Removal and recovery of Cu(II) from industrial effluent by immobilized cells of Pseudomonas putida II-11

A copper [Cu(II)]-accumulating strain, Pseudomonas putida II-11, isolated from electroplating effluent removed a significantly high amount of Cu(II) from growth medium and buffer. A laboratory-scale fixed bed reactor with cells of P. putida II-11 immobilized in polyacrylamide gel was constructed. The adsorption of Cu(II) by the immobilized cells was pH-dependent. Maximum removal of Cu(II) by the immobilized cells was at pH 8.0. The presence of Cr(IV), Ni(II) and Zn(II) did not significantly inhibit Cu(II) uptake whereas the presence of Pb(II) reduced Cu(II) uptake by fivefold. The presence of borate, carbonate, chloride and sulphate did not significantly inhibit Cu(II) uptake. The Cu(II) removal capacity of the bioreactor with immobilized cells did not change significantly when operated at retention times greater than 3 min. More than 90% of Cu(II) adsorbed on immobilized cells could be recovered by eluting with 0.1 m HCl. The bioreactor could be used for at least five loading-elution cycles without loss of Cu(II) removal capacity. The feasibility of using this bioreactor to remove and recover Cu(II) from electroplating effluent is discussed. Correspondence to: P. K. Wong     

INFLUENCE OF NATURAL ULTRAVIOLET RADIATION ON LOTIC PERIPHYTIC DIATOM COMMUNITY GROWTH,BIOMASS ACCRUAL,AND SPECIES COMPOSITION: SHORT-TERM VERSUS LONG-TERM EFFECTS1, 2

Growth rates, accumulation dynamics, and species succession of periphytic diatom communities were examined in the presence and absence of natural ultraviolet (UV) radiation using a series of outdoor, continuous-flow experimental flumes located on the South Thompson River, British Columbia. In a short-term experiment (2–3 wk), log-phase growth rates of naturally seeded diatom communities comprised of Tabellaria fenestrata (Lyngb.) Kütz., T. flocculosa (Roth) Kütz., Fragilaria crotonesis Kitton, and F. vaucheriae (Ehr.) Peter. exposed to 90% ambient photosynthetically active radiation (PAR) + UV were 30–40% lower than growth rates under 90% PAR alone. UV inhibition of growth rate was independent of the degree of P limitation within the range of relative specific growth rates (μ:μ_max-P) of 0.5–1.0. In a long-term trial, inhibition of attached diatom accumulation under 90% PAR + UV during the first 2–3 wk was corroborated. Reduction of full sunlight to 50% PAR + UV prevented the initial inhibition phase. The initial inihibitory effect of 90% PAR + UV on algal accumulation was reversed after 3–4 wk, and by 5 wk total diatom abundance (chlorophyll a, cell numbers and cell biovolumes) in communities exposed to PAR + UV were 2–4-old greater than in communities protected from UV. Under 90% PAR + UV and 50% PAR + UV, a succession to stalked diatom genera (Cymbella and Gomphoneis) occurred. Species succession under UV radiation doubled the mean cell size of the diatom communities. The shift from inhibition to a long-term increase in the autotrophic community under PAR + UV compared to PAR alone provides further evidence against the use of short-term incubation experiments to define the long-term implications of increases in UVB. These results suggest that the ecological effects of present-day levels of UVB and UVB:UVA ratios on autotrophic communities are not well understood and might be mediated through complex trophic level interactions.     

Is there hybridization between diploid and tetraploid Euphrasia in a secondary contact zone?

Premise

Strong postzygotic reproductive isolating barriers are usually expected to limit the extent of natural hybridization between species with contrasting ploidy. However, genomic sequencing has revealed previously overlooked examples of natural cross-ploidy hybridization in some flowering plant genera, suggesting that the phenomenon may be more common than once thought. We investigated potential cross-ploidy hybridization in British eyebrights (Euphrasia, Orobanchaceae), a group from which 13 putative cross-ploidy hybrid combinations have been reported based on morphology.

