Water column anammox and denitrification in a temperate permanently stratified lake (Lake Rassnitzer,Germany)

We studied microbial N₂ production via anammox and denitrification in the anoxic water column of a restored mining pit lake in Germany over an annual cycle. We obtained high-resolution hydrochemical profiles using a continuous pumping sampler. Lake Rassnitzer is permanently stratified at ca. 29 m depth, entraining anoxic water below a saline density gradient. Mixed-layer nitrate concentrations averaged ca. 200 μmol L⁻¹, but decreased to zero in the anoxic bottom waters. In contrast, ammonium was <5 μmol L⁻¹ in the mixed layer but increased in the anoxic waters to ca. 600 μmol L⁻¹ near the sediments. In January and October, ¹⁵N tracer measurements detected anammox activity (maximum 504 nmol N₂ L⁻¹ d⁻¹ in ¹⁵NH₄⁺-amended incubations), but no denitrification. In contrast, in May, N₂ production was dominated by denitrification (maximum 74 nmol N₂ L⁻¹ d⁻¹). Anammox activity in May was significantly lower than in October, as characterized by anammox rates (maximum 6 vs. 16 nmol N₂ L⁻¹ d⁻¹ in incubations with ¹⁵NO₃⁻), as well as relative and absolute anammox bacterial cell abundances (0.56% vs. 0.98% of all bacteria, and 2.7×10⁴ vs. 5.2×10⁴ anammox cells mL⁻¹, respectively) (quantified by catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) with anammox bacteria-specific probes). Anammox bacterial diversity was investigated with anammox bacteria-specific 16S rRNA gene clone libraries. The majority of anammox bacterial sequences were related to the widespread Candidatus Scalindua sorokinii/brodae cluster. However, we also found sequences related to Candidatus S. wagneri and Candidatus Brocadia fulgida, which suggests a high anammox bacterial diversity in this lake comparable with estuarine sediments.     

Ecology of aquatic Ranunculus communities under the Mediterranean climate

The Iberian Peninsula encompasses more than 80% of the species richness of European aquatic ranunculi. The floristic diversity of the phytocoenosis characterised by aquatic Ranunculus and the main physical–chemical factors of the water were studied in 43 localities of the central Iberian Peninsula. Four aquatic Ranunculus communities are found in most of the aquatic environments. These are species-poor and have an uneven distribution: three species of Batrachium are heterophyllous and their communities are distributed in different aquatic ecosystems on silicated substrates; one species is homophyllous and its community occurs in various aquatic ecosystems with carbonated waters. In the Mediterranean climate, Ranunculus species are present in different habitats, as shown by the results of all the statistical analyses. Ranunculus trichophyllus communities occur in base-rich waters with a high buffering capacity (2273.44 ± 794.57 mg CaCO₃ L⁻¹) and a high concentration of cations (Ca²⁺, 121 ± 33.12 mg L⁻¹; Mg²⁺, 71.64 ± 82.77 mg L⁻¹), nitrates (2.89 ± 4.80 mg L⁻¹), ammonium (2.19 ± 1.36 mg L⁻¹) and sulphates (216.25 ± 218.54 mg L⁻¹). Ranunculus penicillatus communities are found in flowing waters with a high concentration of phosphates (0.48 ± 0.6 mg L⁻¹) and intermediate buffering capacity (683.66 ± 446.76 mg CaCO₃ L⁻¹). Both Ranunculus pseudofluitans and Ranunculus peltatus communities grow in waters with low buffering capacity (R. pseudofluitans, 385.91 ± 209.2 mg CaCO₃ L⁻¹; R. peltatus, 263.3 ± 180.36 mg CaCO₃ L⁻¹), and a low concentration of cations (R. pseudofluitans: Ca²⁺, 12.57 ± 9.42 mg L⁻¹; Mg²⁺, 3.42 ± 1.67 mg L⁻¹; R. peltatus: Ca²⁺, 15 ± 18.26 mg L⁻¹; Mg²⁺, 6.26 ± 8.89 mg L⁻¹) and nutrients (R. pseudofluitans: nitrates, 0.23 ± 0.2 mg L⁻¹; phosphates, 0.09 ± 0.1 mg L⁻¹; R. peltatus: nitrates, 0.19 ± 0.21 mg L⁻¹; phosphates, 0.09 ± 0.12 mg L⁻¹); the first in flowing waters, the latter in still waters.     

