifact caused by the disease. The tryptic peptide-containing residues 191 through 194 were isolated and shown to be composed of Leu, Tyr, Ala, Cys, with Leu at the amino end. Hence, the residue at 191 is the same as that present in Inv (1, 2) Bence Jones proteins. More detailed study of the tryptic peptides established that residue 153 is Val rather than Ala as in all other K chains thus far studied. The primary sequence: Ala¹⁵³, Leu¹⁹¹ determines Inv (1, 2); Ala¹⁵³, Val¹⁹¹ determines Inv (3); and Val¹⁵³, Leu¹⁹¹ determines Inv (1). The Val¹⁵³, Val¹⁹¹ sequence has not been observed. It may correspond to Inv (–). These data are strikingly similar to the data for the Kern and Oz isotypes (changes at 154 and 191, respectively) in the chain. As in the case of theK chain, only three of the four possible combinations have been observed. The implications of this parallelism and of crystallographic findings on chains, reported by others, are discussed.     

pH dependent stabilization of S2QA − and S2QB − charge pairs studied by thermoluminescence

The pH dependence of emission peak temperature and decay time of thermoluminescence arising from S₂Q_B ^– and S₂Q_A ^– recombinations demonstrates that a stabilization of S₂Q_B ^– occurs at low pH whereas stabilization of S₂Q_A ^– occurs at high pH. Based on comparative analysis of thermoluminescence parameters of the two types of recombination, we suggest that in the pH range between 5.3 and 7.5, E_m(S₂/S₁) and E_m(Q_A/Q_A ^–) are constant, but E_m(Q_B/Q_B ^–) gradually increases with decreasing pH, while in the pH range between 7.5 and 8.5, an unusual change occurs on S₂Q_A ^– charge pair, which is interpreted as either a decrease in E_m(S₂/S₁) or an increase in E_m(Q_A/Q_A ^–).     

Structures and aromaticity of X2Y 2 − (X = C, Si, Ge and Y = N, P, As) anions

The equilibrium geometries, total energies, and vibrational frequencies of anions X₂Y₂ ⁻ (X = C, Si, Ge and Y = N, P, As) are theoretically investigated with density functional theory (DFT) method. Our calculation shows that for C₂N₂ ⁻ species, the D _2h isomer is the most stable four-membered structure, and for other species the C _2v isomer in which two X atoms are contrapuntal is the most stable structure at the B3LYP/6-311 +G_* level. Wiberg bond index (WBI) and negative nucleus-independent chemical shift (NICS) value indicate the existence of delocalization in stable X₂Y₂ ⁻ structures. A detailed molecular orbital (MO) analysis further reveals that stable isomers of these species have strongly aromatic character, which strengthens the structural stability and makes them closely connected with the concept of aromaticity.     

Biosynthesis of indole-3-acetic acid in tomato shoots: Measurement,mass-spectral identification and incorporation of −2H from −2H2O into indole-3-acetic acid,d- and l-tryptophan,indole-3-pyruvate and tryptamine

