Aquatic ecosystem as a bioreactor: water purification and some other functions.

A fundamental concept is proposed of aquatic ecosystem as a bioreactor that carries out the function of water purification in natural water bodies and streams. The ecosystem as a bioreactor has the following characteristic attributes: (1) it is a large-scale (large-volume) bioreactor; (2) it is a diversified (in terms of the number of taxa and the scope of functional activities) bioreactor; (3) it possesses a broad range of biocatalytic (chemical-transforming and degrading) capabilities. New experimental data on xenobiotics-induced inhibition of the functioning of the molluscs Unio tu- midus, U. pictorum, M. galloprovincialis and Limnaea stagnalis emphasize the potential ecological hazard from sublethal concentrations of pollutants (including those exemplified by synthetic surfactants and detergents).     

Studying effects of some surfactants and detergents on filter-feeding bivalves

Effects of several surfactants and chemical mixtures on marine bivalves were studied. An anionic surfactant, sodium dodecylsulphate (SDS), and a cationic surfactant, tetradecyltrimethylammonium bromide (TDTMA), inhibited the filtering activity of oysters (Crassostrea gigas). Similar effects were exhibited by some chemical mixtures that included surfactants. Those mixtures inhibited the filtering activity of Crassostrea gigas and Mytilus galloprovincialis. The new results are in agreement with the author's previous experiments, where a number of xenobiotics and/or pollutants inhibited the filtering activity of several species of marine and freshwater bivalves, e.g., it had been shown that SDS inhibited filtering activity of Mytilus edulis (e.g., Ostroumov, 2000c, 2001a). This experimental approach is helpful in assessment of environmental hazards from man-made chemicals that can contaminate marine systems.     

Multiple, distributed interactions of μ-conotoxin PIIIA associated with broad targeting among voltage-gated sodium channels

The first μ-conotoxin studied, μCTX GIIIA, preferentially blocked voltage-gated skeletal muscle sodium channels, Na(v)1.4, while μCTX PIIIA was the first to show significant blocking action against neuronal voltage-gated sodium channels. PIIIA shares >60% sequence identity with the well-studied GIIIA, and both toxins preferentially block the skeletal muscle sodium channel isoform. Two important features of blocking by wild-type GIIIA are the toxin's high binding affinity and the completeness of block of a single channel by a bound toxin molecule. With GIIIA, neutral replacement of the critical residue, Arg-13, allows a residual single-channel current (~30% of the unblocked, unitary amplitude) when the mutant toxin is bound to the channel and reduces the binding affinity of the toxin for Na(v)1.4 (~100-fold) [Becker, S., et al. (1992) Biochemistry 31, 8229-8238]. The homologous residue in PIIIA, Arg-14, is also essential for completeness of block but less important in the toxin's binding affinity (~55% residual current and ~11-fold decrease in affinity when substituted with alanine or glutamine). The weakened dominance of this key arginine in PIIIA is also seen in the fact that there is not just one (R13 in GIIIA) but three basic residues (R12, R14, and K17) for which individual neutral replacement enables a substantial residual current through the bound channel. We suggest that, despite a high degree of sequence conservation between GIIIA and PIIIA, the weaker dependence of PIIIA's action on its key arginine and the presence of a nonconserved histidine near the C-terminus may contribute to the greater promiscuity of its interactions with different sodium channel isoforms.     

Characterization of fluorescent chlorophyll charge-transfer states as intermediates in the excited state quenching of light-harvesting complex II

Photosynthesis Research - Light-harvesting complex II (LHCII) is the major antenna complex in higher plants and green algae. It has been suggested that a major part of the excited state energy...     

Study of hydrocarbon oxidizing microorganisms from deep groundwater of the Puchezh-Katunki impact structure

The presence of viable hydrocarbon-oxidizing microorganisms has been shown in the under-ground waters exposed by the Vorotilovskaya deep well (the Puchezh-Katunki astrobleme, 75 km north of Nizhny Novgorod, 1900- and 3200-m deep) using the method of chromatography-mass spectrometry of specific biomarkers of the microbial cell wall and the classical methods of bacteriology. Several microbial species have been isolated in pure culture and identified. Two bacillary species, Bacillus pumilus KTB-2 and Bacillus subtilis KTB-4, were maintained in pure cultures at reinoculations. The effects of mineralization and aeration of the medium on the growth characteristics of Bacillus pumilus KTB-2 in batch culture have been studied.     

Cystic fibrosis transmembrane conductance regulator modulates synaptic chloride homeostasis in motoneurons of the rat spinal cord during neonatal development

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-regulated Cl(-) channel functional in neonatal rat spinal motoneurons. The present study investigated the developmental (P1-P8) expression of CFTR, its impact on motoneuron excitability and Cl(-) homeostasis in relation to canonical Cl(-) transporters. The Cl(-) outward transporter KCC2 gene was upregulated in females over males and increased from P1 to P8. The gene activities of the Cl(-) inward transporter NKCC1 and CFTR were positively correlated and grew between P1 and P8. P1 motoneuronal somata were immunopositive for CFTR whose expression later (P8) extended to cell processes. KCC2 immunopositivity outlined somata and cell processes at P1 and P8. Electrophysiological recording with sharp electrodes showed that the CFTR blocker glibenclamide increased motoneuron input resistance, suggesting functional CFTR in P1-P8 motoneurons. Whole cell patch-clamping of spinal motoneurons to study CFTR contribution to postnatal synaptic Cl(-) regulation indicated that glibenclamide or the selective CFTR blocker diphenylamine-2,2'-dicarboxylic acid produced a negative shift in GABA/glycine reversal potential (E(GABA/Gly) ) of spontaneously occurring synaptic events measured after block of excitatory transmission. A similar effect on E(GABA/Gly) was induced by the NKCC1 inhibitor bumetanide. A 3D reconstructed motoneuron model suggested that CFTR activity contributes to set the E(GABA/Gly) positive to the resting potential. The functional outcome of these Cl(-) mediated synaptic events depended not only on the postnatal age of the animal but also on their timing with respect to the excitatory synaptic signals. We propose that CFTR operated together with NKCC1 to produce depolarizing GABA/glycine mediated synaptic events.