Performance of a submerged membrane bioreactor for the aerobic treatment of abattoir wastewater

The performance of a submerged membrane bioreactor (SMBR) has been investigated for abattoir wastewater (AW) treatment. The chemical oxygen demand (COD) of permeate has not exceeded 25 mg L⁻¹ providing an average COD removal of 98%. Microbiological analysis showed that the SMBR has allowed a complete removal of fecal coliforms, Listeria and Salmonella. A significant reduction in the excess biomass production was also observed. In fact, the yield of biomass production (Yobs) ranged between 0 and 0.106 g suspended solids/g COD removed.The study of the dynamic of bacterial communities using the single strand conformation polymorphism (SSCP) method showed a significant change in the population structure and revealed a correlation between the sludge production yield and the bacterial communities.     

Investigation of the optimal carbon-nitrogen ratio and carbohydrate-nutrient blend for mixed-acid batch fermentations

To determine the optimal scenario for mixed-acid fermentations, an array of batch fermentations were performed that independently varied the C/N ratio (adjusted using urea) and the blend of carbohydrate (office paper) and nutrient (wet chicken manure (CM)). A blend of 93% paper and 7% wet CM (dry basis) with a C/N ratio of 37 g C_NA/g N had the highest culture yield (0.21 g acid_produced/g NAVS_initial), total acid productivity (0.84 g acid_produced/(L_liq d)), and conversion (0.43 g NAVS_consumed/g NAVS_initial). Compared to a control blend of 80% paper and 20% wet CM (dry basis, no urea) the culture yield, productivity, and conversion improved 53%, 44%, and 70%, respectively. Selectivity was a strong function of C/N ratio and varied from 0.167 to 0.667 acid_produced/g NAVS_consumed. Nitrogen supplementation with urea improves performance and reduces costs of (1) capital, (2) nutrients, and (3) downstream processing by reducing impurities from nutrient-rich wastes (e.g., manures, sewage sludge).     

Effects of oxygen tension and follicle cells on maturation and fertilization of porcine oocytes during in vitro culture in follicular fluid

The objective was to investigate the effects of oxygen tension and follicle cells (FCs) during in vitro maturation of porcine oocytes in only porcine (Sus scrofa domesticus) follicular fluid (pFF), using static and non-static (rotating) culture systems, on the nuclear maturation and subsequent in vitro fertilization of the oocytes. In the first experiment, cumulus-oocyte complexes (COCs) were matured for 48 h in pFF supplemented with (+) or without (−) FCs (5.2 × 10⁶ cells/mL), using the static (S) and rotating (R) culture systems (+FC/S, −FC/S, +FC/R, and −FC/R) under 5% or 20% O₂. Co-culture with FCs in the static culture system (+FC/S) had a detrimental effect on the meiotic competence of oocytes, whereas co-culture with FCs in the rotating culture system (+FC/R) increased maturation rates. In both culture systems, oxygen tension had no apparent effects on meiotic competence of oocytes, irrespective of culture system and FC addition. In the second experiment, COCs were matured under 5% or 20% O₂ using the −FC/S or +FC/R culture systems and then fertilized. Oxygen tension had no significant effects on fertilization parameters, irrespective of the culture system. The rotating culture system increased rates of sperm penetration and male pronuclear formation and decreased polyspermic fertilization compared with the static culture system (P < 0.05). In conclusion, both −FC/S and +FC/R culture systems supported meiotic competence, irrespective of oxygen tension. However, the +FC/R culture system may be superior to the −FC/S culture system for promoting fertilization.     