Indole-3-acetic acid (IAA) and its putative precursors, l- and d-tryptophan, indole-3-pyruvate, and tryptamine were isolated from tomato (Lycopersicon esculentum (L.) Mill.) shoots, identified by mass spectrometry, and measured using capillary gas chromatography with an electron capture detector and radioactive internal standards. Average amounts present were 7.9ng · (g FW)^–-1 IAA, 5.7ng · (g FW)^–-1 indole-3-pyruvate, 132 ng · (g FW)^–-1 tryptamine, 103 ng · (g FW)^–-1 d-tryptophan, and 2250 ng · (g FW)^–-1 l-tryptophan. Indole-3-acetaldoxime was not found; detection limits were less than 1ng · (g FW)^–-1. When tomato shoots were incubated for 6, 10 and 21 h in 30% ^–2H₂O, up to four positions in IAA, l- and d-tryptophan, tryptamine and indole-3-pyruvate became labelled with ^–2H. Compounds became labelled rapidly with 10% of IAA molecules containing ^–2H after 6 h. The percentage of labelled molecules of IAA and l-tryptophan increased up to 10 h but then decreased again, correlating with an increase in the total shoot tryptophan and presumably a result of protein hydrolysis in the excised, slowly senescing tissue. The amount of ^–2H in d-tryptophan also showed an increase followed by a decrease, but the proportion of labelled molecules was much less than in l-tryptophan and IAA. Tryptamine became labelled initially at a similar rate to IAA but continued to accumulate ^–2H up to 21 h. We conclude that tryptamine is synthesized from a different pool of tryptophan from that used in IAA synthesis, and is not a major endogenous precursor of IAA in tomato shoots. Indole-3-pyruvate was the most heavily labelled compound after 6 and 10 h incubation (21-h data not available). Furthermore, the proportion of ^–2H-labelled indole-3-pyruvate molecules was quantitatively consistent with the amount of label in IAA. On the other hand, a quantitative comparison of the IAA turnover rate and the rate of ^–2H incorporation into both l- and d-tryptophan indicates that IAA is not made from the total shoot pool of either l- or d-tryptophan. Instead IAA appears to be synthesized from a restricted pool which is turning over rapidly and which has access to both newly synthesized tryptophan and that from protein hydrolysis.Abbreviations GC-ecd gas chromatography with electroncapture detector - GC-MS combined gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - IAOX indole-3-acetaldoxime - IPyA indole-3-pyruvate - PFB pentafluorobenzyl - R_T retention time - TNH₂ tryptamine - Trp tryptophan - SIM selected ion monitoring We wish to thank Ms. Sue Alford for running the mass spectra and Dr Harry Young for advice with the mass spectrometry. The work was supported by grants from the University of Auckland Research Committee and the C. Alma Baker Trust fund. The mass spectrometer was supported jointly by the University Grants Commitee (NZ) and the DSIR Division of Horticulture and Processing.     

H2O2 intensifies CN−-induced apoptosis in pea leaves

H2O2 intensifies CN(-)-induced apoptosis in stoma guard cells and to lesser degree in basic epidermal cells in peels of the lower epidermis isolated from pea leaves. The maximum effect of H2O2 on guard cells was observed at 10(-4) M. By switching on non-cyclic electron transfer in chloroplasts menadione and methyl viologen intensified H2O2 generation in the light, but prevented the CN--induced apoptosis in guard cells. The light stimulation of CN- effect on guard cell apoptosis cannot be caused by disturbance of the ribulose-1,5-bisphosphate carboxylase function and associated OH* generation in chloroplasts with participation of free transition metals in the Fenton or Haber-Weiss type reactions as well as with participation of the FeS clusters of the electron acceptor side of Photosystem I. Menadione and methyl viologen did not suppress the CN(-)-induced apoptosis in epidermal cells that, unlike guard cells, contain mitochondria only, but not chloroplasts. Quinacrine and diphenylene iodonium, inhibitors of NAD(P)H oxidase of cell plasma membrane, had no effect on the respiration and photosynthetic O2 evolution by leaf slices, but prevented the CN(-)-induced guard cell death. The data suggest that NAD(P)H oxidase of guard cell plasma membrane is a source of reactive oxygen species (ROS) needed for execution of CN(-)-induced programmed cell death. Chloroplasts and mitochondria were inefficient as ROS sources in the programmed death of guard cells. When ROS generation is insufficient, exogenous H2O2 exhibits a stimulating effect on programmed cell death. H2O2 decreased the inhibitory effects of DCMU and DNP-INT on the CN(-)-induced apoptosis of guard cells. Quinacrine, DCMU, and DNP-INT had no effect on CN(-)-induced death of epidermal cells.     