Methods

We analyzed a contact zone between diploid Euphrasia rostkoviana and tetraploid E. arctica in Wales. We sequenced part of the internal transcribed spacer (ITS) of nuclear ribosomal DNA and used genotyping by sequencing (GBS) to look for evidence of cross-ploidy hybridization and introgression.

Results

Common variant sites in the ITS region were fixed between diploids and tetraploids, indicating a strong barrier to hybridization. Clustering analyses of 356 single-nucleotide polymorphisms (SNPs) generated using GBS clearly separated samples by ploidy and revealed strong genetic structure (F_ST = 0.44). However, the F_ST distribution across all SNPs was bimodal, indicating potential differential selection on loci between diploids and tetraploids. Demographic inference suggested potential gene flow, limited to around one or fewer migrants per generation.

Conclusions

Our results suggest that recent cross-ploidy hybridization is rare or absent in a site of secondary contact in Euphrasia. While a strong ploidy barrier prevents hybridization over ecological timescales, such hybrids may form in stable populations over evolutionary timescales, potentially allowing cross-ploidy introgression to take place.     

EVIDENCE OF DARK AVOIDANCE BY PHOTOTROPHIC PERIPHYTIC DIATOMS IN LOTIC SYSTEMS1

Short-term (24–48 h) colonization dynamics of periphytic diatoms on artificial (styrofoam) substrata were examined using fast-flushing, continuous-flow troughs located on the North Thompson River, British Columbia. Two parallel troughs, one exposed to natural light and the other completely darkened, showed significant differences in periphyton biomass, chlorophyll a, and algal taxonomic composition with 24 h. Experiments which commenced at the onset of natural darkness demonstrated that rates of algal immigration during the night were the same in both troughs. Within 2–3 h of sunrise, however, certain diatom species (most notably Hannaea arcus (Ehr.) Pair, and Diatoma tenue Ag.) selectively emigrated from the artificially darkened trough but remained in the trough exposed to natural light. More closely adhering species such as Achnanthes minutissima Kütz, also showed significant emigration from the darkened trough after light deprivation for two photoperiods. Data from adhesion, emigration, and sinking rate experiments indicate that differential egress of cells from the darkened versus the lighted environments is the result of cellular regulation of buoyancy or form resistance.     

Development of a selective pseudosubstrate-based peptide inhibitor of pp60c-src protein tyrosine kinase

Summary Using a combinatorial peptide library method, we identified YIYGSFK as an efficient and specific peptide substrate for pp60^c-src protein tyrosine kinase (PTK) [Lam et al., Int. J. Pept. Protein Res., 45 (1995) 587]. Employing YIYGSFK as a template, we synthesized and evaluated a series of pseudosubstrate-based inhibitors for pp60^c-src. We found that the efficiency of a given inhibitor was highly dependent on the specific tyrosine analog used at the phosphorylation site of the substrate. One of these pseudosubstrate inhibitors, YI(2-Nal)GSFK, selectively inhibited the kinase activity of pp60^c-src, with a K_i of 24 M. This peptide inhibitor exhibited selectivity for pp60^c-src as compared to other PTKs tested, such as c-Abl and Bcr-Abl. Our results suggest that selective inhibitors for a specific PTK can be developed when the structure of a specific and efficient small peptide substrate for this PTK can be used as a template for structure modification.Abbreviations 1-Nal l-1-naphthylalanine - 2-Nal l-2-naphthylalanine - BOP benzotriazolyl-N-oxy-tris(dimethylamino)-phosphonium hexafluorophosphate - BSA bovine serum albumin - cAPK cyclic AMP-dependent protein kinase - DIEA diisopropylethylamine - EGFR epidermal growth factor receptor - Fmoc fluorenylmethoxycarbonyl - HOBt 1-hydroxybenzotriazole - MES 2-[N-morpholino]ethanesulfonic acid - PBS phosphate-buffered salts - pCl l-p-chlorophenylalanine - pF l-p-fluorophenylalanine - PTK protein tyrosine kinase - TLC thin-layer chromatography     

Spatial and Temporal variations of mangrove fish assemblages in Martinique (French West Indies)