Ethanol production from syngas by Clostridium strain P11 using corn steep liquor as a nutrient replacement to yeast extract

The feasibility of replacing yeast extract (YE) by corn steep liquor (CSL), a low cost nutrient source, for syngas fermentation to produce ethanol using Clostridium strain P11 was investigated. About 32% more ethanol (1.7 g L⁻¹) was produced with 20 g L⁻¹ CSL media in 250-mL bottle fermentations compared to media with 1 g L⁻¹ YE after 360 h. Maximum ethanol concentrations after 360 h of fermentation in a 7.5-L fermentor with 10 and 20 g L⁻¹ CSL media were 8.6 and 9.6 g L⁻¹, respectively, which represent 57% and 60% of the theoretical ethanol yields from CO. Only about 6.1 g L⁻¹ of ethanol was obtained in the medium with 1 g L⁻¹ YE after 360 h, which represents 53% of the theoretical ethanol yield from CO. The use of CSL also enhanced butanol production by sevenfold compared to YE in bottle fermentations. These results demonstrate that CSL can replace YE as the primary medium component and significantly enhance ethanol production by Clostridium strain P11.     

Performance evaluation and phylogenetic characterization of anaerobic fluidized bed reactors using ground tire and pet as support materials for biohydrogen production

This study evaluated two different support materials (ground tire and polyethylene terephthalate [PET]) for biohydrogen production in an anaerobic fluidized bed reactor (AFBR) treating synthetic wastewater containing glucose (4000 mg L⁻¹). The AFBR, which contained either ground tire (R1) or PET (R2) as support materials, were inoculated with thermally pretreated anaerobic sludge and operated at a temperature of 30 °C. The AFBR were operated with a range of hydraulic retention times (HRT) between 1 and 8 h. The reactor R1 operating with a HRT of 2 h showed better performance than reactor R2, reaching a maximum hydrogen yield of 2.25 mol H₂ mol⁻¹ glucose with 1.3 mg of biomass (as the total volatile solids) attached to each gram of ground tire. Subsequent 16S rRNA gene sequencing and phylogenetic analysis of particle samples revealed that reactor R1 favored the presence of hydrogen-producing bacteria such as Clostridium, Bacillus, and Enterobacter.     

Oxygen consumption,ventilation frequency and cytochrome c oxidase activity in blue cod (Parapercis colias) exposed to hydrogen sulphide or isoeugenol

The effects of hydrogen sulphide (H₂S) and isoeugenol exposure on activity, oxygen consumption (VO₂), ventilation frequency (Vf) and cytochrome c oxidase activity in a teleost fish are reported. In H₂S (200 µM Na₂S) exposed animals VO₂ and Vf decreased significantly (both to 40% of resting) after 30 min, concurrent with a loss of equilibrium and narcosis. Post-flushing, VO₂ increased to resting values, but Vf remained depressed (P < 0.05) until 30 min of recovery. Subsequently, equilibrium and mobility were regained accompanied by increases in VO₂ (66%) and Vf (15%) between 60–70 min of recovery. Isoeugenol (0.011 g L^− 1) exposed fish reached stage 4–5 of anaesthesia accompanied by decreases (P < 0.05) in VO₂ (64%) and Vf (38%) by 35 min. Post-flushing, VO₂ and Vf recovered to resting values, followed by a rise (P < 0.05) in VO₂ (45%) and Vf (25%). Overall, VO₂ in relation to the resting rate was reduced in isoeugenol treated animals. Conversely, VO₂ was increased (P < 0.05) relative to the resting rate in H₂S exposed fish. 20 and 200 µM Na₂S reduced cytochrome c oxidase activity (P < 0.05) in skeletal muscle and gill lamellae by between 69 and 97%, while isoeugenol had no effect in any tissue.     

The effects of intertidal air exposure on the respiratory physiology and the killing activity of hemocytes in the pacific oyster, Crassostrea gigas (Thunberg)