Endothelial NO and O2− production rates differentially regulate oxidative,nitroxidative, and nitrosative stress in the microcirculation

Endothelial dysfunction causes an imbalance in endothelial NO and O₂⁻ production rates and increased peroxynitrite formation. Peroxynitrite and its decomposition products cause multiple deleterious effects including tyrosine nitration of proteins, superoxide dismutase (SOD) inactivation, and tissue damage. Studies have shown that peroxynitrite formation during endothelial dysfunction is strongly dependent on the NO and O₂⁻ production rates. Previous experimental and modeling studies examining the role of NO and O₂⁻ production imbalance on peroxynitrite formation showed different results in biological and synthetic systems. However, there is a lack of quantitative information about the formation and biological relevance of peroxynitrite under oxidative, nitroxidative, and nitrosative stress conditions in the microcirculation. We developed a computational biotransport model to examine the role of endothelial NO and O₂⁻ production on the complex biochemical NO and O₂⁻ interactions in the microcirculation. We also modeled the effect of variability in SOD expression and activity during oxidative stress. The results showed that peroxynitrite concentration increased with increase in either O₂⁻ to NO or NO to O₂⁻ production rate ratio (Q_O2⁻/Q_NO or Q_NO/Q_O2⁻, respectively). The peroxynitrite concentrations were similar for both production rate ratios, indicating that peroxynitrite-related nitroxidative and nitrosative stresses may be similar in endothelial dysfunction or inducible NO synthase (iNOS)-induced NO production. The endothelial peroxynitrite concentration increased with increase in both Q_O2⁻/Q_NO and Q_NO/Q_O2⁻ ratios at SOD concentrations of 0.1–100 μM. The absence of SOD may not mitigate the extent of peroxynitrite-mediated toxicity, as we predicted an insignificant increase in peroxynitrite levels beyond Q_O2⁻/Q_NO and Q_NO/Q_O2⁻ ratios of 1. The results support the experimental observations of biological systems and show that peroxynitrite formation increases with increase in either NO or O₂⁻ production, and excess NO production from iNOS or from NO donors during oxidative stress conditions does not reduce the extent of peroxynitrite mediated toxicity.     

PIKfyve-dependent regulation of the Cl− channel ClC-2

The widely expressed chloride channel ClC-2 is stimulated by the serum and glucocorticoid inducible kinase SGK1. The SGK1-dependent regulation of several carriers involves the mammalian phosphatidylinositol-3-phosphate-5-kinase PIKfyve (PIP5K3). The present experiments explored whether SGK1-dependent regulation of ClC-2 similarly involves PIKfyve. The conductance of Xenopus oocytes is increased more than eightfold by ClC-2 expression. In ClC-2-expressing oocytes, but not in water-injected oocytes, the current was further enhanced by coexpression of either, PIKfyve or constitutively active ^S422DSGK1. Coexpression of the inactive SGK1 mutant ^K127NSGK1 did not significantly alter the current in ClC-2-expressing oocytes and abrogated the stimulation of the current by PIKfyve-coexpression. The stimulating effect of PIKfyve was abolished by replacement of the serine with alanine in the SGK1 consensus sequence (^S318APIKfyve). Coexpression of ^S318APIKfyve significantly blunted the stimulating effect of ^S422DSGK1 on ClC-2-activity. In conclusion, PIKfyve is a potent stimulator of ClC-2-activity and contributes to SGK1-dependent regulation of ClC-2.     

Therapeutic antibodies and infectious diseases,Tours, France,November 20−22, 2012

The Therapeutic Antibodies and Infectious Diseases international congress was held in Tours, France on November 20−22, 2012. The first session was devoted to the development of antibodies directed against bacterial toxins or viruses that could be used in a potential bioterrorist threat situation. The second session dealt with the effector functions of anti-microbial antibodies, while the third was oriented toward anti-viral antibodies, with a special emphasis on antibodies directed against the human immunodeficiency and hepatitis C viruses. After a lecture by a speaker from the US Food and Drug Administration on antibody cocktails, the second day ended with a special session dedicated to discussions regarding the involvement of French biotechnology industries in the field. On the last day, the congress concluded with talks about current antibody treatments for infectious diseases, with a particular focus on their adverse events. Participants enjoyed this very stimulating and convivial meeting, which gathered scientists from various countries who had different scientific research interests.     