A study of the mangrove fish fauna in a bay of Martinique Island (French West Indies) was carried out at different seasons during two consecutive years. fishes were sampled with specific hoop-nets in the coastal areas at 8 stations.A total of 87 species was collected in the bay. Most individuals were represented by small-size specimens and juveniles. The overall species richness varied according to the stations and the sampling periods. The biomass and number of individuals were variable according to the location but remained stable in time. A factor correspondence analysis and a hierarchical clustering with median links were used to follow the evolution of the stations in space and time. Two types of stations were differentiated: the stations characterized by the mangrove and those under the influence of seagrass beds. A seasonal cycle, opposing the dry periods to the others, was observed.Thus, it seems that the use of the mangrove habitat by the fishes is optimized through a complete reorganization of communities in terms of species composition whereas the overall number and biomass remain stable. This model remains valid even for the most constraining biota of the mangrove ecosystem inhabited by a small number of well adapted species.     

Pseudomonas aeruginosa B-band O-antigen chain length is modulated by Wzz (Ro1).

The wbp gene cluster, encoding the B-band lipopolysaccharide O antigen of Pseudomonas aeruginosa serotype O5 strain PAO1, was previously shown to contain a wzy (rfc) gene encoding the O-antigen polymerase. This study describes the molecular characterization of the corresponding wzz (rol) gene, responsible for modulating O-antigen chain length. P. aeruginosa O5 Wzz has 19 to 20% amino acid identity with Wzz of Escherichia coli, Salmonella enterica, and Shigella flexneri. Knockout mutations of the wzz gene in serotypes O5 and O16 (which has an O antigen structurally related to that of O5) yielded mutants expressing O antigens with a distribution of chain lengths differing markedly from that of the parent strains. Unlike enteric wzz mutants, the P. aeruginosa wzz mutants continued to display some chain length modulation. The P. aeruginosa O5 wzz gene complemented both O5 and O16 wzz mutants as well as an E. coli wzz mutant. Coexpression of E. coli and P. aeruginosa wzz genes in a rough strain of E. coli carrying the P. aeruginosa wbp cluster resulted in the expression of two populations of O-antigen chain lengths. Sequence analysis of the region upstream of wzz led to identification of the genes rpsA and himD, encoding 30S ribosomal subunit protein S1 and integration host factor, respectively. This finding places rpsA and himD adjacent to wzz and the wbp cluster at 37 min on the PAO1 chromosomal map and completes the delineation of the O5 serogroup-specific region of the wbp cluster.     

Coloboma Hyperactive Mutant Mice Exhibit Regional and Transmitter-Specific Deficits in Neurotransmission

Abstract: The mouse mutant coloboma ( Cm /+), which exhibits profound spontaneous hyperactivity and bears a deletion mutation on chromosome 2, including the gene encoding synaptosomal protein SNAP-25, has been proposed to model aspects of attention-deficit hyperactivity disorder. Increasing evidence suggests a crucial role for SNAP-25 in the release of both classical neurotransmitters and neuropeptides. In the present study, we compared the release of specific neurotransmitters in vitro from synaptosomes and slices of selected brain regions from Cm /+ mice with that of +/+ mice. The release of dopamine (DA) and serotonin (5-HT) from striatum, and of arginine vasopressin and corticotropin-releasing factor from hypothalamus and amygdala is calcium-dependent. Glutamate release from and content in cortical synaptosomes of Cm /+ mice are greatly reduced, which might contribute to the learning deficits in these mutants. In dorsal striatum of Cm /+ mutants, but not ventral striatum, KCI-induced release of DA is completely blocked and that of 5-HT is significantly attenuated, suggesting that striatal DA and 5-HT deficiencies may be involved in hyperactivity. Further, although acetylcholine failed to induce hypothalamic corticotropin-releasing factor release from Cm /+ slices, restraint stress increased plasma corticosterone levels in Cm /+ mice to a significantly higher level than in +/+ mice, suggesting an important role for arginine vasopressin in hypothalamic-pituitary-adrenal axis activation. These results suggest that reduced SNAP-25 expression may contribute to a region-specific and neurotransmitter-specific deficiency in neurotransmitter release.