The occurrence of summer mortalities of the commercially important Pacific oyster, Crassostrea gigas, has increased in recent years. These mortality events occur during the late summer when water temperatures are at their highest. Many theories have been proposed concerning the causes including reproductive stress, environmental stress, disease, or synergistic interactions of these factors. C. gigas are grown intertidally and are exposed to the air (emersed) for hours at a time. These organisms can experience extreme changes in temperature during the course of a day. An oyster closed during emersion depletes the oxygen stores to near zero within the shell and builds up CO₂ causing a decrease in tissue pH. The focus of this study is to determine the respiratory (pH, Po₂, Pco₂ and total CO₂) and immune responses of oysters exposed to air at normal seasonal temperatures, and to determine whether these stresses associated with emersion inhibit the immune system of the oyster and contribute to the summer mortalities. The respiratory variables of the hemolymph of oysters submerged at 18 °C (pH = 7.52 ± 0.04 S.E.M., Po₂ = 7.09 ± 0.53 S.E.M. kPa and Pco₂ = 0.20 ± 0.03 S.E.M. kPa) varied significantly from oysters emersed for four hours at 22°C (pH = 7.11 ± 0.03 S.E.M., Po₂ = 3.83 ± 0.15 S.E.M. kPa, Pco₂ = 0.36 ± 0.03 S.E.M. kPa) and those emersed for four hours at 30 °C (pH = 6.84 ± 0.02 S.E.M., Po₂ = 3.10 ± 0.12 S.E.M. kPa, Pco₂ = 1.31 ± 0.06 S.E.M. kPa). The ability of hemocytes to kill the bacterium Vibrio campbellii was assessed using an in vitro assay to generate a killing index. There was no significant difference in the killing index between pH treatment groups (p = 0.856): at pH 7.6 killing index = 50.2% ± 2.33 S.E.M., at pH 6.6 killing index = 52.3% ± 3.67 S.E.M.. Temperature was the only factor to significantly affect the killing indices among temperature and oxygen treatment groups. The killing index was lowest (29.3% ± 3.25 S.E.M.) at 30 °C and 7% oxygen, simulating in vivo oxygen pressure in well-aerated conditions and 30 °C and 3% oxygen, simulating in vivo oxygen pressure in hypoxia (30.5% ± 3.25 S.E.M.), compared with the index in 7% oxygen at low temperature (18 °C) (44.4% ± 4.50 S.E.M.) or compared with low oxygen (3%) at low temperature (18 °C) (39.7% ± 2.51 S.E.M.). The seasonal and diurnal rise in temperature may, therefore, be an important factor contributing to summer mortalities of C. gigas.     

Application of targeted metagenomics to explore abundance and diversity of CO2-fixing bacterial community using cbbL gene from the rhizosphere of Arachis hypogaea

Sequestration of CO₂ by autotrophic bacteria is a key process of biogeochemical carbon cycling in soil ecosystem. Rhizosphere is a rich niche of microbial activity and diversity, influenced by change in atmospheric CO₂. Structural changes in rhizosphere composition influence microbial communities and the nutrient cycling. In the present study, the bacterial diversity and population dynamics were established using cbbL and 16S rRNA gene targeted metagenomics approach from the rhizosphere of Arachis hypogaea. A total of 108 cbbL clones were obtained from the rhizospheric soil which revealed predominance of cbbL sequences affiliated to Rhizobium leguminosarum, Bradyrhizobium sp., Sinorhizobium meliloti, Ochrobactrum anthropi and a variety of uncultured cbbL harboring bacteria. The 16S rRNA gene clone library exhibited the dominance of Firmicutes (34.4%), Proteobacteria (18.3%), Actinobacteria (17.2%) and Bacteroidetes (16.1%). About 43% nucleotide sequences of 16S rRNA gene clone library were novel genera which showed < 95% homology with published sequences. Gene copy number of cbbL and 16S rRNA genes, determined by quantitative real‐time PCR (qRT PCR), was 9.38 ± 0.75 × 10⁷ and 5.43 ± 0.79 × 10⁸ (per g dry soil), respectively. The results exhibited bacterial community structure with high bacterial diversity and abundance of CO₂‐fixing bacteria, which can be explored further for their role in carbon cycling, sustainable agriculture and environment management.     

An antiferromagnetically coupled trinuclear Cu(II) complex containing μ(O,O′), μ(O) carboxylates and μ(O) phenoxide bridges

The trinuclear complex [L₂Cu₃(CF₃CO₂)₄] (1) has been synthesized and its crystal structure determined. It consists of a linear arrangement of Cu(II) centers. The central copper atom is bonded to six oxygen atoms and has a tetragonally distorted octahedral geometry, while the terminal copper atoms are bonded to three oxygen and two nitrogen atoms and show a distorted square pyramidal geometry. The complex shows di-μ(O,O′) syn-syn carboxylate bridging as well as monoatomic (μ-O) bridging, along with phenolate (μ-O) oxygen bridging. Cryomagnetic investigations in the range 2-300 K revealed an antiferromagnetic spin exchange interaction with J = −95.7 cm⁻¹, based on the isotropic exchange model H_ex = −2J[S₁ · S₂ + S₂ · S₃].     