Methadone but not Morphine Inhibits Lubiprostone-Stimulated Cl− Currents in T84 Intestinal Cells and Recombinant Human ClC-2, but not CFTR Cl− Currents

In clinical trials, methadone, but not morphine, appeared to prevent beneficial effects of lubiprostone, a ClC-2 Cl^? channel activator, on opioid-induced constipation. Effects of methadone and morphine on lubiprostone-stimulated Cl^? currents were measured by short circuit current (Isc) across T84 cells. Whole cell patch clamp of human ClC-2 (hClC-2) stably expressed in HEK293 cells and in a high expression cell line (HEK293EBNA) as well as human CFTR (hCFTR) stably expressed in HEK293 cells was used to study methadone and morphine effects on recombinant hClC-2 and hCFTR Cl^? currents. Methadone but not morphine inhibited lubiprostone-stimulated Isc in T84 cells with half-maximal inhibition at 100 nM. Naloxone did not affect lubiprostone stimulation or methadone inhibition of Isc. Lubiprostone-stimulated Cl^? currents in hClC-2/HEK293 cells, but not forskolin/IBMX-stimulated Cl^? currents in hCFTR/HEK293 cells, were inhibited by methadone, but not morphine. HEK293EBNA cells expressing hClC-2 showed time-dependent, voltage-activated, CdCl₂-inhibited Cl^? currents in the absence (control) and the presence of lubiprostone. Methadone, but not morphine, inhibited control and lubiprostone-stimulated hClC-2 Cl^? currents with half-maximal inhibition at 100 and 200–230 nM, respectively. Forskolin/IBMX-stimulated hClC-2 Cl^? currents were also inhibited by methadone. Myristoylated protein kinase inhibitor (a specific PKA inhibitor) inhibited forskolin/IBMX- but not lubiprostone-stimulated hClC-2 Cl^? currents. Methadone caused greater inhibition of lubiprostone-stimulated currents added before patching (66.1 %) compared with after patching (28.7 %). Methadone caused inhibition of lubiprostone-stimulated Cl^? currents in T84 cells and control; lubiprostone- and forskolin/IBMX-stimulated recombinant hClC-2 Cl^? currents may be the basis for reduced efficacy of lubiprostone in methadone-treated patients.     

Association between tumor necrosis factor-α promoter −308 A/G, −238 A/G, interleukin-6 −174 G/C and −572 G/C polymorphisms and periodontal disease: a meta-analysis

The aim of this study was to determine whether tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) promoter polymorphisms confer susceptibility to periodontitis in ethnically different populations. A literature search was performed using PubMed and Embase and a meta-analysis of the identified studies was conducted to explore the associations between TNF-α ?308 A/G, ?238 A/G, IL-6 promoter ?174 G/C and ?572 G/C polymorphisms and periodontitis. Seventeen comparison studies for the TNF-α ?308 A/G polymorphism and three studies for the TNF-α ?238 A/G polymorphism were included in the meta-analysis. And 16 separate studies for the IL-6 ?174 G/C polymorphism and 10 studies for the IL-6 ?572 G/C polymorphism were considered in our meta-analysis. Analysis after stratification by ethnicity indicated that the TNF-α ?308 A allele was associated with periodontitis in Brazilian, Asian, and Turkish populations (OR = 0.637, 95 % CI = 0.447–0.907, p = 0.013; OR = 0.403, 95 % CI = 0.204–0.707, p = 0.009; OR = 1.818, 95;  % CI = 1.036–3.189, p = 0.037). The meta-analysis showed no association between the TNF-α ?238 A/G polymorphism and periodontitis. The meta-analysis indicated an association of the IL-6 ?174 G/C polymorphisms with periodontitis in Brazilian populations (OR for GG + GC = 2.394, 95 % CI = 1.081–5.302, p = 0.031). Stratification by ethnicity and disease type indicated an association between the IL-6 ?572 G allele and chronic periodontitis (OR = 1.585, 95 % CI = 1.030–2.439, p = 0.036), and periodontitis in Europeans (OR = 2.118, 95 % CI = 1.254–3.577, p = 0.005). This meta-analysis demonstrates that the TNF-α ?308 A/G polymorphism confers susceptibility to periodontitis in Brazilian, Asian and Turkish populations. The IL-6 ?174 G/C polymorphism may confer susceptibility to periodontitis in Brazilians, and the IL-6 ?572 G/C polymorphism may be associated with susceptibility to periodontitis in Europeans, and chronic periodontitis.     