Synthesis, structures, electrochemistry and properties of dioxo-molybdenum(VI) and -tungsten(VI) complexes with novel asymmetric N2OS, and partially symmetric N2S2, NOS2N-capped tripodal ligands

A new class of asymmetric N-capped (dianionic/trianionic) tripodal proligands [H_x(Lⁿ)] (x = 2, n = 1-6; x = 3, n = 7, 8) which possess pendant arms with N₂OS, N₂S₂ or NOS₂ donor groups and with different chelate ring sizes {5,5,5} or {5,6,5} has been prepared. Treatment of these ligands with [WO₂Cl₂(dme)] (dme = 1,2-dimethoxyethane) in the presence of base (triethylamine or KOH) leads to the formation of cis-dioxotungsten(VI) complexes of the types [WO₂(Lⁿ)] (n = 1-6) and K[WO₂(Lⁿ)] (n = 7, 8). Reaction of these tetradentate ligands with [MoO₂(acac)₂] (acac = acetylacetonate) gives the corresponding Mo(VI) analogues [MoO₂(Lⁿ)] (n = 1-6) and K[MoO₂(Lⁿ)] (n = 7, 8). Moreover, a new five coordinate dioxomolybdenum(VI) complex with an NS₂ tridentate ligand [MoO₂(L⁹)] has been synthesised using similar procedure. All these compounds have been spectroscopically characterised and the molecular structures of [MoO₂(Lⁿ)] (n = 2, 6) and [WO₂(L⁶)] have been established by X-ray diffraction analysis. The electrochemistry and the catalytic activity for oxidation of allylic and benzylic alcohols of these dioxo complexes have also been investigated.     

Cobalt and nickel complexes of versatile imidazole- and pyrrole-2-carbaldehyde thiosemicarbazones. Synthesis, characterisation and antimicrobial activity

Ni(II), Co(II) and Co(III) complexes of imidazole- and pyrrole-2-carbaldehyde thiosemicarbazone ligands (H₂L¹ and H₂L², respectively) have been prepared. The X-ray crystal structures of [Co(L¹)(HL¹)], [Ni(H₂L¹)₂]Cl₂ · 3.5H₂O and [Ni(HL²)₂] have been solved. The Co(III) ion assumes a slightly distorted octahedral coordination geometry, involving both N₂S binding domain of di- and monoanionic ligand molecules. Whereas in [Ni(HL²)₂] the metal ion is tetracoordinated in a square planar geometry by two pyrrole-2-carbaldehyde thiosemicarbazone molecules acting as NS-donor, the spatial array of non deprotonated H₂L¹ ligand molecules in [Ni(H₂L¹)₂]Cl₂ · 3.5H₂O is equivalent to that found for [Co(L¹)(HL¹)]. The in vitro antimicrobial properties of the ligands and their complexes were tested against representative bacterial and fungal strains in broth culture. The compounds H₂L² and [Co(L²)(HL²)(H₂L²)] · 1.5H₂O exhibit a moderate inhibitory effect on the microbial proliferation and only against some Gram positive bacteria.     

Development of an industrial ethanol-producing yeast strain for efficient utilization of cellobiose

The BGL1 gene, encoding β-glucosidase in Saccharomycopsis fibuligera, was intracellular, secreted or cell-wall associated expressed in an industrial strain of Saccharomyces cerevisiae. The obtained recombinant strains were studied under aerobic and anaerobic conditions. The results indicated that both the wild type and recombinant strain expressing intracellular β-glucosidase cannot grow in medium using cellobiose as sole carbon source. As for the recombinant EB1 expressing secreted enzyme and WB1 expressing cell-wall associated enzyme, the maximum specific growth rates (μ_max) could reach 0.03 and 0.05 h⁻¹ under anaerobic conditions, respectively. Meanwhile, the surface-engineered S. cerevisiae utilized 5.2 g cellobiose L⁻¹ and produced 2.3 g ethanol L⁻¹ in 48 h, while S. cerevisiae secreting β-glucosidase into culture broth used 3.6 g cellobiose L⁻¹ and produced 1.5 g ethanol L⁻¹ over the same period, but no-full depletion of cellobiose were observed for both the used recombinant strains. The results suggest that S. cerevisiae used in industrial ethanol production is deficient in cellobiose transporter. However, when β-glucoside permease and β-glucosidase were co-expressed in this strain, it could uptake cellobiose and showed higher growth rate (0.11 h⁻¹) on cellobiose.     

Effects of ether vs. ester linkage on lipid bilayer structure and water permeability

The structure and water permeability of bilayers composed of the ether-linked lipid, dihexadecylphosphatidylcholine (DHPC), were studied and compared with the ester-linked lipid, dipalmitoylphosphaditdylcholine (DPPC). Wide angle X-ray scattering on oriented bilayers in the fluid phase indicate that the area per lipid A is slightly larger for DHPC than for DPPC. Low angle X-ray scattering yields A = 65.1 Å² for DHPC at 48 °C. LAXS data provide the bending modulus, K_C = 4.2 × 10⁻¹³ erg, and the Hamaker parameter H = 7.2 × 10⁻¹⁴ erg for the van der Waals attractive interaction between neighboring bilayers. For the low temperature phases with ordered hydrocarbon chains, we confirm the transition from a tilted L_β′ gel phase to an untilted, interdigitated L_βI phase as the sample hydrates at 20 °C. Our measurement of water permeability, P_f = 0.022 cm/s at 48 °C for fluid phase DHPC is slightly smaller than that of DPPC (P_f = 0.027 cm/s) at 50 °C, consistent with our triple slab theory of permeability.     

Structure and luminescence of copper(I) cyanide-amine and -sulfide networks

Copper(I) cyanide reacts with various liquid amines and sulfides (L) under solvent-less conditions to form (CuCN)L_n, n = 0.5, 0.57, 0.75, 0.8, 1, 1.25, 1.5, 2. New X-ray structures are reported for L = Py (Py = pyridine, n = 0.57), 2-MePy (n = 1), 3-EtPy (n = 1.5), 2-ClPy (n = 1), 3-ClPy (n = 2), 3-MeOPy (n = 2), 4-^tBuPy (n = 1.5), piperidine (n = 1.25), N-methylmorpholine (n = 1), N,N-dimethylcyclohexylamine (n = 1), 1-methylimidazole (n = 3), Me₂S (n = 1), and tetrahydrothiophene (n = 1). The amine structures (except for the monomeric 1-methylimidazole complex) reveal 1D CuCN chains decorated with 0-2 L per metal atom. Chain structures observed include zigzag, helical and figure-8 helical. The CuCN-sulfide structures show sulfur-bridging of CuCN chains. In some cases (CuCN)L_?1.5 species are transformed to (CuCN)L under vacuum. Thermal analysis shows facile release of ligand, yielding CuCN. Most of the (CuCN)L_n products are photoluminescent, emitting in the visible region. In some cases, coordination of very similar amines results in remarkably different emission spectra.     

Synthesis, characterization and cytotoxic properties of platinum(II) complexes containing the nucleosides adenosine and cytidine