The Ca2+-inactivated Cl− Channel at Work: Selectivity,Blocker Kinetics and Transport Visualization

Removal of extracellular divalent cations activated a Cl⁻ channel in the plasma membrane of Xenopus laevis oocytes. This so-called Ca²⁺-inactivated Cl⁻ channel (CaIC) was present in every oocyte and was investigated using two-electrode whole-cell voltage clamp and single-channel patch-clamp techniques. Beside other Cl⁻ channel inhibitors, anthracene-9-carboxylic acid (9-AC) and 3′azido-3′deoxythymidine (AZT), a nucleoside analogue commonly used as an antiviral drug, blocked at least partly the CalC-mediated currents. Using the Cl⁻-sensitive dye 6-methoxy-N-(sulfopropyl)quinolinium (SPQ) we could visualize the transport of Cl⁻ from the oocyte cytoplasm to the surrounding medium after activation of the CaIC by Ca²⁺ removal. In the absence of external Cl⁻ and Ca²⁺, the emission intensity of SPQ declined continuously, indicating a quenching of fluorescence by the efflux of Cl⁻ in the millimolar range. In the presence of external Ca²⁺, no emission changes could be observed during the same time period. Chelating external Ca²⁺ in absence of Cl⁻ immediately activated Ca²⁺-inactivated Cl⁻ channels leading to subsequent emission decrease of SPQ. Investigations on the selectivity of the CaIC revealed only poor discrimination between different anions. With single-channel measurements, we found an anion selectivity sequence I⁻ > Br⁻ > Cl⁻≫ gluconate as it is also typical for maxi Cl⁻ channels. Contrary to the majority of all other transport systems of the Xenopus oocyte, which show reduced activity due to membrane depolarization or endocytotic removal of the transport protein from the plasma membrane during oocyte maturation, the CaIC remained active in maturated oocytes. Single-channel measurements on maturated oocytes, also known as eggs, showed the presence of Ca²⁺-inactivated Cl⁻ channels. However, this egg CaIC revealed an altered sensitivity to external Ca²⁺ concentrations. All these data confirm and extend our previous observations on the CaIC and give clear evidence that this channel is peculiar among all Cl⁻ channels described up to now. Received: 16 May 1996/Revised: 4 September 1996     

Separate,Ca2+-activated K+ and Cl− transport pathways in Ehrlich ascites tumor cells