Cytidine (cyt) and adenosine (ado) react with cis-[L₂Pt(μ-OH)]₂(NO₃)₂ (L = PMe₃, PPh₃) in various solvents to give the nucleoside complexes cis-[L₂Pt{cyt(− H),N³N⁴}]₃(NO₃)₃ (L = PMe₃, 1),cis-[L₂Pt{cyt(− H),N⁴}(cyt,N³)]NO₃ (L = PPh₃, 2), cis-[L₂Pt{ado(− H),N¹N⁶}]₂(NO₃)₂ (L = PMe₃, 3) and cis-[L₂Pt{ado(− H),N⁶N⁷}]NO₃ (L = PPh₃, 4). When the condensation reaction is carried out in solution of nitriles (RCN, R = Me, Ph) the amidine derivatives cis-[(PPh₃)₂PtNH=C(R){cyt(− 2H)}]NO₃ (R = Me, 5a; R = Ph, 5b) and cis-[(PPh₃)₂PtNH=C(R){ado(− 2H)}]NO₃ (R = Me, 6a: R = Ph, 6b) are quantitatively formed. The coordination mode of these nucleosides, characterized in solution by multinuclear NMR spectroscopy and mass spectrometry, is similar to that previously observed for the nucleobases 1-methylcytosine (1-MeCy) and 9-methyladenine (9-MeAd). The cytotoxic properties of the new complexes, and those of the nucleobase analogs, cis-[(PPh₃)₂PtNH=C(R){1-MeCy(− 2H)}]NO₃ (R = Me, 7a: R = Ph, 7b), cis-[(PPh₃)₂PtNH=C(R){9-MeAd(− 2H)}]NO₃ (R = Me, 8a: R = Ph, 8b) have been investigated in a wide panel of human cancer cells. Interestingly, whereas the Pt(II) nucleoside complexes (1-4) did not show appreciable cytotoxicity, the corresponding amidine derivatives (7a, 7b, 8a, 8b, 5b, and 6b) exhibited a significant in vitro antitumor activity.     

Indole and aminoimidazole moieties appear as key structural units in antiplasmodial molecules

From a library of compounds of natural sources, a big series of molecules was chosen by random sampling to evaluate their in vitro antimalarial activity against Plasmodium falciparum and their antifungal activity against Candida sp. From 184 molecules tested, no molecules were active against Candida sp. (MIC > 10 μg/ml) whereas 13 clearly showed high antiplasmodial activity in vitro, with an IC₅₀ less than 1 μg/ml against the chloroquine-resistant strain of P. falciparum FcM29-Cameroon. The molecules with the best antiplasmodial efficacy were 10-hydroxy-ellipticin (IC₅₀: 0.08 μg/ml), tchibangensin (IC₅₀: 0.13 μg/ml), ellipticin hydrochloride (IC₅₀: 0.17 μg/ml), usambarensin (IC₅₀: 0.23 μg/ml), 7S,3S-ochropposinine oxindole (IC₅₀: 0.25 μg/ml), 3,14-dihydro-ellipticin (IC₅₀: 0.25 μg/ml), tetrahydro-4′,5′,6′17-usambarensin 17S (IC₅₀: 0.26 μg/ml), ellipticine (IC₅₀: 0.28 μg/ml), aricin (IC₅₀: 0.3 μg/ml), 10-methoxy-ellipticin (IC₅₀: 0.32 μg/ml), aplysinopsin (IC₅₀: 0.43 μg/ml), descarbomethoxydihydrogambirtannin (IC₅₀: 0.46 μg/ml) and ochrolifuanin A (IC₅₀: 0.47 μg/ml). Among these 13 promising molecules, all except descarbomethoxydihydrogambirtannin, ochrolifuanine A and usambarensine presented here novel biological activities since they had never been described in the literature for their antiplasmodial activity. In spite of the large diversity of the molecules which have been tested, it is interesting to note that the ones active against Plasmodium are all indole derivatives (and one is both indolic and aminoimidazolic). To find new antiplasmodial compounds, ethnopharmacological approaches studying traditional medicine treatments for malaria is largely used but random research produced here an interesting yield (7%) of new antiplasmodial hits and appears therefore complementary to the traditional medicine way.     

Effects of light regime and oxygen profile on transformation of oxolinic acid in pond sediment

This study investigated the effects of light (visible light - 5800 lux, 24 h) or dark regime and aerobic or anaerobic condition on the decay of added oxolinic acid (OA) at 5, 10 and 20 mg L⁻¹ in eel pond sediment. An asymptotic decaying exponential model C_t = C_min + C_o × exp (−k × t) was used to facilitate quantitative approach to OA transformation, where C_t is the concentration of OA after t days, C_min the estimated level-off concentration of OA residue, C_o the concentration of added OA and k the decaying coefficient. OA decayed faster under light (C_min = 4.6 mg L⁻¹) than under dark (C_min = 7.8 mg L⁻¹) and also decayed faster under aerobic (C_min = 4.0 mg L⁻¹) than under anaerobic condition (C_min = 8.5 mg L⁻¹). C_min increased with C_o. Sundrying and tilling eel pond bottom should be able to reduce OA residue significantly.