Summary The net loss of KCl observed in Ehrlich ascites cells during regulatory volume decrease (RVD) following hypotonic exposure involves activation of separate conductive K⁺ and Cl^– transport pathways. RVD is accelerated when a parallel K⁺ transport pathway is provided by addition of gramicidin, indicating that the K⁺ conductance is rate limiting. Addition of ionophore A23187 plus Ca²⁺ also activates separate K⁺ and Cl^– transport pathways, resulting in a hyperpolarization of the cell membrane. A calculation shows that the K⁺ and Cl^– conductance is increased 14-and 10-fold, respectively. Gramicidin fails to accelerate the A23187-induced cell shrinkage, indicating that the Cl^– conductance is rate limiting. An A23187-induced activation of⁴²K and³⁶Cl tracer fluxes is directly demonstrated. RVD and the A23187-induced cell shrinkage both are: (i) inhibited by quinine which blocks the Ca²⁺-activated K⁺ channel. (ii) unaffected by substitution of NO ₃ ^– or SCN^– for Cl^–, and (iii) inhibited by the anti-calmodulin drug pimozide. When the K⁺ channel is blocked by quinine but bypassed by addition of gramicidin, the rate of cell shrinkage can be used to monitor the Cl^– conductance. The Cl^– conductance is increased about 60-fold during RVD. The volume-induced activation of the Cl^– transport pathway is transient, with inactivation within about 10 min. The activation induced by ionophore A23187 in Ca²⁺-free media (probably by release of Ca²⁺ from internal stores) is also transient, whereas the activation is persistent in Ca²⁺-containing media. In the latter case, addition of excess EGTA is followed by inactivation of the Cl^– transport pathway. These findings suggest that a transient increase in free cytosolic Ca²⁺ may account for the transient activation of the Cl^– transport pathway. The activated anion transport pathway is unselective, carrying both Cl^–, Br^–, NO ₃ ^– , and SCN^–. The anti-calmodulin drug pimozide blocks the volume- or A23187-induced Cl^– transport pathway and also blocks the activation of the K⁺ transport pathway. This is demonstrated directly by⁴²K flux experiments and indirectly in media where the dominating anion (SCN^–) has a high ground permeability. A comparison of the A23187-induced K⁺ conductance estimated from⁴²K flux measurements at high external K⁺, and from net K^– flux measurements suggests single-file behavior of the Ca²⁺-activated K⁺ channel. The number of Ca²⁺-activated K⁺ channels is estimated at about 100 per cell.     

NO3 −/NO2 − assimilation in halophilic archaea: physiological analysis, nasA and nasD expressions

The haloarchaeon Haloferax mediterranei is able to assimilate nitrate or nitrite using the assimilatory nitrate pathway. An assimilatory nitrate reductase (Nas) and an assimilatory nitrite reductase (NiR) catalyze the first and second reactions, respectively. The genes involved in this process are transcribed as two messengers, one polycistronic (nasABC; nasA encodes Nas) and one monocistronic (nasD; codes for NiR). Here we report the Hfx mediterranei growth as well as the Nas and NiR activities in presence of high nitrate, nitrite and salt concentrations, using different approaches such as physiological experiments and enzymatic activities assays. The nasA and nasD expression profiles are also analysed by real-time quantitative PCR. The results presented reveal that the assimilatory nitrate/nitrite pathway in Hfx mediterranei takes place even if the salt concentration is higher than those usually present in the environments where this microorganism inhabits. This haloarchaeon grows in presence of 2 M nitrate or 50 mM nitrite, which are the highest nitrate and nitrite concentrations described from a prokaryotic microorganism. Therefore, it could be attractive for bioremediation applications in sewage plants where high salt, nitrate and nitrite concentrations are detected in wastewaters and brines.     

Chemiluminescent reactions of Ru(2, 2′-bipyridine)31+,3+ and Mo6Cl141−,3−

A number of new chemiluminescent reactions are reported. These include the reaction of Mo₆Cl₁₄^1- and Mo₆Cl₁₄^3- with solvent acetonitrile, of the latter species with Ru(bipyr)₃³⁺ (bipyr=2,2′-bipyridine) and of Ru(bipyr)₃⁺ and Ru(bipyr)₃³⁺ with solvent acetonitrile and with various oxidants and reductants. Approximate chemiluminescence yields and kinetics are also reported for the reduction of acidic aqueous solutions of Ru(bipyr)₃³⁺ by luminol, SnCl₂, SO₃^2-, H₂O₂, ethylenediaminetetracetic acid, N₃^-, ethanol, Pt(CN)₄^2-, Fe(CN)₆^4- and W(CN)₈^4-.